COVID-19 Vaccine Research Articles

Estimated number of COVID-19 deaths averted by vaccination in Belgium

Abstract Background Vaccination campaigns have been rolled out globally to limit the impact of COVID-19 on severe health outcomes, including mortality. We aimed to estimate the number of averted deaths by COVID-19 vaccination in the Belgian population aged ≥65 years, between January 2021 and January 2023. Methods Nationwide data on COVID-19 infections, vaccinations and all-cause mortality were individually linked. We estimated Vaccine Effectiveness against COVID-19 mortality (VE) in persons having received a vaccine dose in the last 6 months using a Cox proportional hazards model adjusted for age, sex, time since vaccination, previous infection, comorbidities, province and income. COVID-19 death was defined as a death within 1-7 weeks after a positive SARS-CoV-2 laboratory-test. Based on obtained VE estimates, vaccine coverage and national COVID-19 mortality data, we estimated the number of averted deaths (expected deaths without vaccinating minus the reported deaths). Results By January 31st 2023, 11,033 COVID-19 deaths have been reported in Belgium. The average vaccine coverage was 48% during alpha, 85% during delta and 63% during omicron dominance. VE was estimated at 0-59 days after vaccination, for 65-79 year and ≥80 year-olds respectively, at 65% (58%-60%) and 35% (28%-41%) during Alpha, at 84% (82%-87%) and 79% (77%-81%) during Delta and at 83% (80%-85%) and 71% (68%-73%) during Omicron dominance. We estimated 10,042 deaths averted (range: 8,917-11,188) among the Belgian population aged ≥65 years, representing a 48% reduction (range 45%-50%) in the expected deaths. Out of 10,042 averted deaths, the majority was averted during Delta (47%; 4,670) or Omicron dominance (43%; 4,366), compared to during Alpha dominance (10%; 1,006). Conclusions Vaccinating against COVID-19 led to an important reduction in COVID-19-related mortality among the Belgian population ≥65 years, in particular during Delta and Omicron dominance, underscoring the effectiveness of vaccines against mortality. Key messages • Vaccinating against COVID-19 led to an important reduction of 48% in COVID-19-related mortality among the Belgian population ≥65 years, in particular during Delta and Omicron dominance. • Vaccine effectiveness against COVID-19 mortality was estimated as high in the Belgian population ≥65 years (range: 71-84%) during Delta and Omicron dominance, also among elderly over 80 years.

Restoring trust in vaccination through collective engagement with key populations in Eastern Europe

Abstract Issue/problem COVID-19 vaccination rates remained below 50% in Moldova, North Macedonia, and Serbia, especially among vulnerable populations like pregnant women and those with chronic diseases. This was strengthened by a lack of targeted communication and training for healthcare workers, and COVID-19 fatigue. Strategies to increase vaccine demand and confidence are a global priority, especially among vulnerable populations. Description of the solution From May 2022 to April 2024, the USAID MOMENTUM Routine Immunization Transformation and Equity project employed behavior integration to design a social and behavior change strategy, centering on vaccination as a part of a healthy lifestyle. It was implemented through continuing medical education (CME) and community engagement (CE) workshops with vulnerable populations, supplemented by cross-country learning exchanges. The outcomes provide a framework for public health initiatives aimed at boosting vaccine uptake through innovative, behavior-based methods. Results 1,618 healthcare professionals, able to reach 2.5 to 4.8 million patients, received training in immunization, COVID-19 vaccines, and quality health service, and 99% indicated confidence in applying the knowledge. 265 CE workshops, engaging 4,079 patients, increased awareness and addressed concerns related to vaccination. Of 3,223 patients who were followed up, 47% reported setting an appointment with their doctor regarding vaccination, 27% discussed vaccination with their partners, and 7% proceeded to receive the COVID-19 vaccine. Lessons Behavior Integration helped address key barriers to vaccination and informed the design of strategies (i.e. situating COVID-19 vaccination as part of a healthy lifestyle). Establishing trust with healthcare providers and patients through collective engagement improved health behaviors. Focusing on health as a wider priority helped re-establish the significance of vaccination as part of a healthy lifestyle. Key messages • Behavior science and behavior integration helped identify and address barriers, as well as design tailored interventions to improve vaccination demand and confidence. • Collective engagement, focused on integration of COVID-19 vaccination as part of a healthy lifestyle, achieved results through addressing vaccine hesitance from both sides of the equation.

Cultural filters in processing information on COVID vaccines among minoritized groups in London, UK

