Adjusted Vaccine Effectiveness Research Articles

End of 2022/23 Season Influenza Vaccine Effectiveness in Primary Care in Great Britain.

The 2022/23 influenza season in the United Kingdom saw the return of influenza to prepandemic levels following two seasons with low influenza activity. The early season was dominated by A(H3N2), with cocirculation of A(H1N1), reaching a peak late December 2022, while influenza B circulated at low levels during the latter part of the season. From September to March 2022/23, influenza vaccines were offered, free of charge, to all aged 2-13 (and 14-15 in Scotland and Wales), adults up to 49 years of age with clinical risk conditions and adults aged 50 and above across the mainland United Kingdom. End-of-season adjusted vaccine effectiveness (VE) estimates against sentinel primary-care attendance for influenza-like illness, where influenza infection was laboratory confirmed, were calculated using the test negative design, adjusting for potential confounders. Results In the mainland United Kingdom, end-of-season VE against all laboratory-confirmed influenza for all those > 65 years of age, most of whom received adjuvanted quadrivalent vaccines, was 30% (95% CI: -6% to 54%). VE for those aged 18-64, who largely received cell-based vaccines, was 47% (95% CI: 37%-56%). Overall VE for 2-17 year olds, predominantly receiving live attenuated vaccines, was 66% (95% CI: 53%-76%). The paper provides evidence of moderate influenza VE in 2022/23.

Vaccine Effectiveness Against Long COVID in Children.

Vaccination reduces the risk of acute coronavirus disease 2019 (COVID-19) in children, but it is less clear whether it protects against long COVID. We estimated vaccine effectiveness (VE) against long COVID in children aged 5 to 17 years. This retrospective cohort study used data from 17 health systems in the RECOVER PCORnet electronic health record program for visits after vaccine availability. We examined both probable (symptom-based) and diagnosed long COVID after vaccination. The vaccination rate was 67% in the cohort of 1 037 936 children. The incidence of probable long COVID was 4.5% among patients with COVID-19, whereas diagnosed long COVID was 0.8%. Adjusted vaccine effectiveness within 12 months was 35.4% (95 CI 24.5-44.7) against probable long COVID and 41.7% (15.0-60.0) against diagnosed long COVID. VE was higher for adolescents (50.3% [36.6-61.0]) than children aged 5 to 11 (23.8% [4.9-39.0]). VE was higher at 6 months (61.4% [51.0-69.6]) but decreased to 10.6% (-26.8% to 37.0%) at 18-months. This large retrospective study shows moderate protective effect of severe acute respiratory coronavirus 2 vaccination against long COVID. The effect is stronger in adolescents, who have higher risk of long COVID, and wanes over time. Understanding VE mechanism against long COVID requires more study, including electronic health record sources and prospective data.

Effectiveness of one dose of killed oral cholera vaccine in an endemic community in the Democratic Republic of the Congo: a matched case-control study

A global shortage of cholera vaccines has increased the use of single-dose regimens, rather than the standard two-dose regimen. There is sparse evidence on single-dose protection, particularly in children. In 2020, a mass vaccination campaign was conducted in Uvira, an endemic urban setting in eastern Democratic Republic of the Congo, resulting in largely single-dose coverage. We examined the effectiveness of a single-dose of the oral cholera vaccine Euvichol-Plus in this high-burden setting. In this matched case-control study, we recruited individuals with medically attended confirmed cholera in the two cholera treatment facilities in the city of Uvira. The control group consisted of age-matched, sex-matched, and neighbourhood-matched community individuals. We recruited across two distinct periods: Oct 14, 2021, to March 10, 2022 (12-17 months after vaccination), and Nov 21, 2022, to Oct 18, 2023 (24-36 months after vaccination). Study staff administered structured questionnaires to all participants to capture demographics, household conditions, potential confounding variables, and vaccination status. The odds of vaccination for the case and control groups were contrasted in conditional logistic regression models to estimate unadjusted and adjusted vaccine effectiveness. We enrolled 658 individuals with confirmed cholera and 2274 matched individuals for the control group. 99 (15·1%) individuals in the case group were younger than 5 years at the time of vaccination. The adjusted single-dose vaccine effectiveness was 52·7% (95% CI 31·4 to 67·4) 12-17 months after vaccination and 44·7% (24·8 to 59·4) 24-36 months after vaccination. Although protection in the first 12-17 months after vaccination was similar for children aged 1-4 years and older individuals, the estimate of protection in children aged 1-4 years appeared to wane during the third year after vaccination (adjusted vaccine effectiveness 32·9%, 95% CI -30·7 to 65·5), with CIs spanning the null. A single dose of Euvichol-Plus provided substantial protection against medically attended cholera for at least 36 months after vaccination in this cholera-endemic setting. Although the evidence provides support for similar levels of protection in young children and others in the short term, protection among children younger than 5 years might wane significantly during the third year after vaccination. Wellcome Trust and Gavi, the Vaccine Alliance.