Abstract Introduction Vaccination coverage among minoritized groups, including migrants, is low in the United Kingdom. Cultural factors are often cited as barriers, yet the broader impact of minoritization on vaccine acceptance remains understudied. We explored the intersection of culture with individual, familial, and systemic factors in shaping trust and perceptions of COVID-19 vaccines in East London, UK. Methods We conducted focus group discussions (n = 6) and interviews (n = 19) with individuals from minoritized backgrounds in East London to elicit their perceptions and experiences of COVID-19 and the vaccination programme. Thematic analysis was used to identify individual, social, and systemic factors influencing the processing of perceived value of information on COVID vaccines. Findings Culture was rarely cited as an explicit barrier to vaccine uptake. Instead, participants’ linked their perceived vulnerability and immunity to COVID-19 with age, sex and health status. Information about COVID vaccines was processed and acted upon in the context of gendered family dynamics and support. Community identity, gatekeepers and social networks further influenced the perceived legitimacy of information received. Some participants voiced how their minoritized status shaped trust/mistrust in the national health system’s and government’s delivery of the COVID-19 information and vaccination campaigns Conclusions Unpacking cultural filters is crucial for addressing vaccine-related information barriers in minoritized groups. Going beyond mere language translation, tailored communication materials should address social enablers and systemic barriers. Further, closer collaboration between community gatekeepers and healthcare professionals to facilitate optimal use of these materials is needed to improve vaccine uptake. Key messages • Culture should not be assumed to be the main factor contributing to non-adherence and non-uptake of public health vaccine. • Vaccine uptake can be improved by healthcare workers and key community gate-keepers working collaboratively with minoritized groups.

From hesitancy to decision: shifts from intentions to uptake of Influenza and COVID-19 vaccines

Abstract Background Vaccine hesitancy is context-related and risks coverage. In a context of growing hesitancy, this study aims to characterize and identify factors underlying shifts in Influenza and COVID-19 vaccines intention and uptake. Methods Questionnaires were administered to a random sample of the 60+ years old Portuguese population (n = 1400), before (Q1) and at the end of the campaign (Q2). Sociodemographic, clinical data and intention to Influenza/COVID-19 vaccine uptake, using a Likert-scale (0-2: refusal; 3-7: hesitancy; 8-10: acceptance), were assessed on Q1. On Q2, self-reported vaccination status and motives. A logistic regression was performed to identify underlying factors. Results COVID-19 vaccine: 26.2% of those reporting acceptance went for non-uptake (214/818), stating low susceptibility/severity and fear of side effects. Factors associated were not having chronic disease (OR 2.07, p<.05) and age 60-64 (OR 4.16, p<.05). 25.5% of those who refuse went for vaccine uptake (27/106), stating self-initiative. Age 65 + (OR 43.82, p<.05) was associated with the shift; 56.4% of the hesitant individuals went for non-uptake (154/273). Higher education associates with non-uptake (OR 0.53, p<.05). Influenza vaccine: 11.5% of reported acceptance went for non-uptake (100/873), stating low susceptibility/severity. Associated factors were age 60-64 (OR 5.85, p<.05), not having chronic diseases (OR 2.64, p<.05) and living alone (OR 2.34, p<.05). 23.4% of those refusing decided for vaccine uptake (29/124), stating self-initiative/risk awareness. Associated factor was age 60-64 (OR 6.41, p<.05). 69.5% of hesitancy went for uptake (139/200). Chronic disease associates with non-uptake (OR 0.26, p<.05). Conclusions Intention is a good predictor but not decisive for uptake. This research provides better understanding of shifts in intention versus vaccine uptake, as well as factors and motives for hesitancy, allowing more robust interventions ahead of a vaccination campaign. Key messages • For the Influenza vaccine, 13% of individuals reporting acceptance or refusal changed their mind. From the group reporting hesitancy, 70% decided for vaccine uptake. • For the COVID-19 vaccine, 26% of individuals reporting acceptance or refusal changed their mind. From the group reporting hesitancy, 56% decided for non-vaccine uptake.

Determinants of COVID-19 vaccination acceptance based on the novel Omale INDEPT FORCIS Framework and recommendations for subsequent pandemics: a qualitative study among community members in Ebonyi state, Nigeria

BackgroundThe unprecedented COVID-19 pandemic has become an endemic disease of global public health importance. Mass COVID-19 vaccination has been an essential global control strategy amidst challenges of limited acceptance. Because of globalization, COVID-19/similar diseases vaccination acceptance and the determinants in any particular setting are important global public health issues. Using a novel and pragmatic framework, this study explored determinants of COVID-19 vaccination acceptance among community members during the pandemic in Ebonyi state, Nigeria, and made policy-relevant recommendations on how to increase vaccination acceptance in subsequent outbreaks/pandemics.MethodsThis qualitative study was based on the novel and pragmatic Individual Experiences and Perceptions and Complacency, Confidence, Convenience, and Compulsion (Four ‘Cis’) Determinants of Vaccination Acceptance Conceptual Framework – Omale INDEPT FORCIS Framework. On April 26 and 27, 2022, 20 semi-structured face-to-face focus group discussions were conducted in local language and pidgin English with 100 purposively selected consenting/assenting community members aged 15 years and above who had resided in the community for at least one year. Data was analysed using deductive (with some inductive) thematic analytic approach.ResultsThe many, diverse, and significant determinants of COVID-19 vaccination acceptance found were factors that were individual-related (individual experiences and perceptions and knowledge about COVID-19, COVID-19 vaccine/vaccination, and the vaccination process/system, sociodemographic, individual’s condition (e.g. pregnancy)); COVID-19-related (factuality, transmissibility, frequency, severity, fatality); COVID-19 vaccine/vaccination-related (safety/side-effects, effectiveness, speedy production); COVID-19 vaccination process/system-related (real availability/accessibility); family, group, and other individual-related (experiences and perceptions and actions); and broader local, national, international, and global (LONING) context-related (socio-political, economic, historic, health system factors). The broader LONING contextual factors included the unprecedented disinformation/conspiracy theories, non-sustained COVID-19 risk/behaviour change communication, enforcement and non-enforcement or termination of peculiar control policies/measures (lockdowns, social/physical distancing, use of face mask etc.), mandatory COVID-19 vaccination policies, provision of incentives, past experiences regarding the Ebola viral disease outbreak, (un)trustworthiness of the Nigerian health system and her international/global partners, and the (un)trustworthiness of the governments in Nigeria and bad/good governance, inclusive of the failure of the Ebonyi state government to distribute the COVID-19 palliatives to the people during the lockdowns.ConclusionThe evidence illuminates complex and interrelated, specific underlying, and peculiar policy-relevant LONING determinants of COVID-19 vaccination acceptance and emphasizes the need for concerted and comprehensive LONING strategies (involving all the relevant LONING stakeholders/policy makers) in addressing these determinants to increase vaccination acceptance among community members in subsequent outbreaks/pandemics in Ebonyi state/Nigeria and similar settings.

Estimating the impact of the COVID-19 vaccination programme in Ireland: December 2021-March 2023

Abstract Background In Autumn 2023, COVID-19 booster vaccines were offered to all those aged ≥50 years in Ireland. There was concern that vaccine fatigue would impact uptake. We aimed to quantify the direct impact of the COVID-19 vaccination programme on averted outcomes in individuals aged ≥50 years, during a period of Omicron variant dominance, to inform vaccination strategy and public health communication. Methods We conducted a retrospective observational study from December 2021 to March 2023 in Ireland. We considered as averted outcomes symptomatic SARS-CoV-2 presentations to primary care, emergency department (ED) presentations, hospitalisations, intensive care unit (ICU) admissions and deaths due to COVID-19. We used an adapted formula from other vaccine impact published studies, including national data on notified outcomes, vaccine coverage data and vaccine effectiveness (VE) estimates, sourced from the WHO’s live systematic VE review, to estimate the count and prevented fraction of outcomes in ≥ 50-year-olds averted by the COVID-19 vaccination programme. The number of expected outcomes in the absence of vaccination was calculated by summing the counts of outcomes observed and outcomes averted. Results Between December 2021 and March 2023, the COVID-19 vaccination programme averted 48,551 symptomatic presentations to primary care (36% of expected), 9,517 ED presentations (53% of expected), 102,160 hospitalisations (81% of expected), 3,303 ICU admissions (89% of expected) and 15,985 deaths (87% of expected). Conclusions During Omicron dominance, the COVID-19 vaccination programme averted symptomatic and severe outcomes, including deaths due to COVID-19, underscoring the benefits of COVID-19 vaccination. In the context of vaccine fatigue emerging as an important public health issue in Ireland and internationally, these findings can inform future COVID-19 booster vaccination programmes and communication about the reason for and importance of COVID-19 vaccination. Key messages • The COVID-19 vaccination programme in Ireland prevented illness and death in people aged ≥50-years. Vaccination therefore protected population health and the healthcare system. • These findings can be used to inform future COVID-19 vaccination policies, planning for winter, pandemic preparedness and communisation about the importance of ongoing COVID-19 vaccination programmes.

Prevalence and sociodemographic correlates of COVID-19 vaccine acceptance in 20 European countries

Abstract Our study aimed to analyze the prevalence and socio-economic factors associated with COVID-19 vaccine hesitancy using individual data from representative national samples of 20 European countries. Data from round 10 of the European Social Survey, collected from May 2021 to September 2022, were analyzed. Prevalence (with a 95% confidence interval (CI 95%)) of participants’ intention to get vaccinated against COVID-19 was calculated. Crude differences in vaccine hesitancy proportions across sociodemographic strata were assessed using the Chi-square test. There were 31,771 adult participants (46.0 % men). The percentage of those hesitant (i.e. those who were not already vaccinated and intended not to be) toward the COVID-19 vaccine was 18.0% (CI 95% 17.6 - 18.4). Men and women were equally hesitant (18.0% vs. 18.0%, p = 0.93). There were differences between those under 40 (22.9%), adults between 40 and 59 (18.1%), and those over 60 (14.3%, p < 0.001). The unemployed had a higher proportion of hesitancy (32.9%) compared to the employed (17.4%), retirees (14.8%), and students (21.1%, p < 0.001). People living in rural areas have higher levels of hesitancy compared to those in urban areas (19.3% vs. 17.3%, p < 0.001). The estimates indicate that the highest prevalence of vaccine hesitancy was in Bulgaria (61.6%), Slovenia (40.4%) and Slovakia (30.7%), while Iceland (2.3%), Portugal (3.6%) and Italy (4.0%) had the lowest. Our study confirms high prevalence and high variability of hesitancy towards COVID-19 vaccines in Europe and identify groups for potential targeted interventions.