Effectiveness of SARS-CoV-2 primary vaccines and boosters in patients with type 2 diabetes mellitus in Hungary (HUN-VE 4 Study)

IntroductionType 2 diabetes mellitus is a risk factor for severe COVID-19 infection and is associated with increased risk of complications. The present study aimed to investigate effectiveness and persistence of...

Covid-19 and influenza vaccine effectiveness against associated hospital admission and death among individuals over 65 years in Norway: A population-based cohort study, 3 October 2022 to 20 June 2023

BackgroundCo-circulation of SARS-CoV-2 and influenza virus can lead to double epidemics and increased pressure on health systems. To evaluate the effect of both vaccines, we estimated the adjusted vaccine effectiveness (aVE) of influenza and Covid-19 vaccines against related severe disease in the elderly population in Norway during the 2022/2023 season. MethodsIn this population-based cohort study, we included data from the Emergency preparedness register for Covid-19 (Beredt C19) on all individuals ≥ 65 years living in Norway between 3 October 2022 and 20 June 2023. Using Cox-proportional hazard models, we estimated aVE of both influenza and Covid-19 vaccines (bivalent BA.1 and BA.4–5) against associated hospitalisation and death. Vaccine status was included as a time-varying covariate and all models were adjusted for potential confounders, including the other vaccine. ResultsWe identified 2,437 influenza-associated hospitalisations and 178 deaths, alongside 5,824 Covid-19-associated hospitalisations and 621 deaths. The aVE was highest in the first three months after receiving either vaccine. Against influenza-associated hospitalisation the aVE was 34 % (26 %–42 %) among 65–79-year-olds and 40 % (30 %–48 %) among ≥ 80-year-olds, and 6.6 % (−64 %–47 %) and 37 % (0.5 %–61 %) against influenza-associated death, respectively. The aVE against Covid-19-associated hospitalisation was 65 % (61 %–69 %) among 65–79-year-olds and 55 % (49 %–60 %) among ≥ 80-year-olds (compared to having received the vaccine ≥ 180 days ago). Similarly, the aVE against Covid-19-associated death was 68 % (48 %–80 %) and 78 % (65 %–86 %), respectively. For Covid-19 we show a reduction in aVE with time since dose. ConclusionCovid-19 and influenza vaccines reduced the risk of severe disease in the same high-risk population. Ensuring high uptake of both vaccines could thus limit the overall health care burden.

Effectiveness of COVID-19 vaccines in Ecuador: A test-negative design

BackgroundThe COVID-19 pandemic poses a significant global health threat, characterized by high morbidity, severity, and the emergence of concerning variants. Latin America has been greatly affected, with high infection and mortality rates. Vaccination plays a crucial role in mitigating severe disease and controlling the pandemic. This study aims to assess the effectiveness of COVID-19 vaccines in preventing SARS-CoV-2 severe acute respiratory infections (SARI) in hospitalized vaccination target groups in Ecuador. MethodsThis is a test-negative design study. We used data reported through sentinel surveillance of SARI between May 2021 and March 2022 in Ecuador. Patients with case criteria of SARI and hospitalized for a minimum of 24 hours were included in the study. Cases were defined as patients with SARI with a positive RT-qPCR test for SARS-CoV-2 and controls were those with a negative result. Information on vaccination status was obtained from the national vaccination registry, a valid dose of vaccination was considered when it was administered at least 14 days prior to symptom onset. Vaccine effectiveness (VE) (1-OR/OR) was calculated using a logistic regression. ResultsA total of 1,277 patients were included in the analysis of VE. The adjusted vaccine effectiveness (aVE) in preventing hospitalization, adjusted for sex, age group, presence of one or more comorbidities, and period of the predominance of the omicron variant, was 44.5% for the partial primary schedule, 74.7% for the complete primary schedule, and 79.9% for the complete primary schedule plus booster doses. The aVE in avoiding ICU admissions was close to 80% with both the complete primary schedule and the booster doses, and in avoiding deaths, the aVE was 89% and 98%, respectively. ConclusionsIn Ecuador, COVID-19 vaccination prevents hospitalizations, ICU admissions, and deaths. The effectiveness of the vaccines improves with more doses, offering increased protection across all age groups.