COVID-19 vaccine associated myocarditis in Norway - a nationwide validation study

Abstract Background The SARS-CoV-2 pandemic led to worldwide initiation of vaccination campaigns. The new mRNA vaccines were unexpectedly associated with vaccine-associated myocarditis (VAM). The incidence and severity of VAM has not been validated in a nation-wide and well-defined population. From December 2020 onwards the mRNA vaccines Comirnaty and Spikevax have been in widespread use in Norway. The National Patient Register (NPR) includes all hospital contacts with corresponding diagnostic codes (ICD-10), and all vaccinations are registered in the Norwegian Immunization Register (SYSVAK). Purpose We aimed to identify and validate all cases of suspected COVID-19 VAM in Norway during the national vaccination campaign between 2020-22. Methods We identified all cases of myocarditis acquired within 90 days of a COVID-19 vaccination through linkage of diagnostic codes for myocarditis in NPR and vaccination data in SYSVAK. Cases were included from December 2020 through April 2022. We assessed medical records, cardiac imaging, and biochemistry to retrospectively validate all myocarditis cases. The Brighton Criteria (international criteria for myocarditis diagnosis following immunization with defining levels of diagnostic certainty) were used to confirm the VAM diagnosis. Results From December 2020 to April 2022, 4 114 750 unique subjects (2 036 792 men and 2 077 958 women, median age first dose 47 years) above 16 years of age, received 10 915 098 unique doses of COVID-19 vaccines (8 651 703[79%] Comirnaty and 2 263 395[21%] Spikevax). Of 277 cases of myocarditis identified in NPR<90 days after receiving a COVID-19 vaccine, 176(64%) were validated as VAM (78 definite, 90 probable, and 8 possible VAM). Among the patients with VAM, 137(78%) were men with median age 30(IQR 24-47) years, and 39(22%) were women with median age 54(IQR 32-65) years. There were 4 cases of VAM per 100 000 vaccinated subjects: 7 per 100 000 men and 2 per 100 000 women. Sixty-three percent of VAM occurred after the second mRNA vaccine dose. There were 3.3 cases of VAM per 100 000 unique doses of Spikevax compared to 1.1 per 100 000 unique doses of Comirnaty. The most common time interval from vaccination to VAM was 3 days and occurred in 30 patients (17.3% of VAM, 93% men), and 34% of VAM (90% men) occurred during the first 5 days from vaccination(Figure). Median duration of hospital stay was 4(IQR 3-5) days, with only 7(4%) patients needing intensive care and 1 myocarditis related patient death during hospitalization. Conclusions In this unique nationwide study including all COVID-19 vaccinated subjects in Norway from 2020-22 we found 4 cases of VAM per 100 000 vaccinated subjects. The majority of VAM occurred in young men. Interestingly, women presented later than men with VAM and most frequently at middle to older age. The occurrence of this unexpected serious adverse event underscores the importance of large studies in broad populations in future vaccine programs.

COVID-19 vaccine effectiveness and hybrid immunity in the respiratory season of 2022-23 in Hungary

Abstract Background There has been an increase in COVID-19 vaccine hesitancy among the general population, accompanied by a decline in confidence that vaccines provide adequate protection. We estimated the effectiveness of the COVID-19 vaccines (CVE) and hybrid immunity against medically attended COVID-19 during the 2022-2023 respiratory season in Hungary. Methods We conducted a test-negative design study involving 68 GPs. Patients aged ≥18 years presenting with acute respiratory infection were swabbed. Cases and controls were patients testing positive and negative for SARS-CoV-2 by RT-PCR, respectively. Exposure was defined as having received at least one COVID-19 booster dose, taking into account the time since the last vaccination. CVE was estimated using logistic regression, adjusted for symptom onset date, age, chronic condition and sex. Results We included 247 cases and 1073 controls in the analysis. 196 samples were sequenced, and Omicron BA.5, BQ.1 and XBB.1 were the most frequent sub-variants. The CVE was 52.9% (95% CI: 15.2-73.9%), and 72.3% (95% CI: 32.0-88.7%) in the 18-59, and 60+-year-old population who received the final dose within the past year, respectively. Self-reported COVID-19 in the previous 60-365 days did not confer protection against reinfection, however, when combined with booster vaccination, it reduced the risk of COVID-19 by 63.0% (95% CI: −28.0-89.3%) and 87.6% (95% CI: 26.4-97.9%) among the 18-59 and 60+ age groups, respectively. Conclusions Booster vaccination within one year after the last dose confers significant protection against symptomatic infection, particularly among the elderly. Those who have previously been infected with SARS-CoV-2 may also benefit from booster vaccinations. Key messages • COVID-19 booster campaigns must be intensified, focusing mainly on the elderly. • Providing clear guidance on the timing and target groups of vaccination and emphasising the benefits of vaccination can help to achieve higher coverage.

Vaccination status and long COVID symptoms among patients hospitalized with COVID-19: the WHF COVID-19 Long-term Study

Abstract Background COVID-19 vaccinations have been found to be effective in reducing the severity of COVID-19 infection and in-hospital deaths; however, insufficient evidence exists about the effect of vaccination on long term morbidity and mortality after hospitalization in patients from low- and middle-income countries. Methods The global WHF COVID-19 Long-Term Follow-up Study recruited 2,504 COVID-19 hospitalized patients from 26 collaborating sites in 16 countries between January 2022 - June 2023. Patients were followed up , at 1, 3, 6, and 9-12 months post-discharge to examine short- and long-term physical and psycho-social outcomes. A standardised questionnaire was used to collect data on demographics, pre-existing comorbidities, COVID-19 symptoms on admission, vaccination status, and outcomes at discharge, including persisting symptoms, new onset hypertension or diabetes, major adverse cardiovascular events (MACE), and mortality. We compared persistent long COVID symptoms, MACE, and mortality outcomes up to one year by COVID-19 vaccination status. Results The majority of study participants were Asians (78%), males (56%) with a mean (SD) age of 59.2 (19.9) years and from low- and middle-income (65%), upper middle-income (20%) and high-income (15%) countries. The most commonly reported comorbidities were hypertension: 54% and diabetes: 38%. Approximately two-thirds of the patients had received at least one dose of COVID-19 vaccination prior to hospitalization. Unvaccinated patients were more likely to present with dyspnea (60% vs 53%, p-value<0.001) and acute respiratory infection (15% vs 9%, p-value<0.001) during hospitalization. Unvaccinated patients also had twice the in-hospital mortality rate, compared with vaccinated patients (6% vs 3%, p-value<0.001). Unvaccinated patients had a greater incidence of MACE (23% vs 18%, p-value=0.016) during hospitalization and across all follow-up visits. Unvaccinated patients also had a higher mortality rate across all follow-up visits (mortality at one year post-discharge 14% vs 10%, p<0.001). At the 9-12 month follow-up, about a quarter of the patients had at least one long COVID symptom, but unvaccinated patients had a higher rate of long COVID symptoms, including fatigue (23% vs 14%, p<0.001), palpitations (17% to 7%, p-value<0.001), and anxiety (13% to 7%, p=0.002). Conclusions Our data highlight the long-term protective effect of COVID-19 vaccination on reducing morbidity and mortality among COVID-19 patients after hospital discharge. However, a substantial proportion of COVID-19 vaccinated patients still showed persistent long COVID symptoms (22%) and mortality (10%). Future research is needed to investigate individual- and health system-level factors contributing to poor health outcomes post-COVID-19 infection.

A Machine Learning Approach to Identifying Risk Factors for Long COVID-19

Long-term sequelae of coronavirus disease 2019 (COVID-19) infection are common and can have debilitating consequences. There is a need to understand risk factors for Long COVID-19 to give impetus to the development of targeted yet holistic clinical and public health interventions to reduce its associated healthcare and economic burden. Given the large number and variety of predictors implicated spanning health-related and sociodemographic factors, machine learning becomes a valuable tool. As such, this study aims to employ machine learning to produce an algorithm to predict Long COVID-19 risk, and thereby identify key predisposing factors. Longitudinal cohort data were sourced from the UK’s “Understanding Society: COVID-19 Study” (n = 601 participants with past symptomatic COVID-19 infection confirmed by serology testing). The random forest classification algorithm demonstrated good overall performance with 97.4% sensitivity and modest specificity (65.4%). Significant risk factors included early timing of acute COVID-19 infection in the pandemic, greater number of hours worked per week, older age and financial insecurity. Loneliness and having uncommon health conditions were associated with lower risk. Sensitivity analysis suggested that COVID-19 vaccination is also associated with lower risk, and asthma with an increased risk. The results are discussed with emphasis on evaluating the value of machine learning; potential clinical utility; and some benefits and limitations of machine learning for health science researchers given its availability in commonly used statistical software.

Co-administration of COVID-19 and flu vaccines in healthcare workers: results from three campaigns

Abstract The COVID-19 pandemic, along with seasonal influenza, highlights the need for innovative public health strategies. Co-administering COVID-19 and influenza vaccines offers advantages for healthcare workers (HCWs), streamlining vaccination efforts and enhancing public health resilience. Recent evidence supports the safety and efficacy of this approach, endorsed by health authorities worldwide. However, its acceptance remains a concern. This study explores HCWs’ acceptance of vaccine co-administration in three campaigns post the introduction of the anti-SARS-CoV-2 vaccine. During three consecutive flu seasons from October 2021 to January 2024, a cross-sectional study was conducted in a large Italian teaching hospital. Data for 2021/2022, 2022/2023 and 2023/2024 were compared, focusing on healthcare workers present in all datasets. McNemar’s test examined changes in acceptance of co-administration. In addition, a conditional logistic regression model was designed to assess the determinants of co-administration through the vaccination campaigns in the three years. During these vaccination campaigns 7457 HCWs were observed (62.78% women, median age 43). Co-administration surged, particularly in 2022/2023, showing a 280.71% increase, consistent across all professional categories (p < 0.001). Controlling for gender and professional category, acceptance of coadministration showed a significant association respectively with “open days” twice a month (OR 2.9 CI [2.7; 3.6]) and a hospital vaccination clinic two days a week on weekdays (OR 4.5 CI [4.1; 5.4]) compared to conducting vaccinations at a clinic open everyday during the campaign period; no association was highlighted with age. This study investigates a facet of an increasingly significant topic, demonstrating that co-administering vaccines for SARS-CoV-2 and influenza is emerging as an effective strategy in annual vaccination campaigns, thanks to its safety and the streamlining of logistical and organizational processes. Key messages • The co-administration of vaccines offers a promising strategy to enhance vaccination rates among healthcare workers. • By identifying factors influencing acceptance, it aims to inform targeted interventions for maximizing vaccine uptake and public health resilience.