COVID-19 vaccine effectiveness against hospitalisation and death of people in clinical risk groups during the Delta variant period: English primary care network cohort study

COVID-19 vaccines have been shown to be highly effective against hospitalisation and death following COVID-19 infection. COVID-19 vaccine effectiveness estimates against severe endpoints among individuals with clinical conditions that place them at increased risk of critical disease are limited. We used English primary care medical record data from the Oxford-Royal College of General Practitioners Research and Surveillance Centre sentinel network (N>18 million). Data were linked to the National Immunisation Management Service database, Second Generation Surveillance System for virology test data, Hospital Episode Statistics, and death registry data. We estimated adjusted vaccine effectiveness (aVE) against COVID-19 infection followed by hospitalisation and death among individuals in specific clinical risk groups using a cohort design during the delta-dominant period. We also report mortality statistics and results from our antibody surveillance in this population. aVE against severe endpoints was high, 14-69d following a third dose aVE was 96.4% (95.1%-97.4%) and 97.9% (97.2%-98.4%) for clinically vulnerable people given a Vaxzevria and Comirnaty primary course respectively. Lower aVE was observed in the immunosuppressed group: 88.6% (79.1%-93.8%) and 91.9% (85.9%-95.4%) for Vaxzevria and Comirnaty respectively. Antibody levels were significantly lower among the immunosuppressed group than those not in this risk group across all vaccination types and doses. The standardised case fatality rate within 28 days of a positive test was 3.9/1000 in people not in risk groups, compared to 12.8/1000 in clinical risk groups. Waning aVE with time since 2nd dose was also demonstrated, for example, Comirnaty aVE against hospitalisation reduced from 96.0% (95.1-96.7%) 14-69days post-dose 2-82.9% (81.4-84.2%) 182days+ post-dose 2. In all clinical risk groups high levels of vaccine effectiveness against severe endpoints were seen. Reduced vaccine effectiveness was noted among the immunosuppressed group.

Impact of vaccination on infection or death from COVID-19 in individuals with laboratory-confirmed cases: Case-control study.

The objective of this study is to estimate the effectiveness of COVID-19 vaccines in people treated within the social security system whose vaccination status was reported to the epidemiological surveillance system. Case-control study. This was a case-control study conducted. The records of individuals with suspected cases of COVID-19 registered in the epidemiological surveillance system between February 1 and June 30, 2021, were studied. RT-qPCR was performed to determine SARS-CoV-2 infection; those with a positive result were considered cases, and those with a negative result were considered controls. The ratio between cases and controls was 1:1.3. The crude and adjusted vaccine effectiveness was considered the prevention of symptomatic infection and death and calculated as the difference between the dose and the risk, with a survival analysis among vaccinated people. A total of 94,416 individuals were included, of whom 40,192 were considered cases and 54,224 controls; 3,781 (4.00%) had been vaccinated against COVID-19. Vaccination also proved to be a protective factor against COVID-19, especially in the population who received a second dose (OR = 0.31; 95% CI 0.28-0.35). With the application of the vaccine, there was a protective effect against mortality (OR = 0.76; 95% CI 0.66-0.87). Disease prevention was higher for the BNT162-2 mRNA vaccine (82%) followed by the ChAdOx1 vaccine (33%). In the survival analysis, vaccination provided a protective effect. There was a positive impact of vaccines for the prevention of symptomatic COVID-19, with a second dose generating greater efficacy and a reduction in deaths.

Changing Characteristics of Children With COVID-19 in Colorado Admitted During Different Variant Periods.