England RCT of air filtration to prevent respiratory infections (including covid-19) in care homes

Abstract Context There is evidence that portable high-efficiency-particulate-air (HEPA) filtration units remove microbial particles from the air, but it is unclear whether this is sufficient to reduce infections in care home residents. Objectives To investigate the effectiveness of portable HEPA filtration units for winter respiratory infection episode reduction in care home residents. Study design and analysis: Cluster controlled trial with intention-to-treat analysis. Setting: 90 residential care homes for older adults in England. Population: Residents expected to reside in the care home for ≥1 month. Intervention care homes: Five HEPA filtration units in communal rooms and one HEPA filtration unit in 10 to 16 bedrooms. Control care homes: Usual care. Outcome measures: The primary outcome is the number of symptomatic winter respiratory infection episodes recorded by care home staff. Secondary outcomes: other infection measures; falls /near falls; laboratory confirmed infections; hospitalisations; and staff sickness. Process evaluation to assess intervention acceptability and implementation. Results Care homes were randomised between January 2022 and February 2024, 43 to intervention and 47 to usual care. Respectively, in intervention and control group care homes: 43% and 45% provided nursing care; 87% and 87% dementia care; and median (IQR) number of communal rooms were 4 (3-5) in both groups. 1126 residents were consented, of whom 31 (3%) moved away; 151 (13%) died; and 5 stopped participating. Primary outcome data is 98% complete with 175,318 'resident days' symptom data collected. Comparing intervention and control group residents: median (IQR) age was 88 (81-92) and 88 (82-92) years; 33% and 43% were receiving nursing care; 58% and 57% had dementia; frailty scores were 6 (4-7) and 6 (5-7); 94% and 94% received influenza; and 97% and 95% COVID vaccines. Conclusions Final analytic results of this world-first RCT will be available for the conference. Key messages • This world-first RCT using HEPA filters in care homes will report the evidence of effectiveness of respiratory infection episode reduction in care home residents. • The trial will inform policy makers about the effectiveness, acceptability and implementation of HEPA filters in care homes.

Income transfer and COVID-19 pandemic in Brazil: wrong and right at the same time

Abstract To alleviate the effects of socioeconomic inequalities and of the fall in economic activity on vulnerable populations during the COVID-19 pandemic, many countries have implemented or expanded income distribution programs. Brazil, amid the political and economic 2020 crisis, exacerbated by the pandemic, established Emergency Aid (EA). This longitudinal ecological study aimed to analyze whether the availability of EA contributed to the reduction of morbidity and mortality due to COVID-19 in the Brazilian 5,570 municipalities, from March 2020 to December 2021. The theoretical model considered as control covariates socioeconomic, sociodemographic and morbidity characteristics and access to health services, including COVID-19 testing availability and vaccination. Classical variable selection methods were applied considering the theoretical model, culminating in the adjustment of Bayesian hierarchical models with the inclusion of spatial and temporal effects. First dose COVID-19 vaccine coverage and EA had a protective effect against hospitalization (RR = 0.982 and RR = 0.986) and mortality (RR = 0.978 and RR = 0.976) due to COVID-19 in Brazil, when controlled by socioeconomic variables, access to health services and spatial-temporal effects. The results highlight the important role of income transfer in morbidity and mortality due to the disease, however, the way in which EA was implemented in Brazil presented a series of problems, the main ones being discontinued payment of aid, reduction in values throughout the duration of the benefit, in addition to the use of public resources to pay people who did not meet the eligibility criteria. Such problems might not have happened if the federal government had maintained the registration structure of Bolsa Familia Program (BFP), which did not happen. Furthermore, vaccination was started late for several reasons, that is, its role in reducing morbidity and mortality could have been even greater if started as soon as it become available. Key messages • Even with planning and execution problems, income transfer and specific vaccination were important in reducing COVID-19 morbidity and mortality in Brazil during the COVID-19 pandemic. • Income transfer during the COVID-19 pandemic in Brazil was not done in the best way possible, due to discontinued payment, reduction in values and payment to not eligible people.

Vaccination Coverage among Institutionalized Elderly Population: A Case Study in Cascais, Portugal

Abstract Vaccination stands as a cornerstone of public health, significantly reducing the morbidity and mortality associated with infectious diseases. However, the aging demographic, with declining homeostasis and immunosenescence, presents new challenges. Those residing in nursing homes face heightened risks of infectious diseases due to proximity and interactions with multiple staff members. In Portugal, elderly vaccination against tetanus/diphtheria (Td) is integrated into the National Vaccination Program, with additional official recommendations for pneumococcal (Pn), seasonal influenza, and COVID-19 vaccinations. Specific vaccination campaigns in nursing homes for influenza and COVID-19 are coordinated by Public Health Units. This study aimed to assess the vaccination coverage for these vaccines among the institutionalized elderly in Cascais municipality and evaluate the implementation of official recommendations. A survey of nursing homes in Cascais was conducted, and the vaccination status of residents was assessed through electronic records in February 2024. Statistical analysis was performed. Vaccination status for each vaccine was considered valid if individuals had received at least one dose of Pn13 or Pn23, a Td vaccine dose within the last 10 years, and vaccinations against influenza and COVID-19 within the last 6 months. Among 2189 institutionalized elderly in Cascais, 87% were vaccinated against both influenza and COVID-19, 39% against Td, and 17% against pneumococcal disease. While influenza and COVID-19 vaccination coverage is high, the tetanus/diphtheria vaccination rate is low, and pneumococcal vaccination is very low, despite official recommendations. This population remains at increased risk for preventable diseases. Monitoring vaccination status and implementing targeted vaccination campaigns are crucial for increasing coverage, realizing health and economic benefits and preventing severe diseases. Key messages • Vaccination is essential for safeguarding the health of institutionalized elderly populations. There is a need for targeted interventions to address preventable diseases and protect these individuals. • Monitoring vaccination status and implementing targeted campaigns are critical for increasing coverage and realizing health and economic benefits among elderly populations in nursing homes.

Sex-specific immune responses to COVID-19 vaccination in end-stage renal disease patients

Abstract Background End-stage renal disease (ESRD) patients have muted memory B cell formation and reduced humoral responses to COVID-19 vaccination; however, early innate immune responses have yet to be characterized. Sex-stratification is also limited in COVID-19 vaccination research. Methods We collected blood before (BD1) and 1-4 days post-dose 1 (PD1) of BNT162b2 vaccination for RNA-sequencing in ESRD patients (n = 35 BD1; 18 PD1) and healthy controls (HC) (n = 31 BD1; 30 PD1). Additionally, 20 plasma cytokines were quantified in ESRD patients (n = 39 BD1, 35 PD1) and HC (34 BD1, 15 PD1). Results Transcriptional profiling of vaccine responses identified 125 significantly differentially expressed genes (DEG) (padj<0.04) in ESRD patients and 107 DEGs (padj<0.05) in HC. 71 DEGs were shared, 54 unique to ESRD, and 36 unique to HC. DEG, pathway analyses, and cytokine responses in the combined dataset showed ESRD patients were more inflamed than HC at baseline, with an elevated inflammatory cytokine profile compared to HC. These results were driven by female ESRD patients where IL-2, IL-10, and IP-10 were more significant in females (p < 0.001) compared to males (p < 0.01). While IL-6, IFN-γ, IL-13, eotaxin, were exclusively associated in females (p < 0.05). Healthy females also had a stronger immunological response to vaccination compared to healthy males. Conclusions Despite baseline inflammation, ESRD patients were able to mount similar early immune responses to vaccination as HC, with females in both populations more reactogenic than males. Sex-stratification is recommended for ongoing immunological research to better understand unique responses to COVID-19 vaccination. Key messages • End-stage renal disease patients have similar early innate immune responses to COVID-19 vaccination as healthy controls. • Sex-stratification is important to identify unique immunological responses that may be leveraged for sex-specific vaccination strategies.

Empowering Educators: Italian Nurses’ Knowledge, Attitudes, Practices, and Vaccine Hesitancy

Abstract Background Vaccine hesitancy (VH) among healthcare workers is a prevalent global phenomenon and a public health concern. The study aims were i) identifying knowledge, attitudes, and practices (KAP); ii) estimating the prevalence of VH regarding recommended vaccines for healthcare workers (HWs). Methods Multicenter cross-sectional study of an Italian sample of nurses and nursing students. Following a systematic review (PROSPERO ID:CRD42020212252), a validated questionnaire was used (Cronbach’s alpha=0.82). Two multivariable logistic regression model were built to identify predictors of (1) VH to the recommended vaccine for HWs; (2) acceptance of the fourth COVID-19 vaccine dose. Results 226 participants were enrolled (169 nurses; 57 students). Regarding KAP: only four nurses (1.8%) had adequate knowledge among vaccine recommended for HWs, whereas 30% (N = 66) reported never having recommended vaccinations during clinical practice. 106 (46%) nurses/students reported VH for at least one of the vaccines recommended for HWs - high levels of VH were recorded for influenza vaccination (N = 88,38.9%) and fourth COVID-19 vaccine dose (N = 100,44.3%). At the multivariable analysis, (1) significant associations with highest levels of VH were found for nurses who reported having at least one child (OR:5.42, 95%CI: 1.64-17.89) and who had not received any dose of influenza vaccination in the last 5 years (OR:13.25, 95%CI: 5.29-33.16). Lowest odds of VH was found for nurses employed in Primary Health Care (OR:0.17, 95%CI: 0.03-0.98); (2) routinely recommending vaccinations during practice (OR:0.38, 95% CI: 0.15-0.95) was associated with acceptance of fourth COVID-19 vaccine dose. Conversely, reliance on social media as the primary information source seemed to be a predictor of COVID-19 vaccine refusal (OR:2.05 95% CI: 1.31-3.20). Conclusions Preliminary results identified predictors of VH among nurses, offering insights for organizations to effectively tailor public health interventions. Key messages • High levels of vaccine hesitancy among nurses towards recommended vaccines for healthcare workers pose a threat to patient safety. • Empowering ‘educators’ through focused public health interventions is essential to address factors contributing to vaccine hesitancy among healthcare workers.