Data are lacking on the impact of different severe acute respiratory syndrome coronavirus 2 variants in children and on pediatric vaccine effectiveness. We examined differences among children requiring hospital admission associated with coronavirus disease 2019 (COVID-19) during wild type, Delta and Omicron variant periods and calculated vaccine effectiveness at preventing symptomatic hospitalization during the Delta and Omicron variant periods. We conducted a retrospective review of children younger than 21 years of age hospitalized with symptomatic COVID-19. Characteristics were compared between variant periods using Kruskal-Wallis or generalized Fisher exact tests. We estimated vaccine effectiveness in preventing symptomatic hospitalization. We included 115 children admitted during the wild type period, 194 during Delta and 226 during the Omicron periods. Median age (years) decreased (12.2 wild type, 5.9 Delta, 1.3 Omicron periods, P < 0.0001) over time. Children were less likely to have a comorbid condition, including diabetes or obesity, and had shorter admissions during Omicron compared with the wild type and Delta periods. Intensive care unit admissions and respiratory support requirements were highest during the Delta period (P = 0.05). Among children ≥12 years, adjusted vaccine effectiveness at preventing symptomatic hospitalization was 86% during Delta and 45% during Omicron periods. Children hospitalized with COVID-19 during later variant periods were younger and less likely to have comorbidities. Children admitted during the Delta variant period required more intensive care and respiratory support compared to other variant periods. Vaccination was less effective at preventing symptomatic hospital admission during the Omicron period compared to the Delta period.

Vaccine Effectiveness of JYNNEOS against Mpox Disease in the United States

BackgroundIn the United States, more than 30,000 cases of mpox (formerly known as monkeypox) had occurred as of March 1, 2023, in an outbreak disproportionately affecting transgender persons and gay, bisexual, and other men who have sex with men. In 2019, the JYNNEOS vaccine was approved for subcutaneous administration (0.5 ml per dose) to prevent mpox infection. On August 9, 2022, an emergency use authorization was issued for intradermal administration (0.1 ml per dose); however, real-world effectiveness data are limited for either route.MethodsWe conducted a case–control study based on data from Cosmos, a nationwide Epic electronic health record (EHR) database, to assess the effectiveness of JYNNEOS vaccination in preventing medically attended mpox disease among adults. Case patients had an mpox diagnosis code or positive orthopoxvirus or mpox virus laboratory result, and control patients had an incident diagnosis of human immunodeficiency virus (HIV) infection or a new or refill order for preexposure prophylaxis against HIV infection between August 15, 2022, and November 19, 2022. Odds ratios and 95% confidence intervals were estimated from conditional logistic-regression models, adjusted for confounders; vaccine effectiveness was calculated as (1−odds ratio for vaccination in case patients vs. controls)×100.ResultsAmong 2193 case patients and 8319 control patients, 25 case patients and 335 control patients received two doses (full vaccination), among whom the estimated adjusted vaccine effectiveness was 66.0% (95% confidence interval [CI], 47.4 to 78.1), and 146 case patients and 1000 control patients received one dose (partial vaccination), among whom the estimated adjusted vaccine effectiveness was 35.8% (95% CI, 22.1 to 47.1).ConclusionsIn this study using nationwide EHR data, patients with mpox were less likely to have received one or two doses of JYNNEOS vaccine than control patients. The findings suggest that JYNNEOS vaccine was effective in preventing mpox disease, and a two-dose series appeared to provide better protection. (Funded by the Centers for Disease Control and Prevention and Epic Research.)

Effectiveness of an inactivated SARS-CoV-2 vaccine in children and adolescents: a large-scale observational study

Policymakers urgently need evidence to adequately balance the costs and benefits of mass vaccination against COVID-19 across all age groups, including children and adolescents. In this study, we aim to assess the effectiveness of CoronaVac's primary series among children and adolescents in Chile. We used a large prospective national cohort of about two million children and adolescents 6-16 years to estimate the effectiveness of an inactivated SARS-CoV-2 vaccine (CoronaVac) in preventing laboratory-confirmed symptomatic SARS-CoV-2 infection (COVID-19), hospitalisation, and admission to an intensive care unit (ICU) associated with COVID-19. We compared the risk of individuals treated with a complete primary immunization schedule (two doses, 28 days apart) with the risk of unvaccinated individuals during the follow-up period. The study was conducted in Chile from June 27, 2021, to January 12, 2022, when the SARS-CoV-2 Delta variant was predominant but other variants of concern were co-circulating, including Omicron. We used inverse probability-weighted survival regression models to estimate hazard ratios of complete immunization over the unvaccinated status, accounting for time-varying vaccination exposure and adjusting for relevant demographic, socioeconomic, and clinical confounders. The estimated adjusted vaccine effectiveness for the inactivated SARS-CoV-2 vaccine in children aged 6-16 years was 74.5% (95% CI, 73.8-75.2), 91.0% (95% CI, 87.8-93.4), 93.8% (95% CI, 87.8-93.4) for the prevention of COVID-19, hospitalisation, and ICU admission, respectively. For the subgroup of children 6-11 years, the vaccine effectiveness was 75.8% (95% CI, 74.7-76.8) for the prevention of COVID-19 and 77.9% (95% CI, 61.5-87.3) for the prevention of hospitalisation. Our results suggest that a complete primary immunization schedule with the inactivated SARS-CoV-2 vaccine provides effective protection against severe COVID-19 disease for children 6-16 years. Agencia Nacional de Investigación y Desarrollo (ANID) Millennium Science Initiative Program and Fondo de Financiamiento de Centros de Investigación en Áreas Prioritarias (FONDAP).