Impact of primary course COVID-19 vaccination on hospitalizations in Belgium, a Bayesian approach

Abstract Background The Belgian COVID-19 primary course vaccine rollout was prioritized for individuals aged 18-64 years with underlying health conditions (increased risk of severe COVID-19), over their peers of the same age. This led to a 32-day earlier vaccination of prioritized individuals. In this research, we assessed the impact of vaccine rollout prioritization on hospitalizations for COVID-19 in Belgium between April 1st 2021 and June 30th 2021. Methods The sample consisted of the Belgian population aged 18-64 years. Individuals were classified by their priority status according to underlying health conditions and by vaccination status, creating weekly changing cohorts. The hospitalization probability was estimated by cohort using a national COVID-19 hospital surveillance. Two counterfactual scenarios were considered: (1) a no vaccination scenario and (2) a scenario in which the vaccine administration occurred at random in both cohorts (a vaccine rollout without prioritization). We used a Bayesian model to jointly estimate cohort-specific hospitalization probability and scenario outcomes. Results Out of the sample of 5,448,534 individuals, 22.65 % was prioritized. By May 1st, vaccination coverage was 18% and 2% within the prioritized and the non-prioritized cohort. In scenario 2, coverage within the prioritized was 6% by May 1st. There were 6968 hospitalizations reported through the hospital survey. Our initial scenario-outcomes indicated a reduction in hospitalizations of 3203 (95%CI[2548;3858]) and 919 (95%CI[406;1433]) by the vaccination prioritization, compared to scenarios 1 and 2, respectively. Conclusions This research provides insights in the impact of vaccination in a pandemic context in Belgium. We report a significant reduction in simulated COVID-19 hospitalization by vaccine prioritization compared to at random vaccination and no vaccination at all. Currently, we are investigating the effect of age-dependent vaccination next to at random vaccination. Key messages • The prioritised vaccination campaign in Belgium led to a significant reduction in hospitalizations. • Prioritisation based on underlying health conditions is an important public health measure.

Vaccination campaign implementation in Madagascar: a Dynamic Sustainability Framework approach

Abstract Background The COVID-19 pandemic has highlighted the need for equitable and timely access to vaccination. Limited evidence is available on how to implement vaccination campaigns (VCs) that are sustainable and responsive to changes in real-world health policy and practice contexts. We present lessons learned from the implementation of a COVID-19 VC in the Boeny region of Madagascar. Methods Informed by the Dynamic Sustainability Framework, VC implementation was continuously reviewed during multisectoral stakeholder feedback rounds, key informant interviews, and problem-solving meetings to identify and put key adaptations throughout the campaign process into practice. Outcome indicators include pre- and post-VC vaccine hesitancy and trends in vaccine doses deployed were analyzed using generalized linear models. Results Key adaptations of the implementation strategy included community-led awareness-raising and outreach activities also in remote areas, strengthening VC through the training of 340 staff, and addressing gaps identified in the cold chain, waste management, vaccine transportation, and IT equipment. Overall, 24888 COVID-19 vaccines were administered in six months. Changes in campaign strategy increased the number of doses administered by 8% (RR = 1.08; CI 95%: 1.01; 1.15) per week. No changes in vaccine hesitancy post-VC were observed in an unvaccinated population(Δ = 0.02, CI 95%: -0.04; 0.08). Conclusions Collaborative and dynamic multi-sectoral VC strategies that combine healthcare-based approaches with pro-active outreach and community-led awareness-raising activities are essential in increasing vaccine uptake in limited-resource settings. Our findings show that despite boosting vaccination coverage, such initiatives may not have an impact on COVID-19 vaccine hesitancy at the community level Key messages • Multisectoral stakeholder collaboration and engagement are key to successful vaccination campaign implementation. • A Dynamic Sustainability Framework approach can be effective in ensuring a continuous fit between campaign and its setting.

ChineseCVD: a web-based Chinese-specifi c cardiovascular risk calculator incorporating long COVID, COVID-19vaccination, SGLT2i and PCSK9i treatment effects

Abstract Background Web-based risk prediction tools for cardiovascular diseases are crucial for providing rapid risk estimates for busy clinicians, but there is none available specifically for Chinese subjects. This study developed ChineseCVD, a risk calculator for cardiovascular disease. Methods Adult patients attending government-funded family medicine clinics in Hong Kong between 1st January 2000 and 31st December 2003 were included. The primary outcome was major adverse cardiovascular events (MACE) defined as a composite of myocardial infarction, heart failure, transient ischaemic attacks/ischaemic strokes, and cardiovascular mortality. Results A total of 155,066 patients were used as the derivation cohort. Over a median follow-up of 16.1 (11.6-17.8) years, 31,061 (20.44%) had MACE. Cox regression identified male gender, age, comorbidities, cardiovascular medications, systolic and diastolic blood pressure, and laboratory test results (neutrophil-lymphocyte ratio, creatinine, ALP, AST, ALT, HbA1c, fasting glucose, triglyceride, LDL and HDL) as significant predictors of the above outcomes. ChineseCVD further incorporates the impact of smoking status, COVID-19 infection, number of COVID-19 vaccination doses, and modifier effects of newest medication classes of PCSK9i and SGLT2i. The calculator enables clinicians to demonstrate to patients how risks vary with different medications. Conclusions The ChineseCVD risk calculator enables rapid web-based risk assessment for adverse cardiovascular outcomes, thereby facilitating clinical decision-making at the bedside or in the clinic.