The Waning of BNT162b2 Vaccine Effectiveness for SARS-CoV-2 Infection Prevention over Time: A Test-Negative Study in Health Care Professionals of a Health Department from January 2021 to December 2021.

The duration of protection of vaccines against SARS-CoV-2 infection has been evaluated in previous studies, but uncertainty remains about the persistence of effectiveness over time and the ideal timing for booster doses. Therefore, the aim of this study was to evaluate BNT162b2 vaccine effectiveness against SARS-CoV-2 infection in health care workers (HCWs) at a tertiary hospital depending on time elapsed since the completion of a two-dose vaccination regimen. We conducted a case-control with negative test study between 25 January and 12 December 2021 that included 1404 HCWs who underwent an active infection diagnostic test (AIDT) to rule out SARS-CoV-2 infection due to COVID-19 suspicion or prior close contact with patients diagnosed with COVID-19. The adjusted vaccine effectiveness (aVE) for the prevention of SARS-CoV-2 infection 12 to 120 days after completing the full two-dose vaccination regimen was 91.9%. Then, aVE decreased to 63.7% between 121 to 240 days after completing the full two-dose regimen and to 37.2% after 241 days since the second dose. Vaccination against SARS-CoV-2 infection in HCWs remains highly effective after 12 to 120 days have elapsed since the administration of two doses of the BNT162b2 vaccine; however, effectiveness decreases as time elapses since its administration.

Effectiveness of mRNA COVID-19 Vaccines in Adolescents Over 6 Months.

On June 4, 2021, Italy launched the coronavirus disease 2019 (COVID-19) vaccination of adolescents to slow down the COVID-19 spread. Although clinical trials have evaluated messenger ribonucleic acid (mRNA) vaccine effectiveness in adolescents, there is limited literature on its real-world effectiveness. Accordingly, this study aimed to estimate the effectiveness of mRNA COVID-19 vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and mild or severe COVID-19 in a cohort of Sicilian adolescents within a 6 month observation period. A retrospective cohort study was conducted with adolescents aged 12 to 18 years, residents of Sicily, who were followed from July 15 to December 31, 2021. SARS-CoV-2 infections, mild and severe COVID-19, and COVID-19-related intubation or deaths during the study period were compared between subjects vaccinated with 2 doses of mRNA vaccines and unvaccinated individuals. The Cox regression analysis, adjusted for age and sex, was performed to compare the 2 groups. Overall, the study included a total at-risk population of 274 782 adolescents with 61.4% of them having completed the vaccination cycle by the end of the study. Unvaccinated subjects had higher incidence rates of SARS-CoV-2 (1043 × 10 000 vs 158.7 × 10 000 subjects), mild COVID-19 (27.7 × 10 000 vs 1.8 × 10 000 subjects) and severe COVID-19 (1.41 × 10 000 vs 0 subjects) compared with the vaccinated population. The estimated adjusted vaccine effectiveness against SARS-CoV-2 infection was 71.2%, reaching 92.1% and 97.9% against mild and severe COVID-19, respectively. This study provides rigorous evidence of mRNA COVID-19 vaccines' effectiveness in protecting adolescents from both SARS-CoV-2 infection and COVID-19.

Effectiveness of Inactivated COVID-19 Vaccines against COVID-19 Caused by the SARS-CoV-2 Delta and Omicron Variants: A Retrospective Cohort Study.

Background: Real-world evidence on the effectiveness of inactivated vaccines against the Delta and Omicron (BA.2.38) variants remains scarce. Methods: A retrospective cohort study was conducted to estimate the adjusted vaccine effectiveness (aVE) of one, two, and three doses of inactivated vaccines in attenuating pneumonia, severe COVID-19, and the duration of viral shedding in Delta and Omicron cases using modified Poisson and linear regression as appropriate. Results: A total of 561 COVID-19 cases were included (59.2% Delta and 40.8% Omicron). In total, 56.4% (184) of Delta and 12.0% (27) of Omicron cases had COVID-19 pneumonia. In the two-dose vaccinated population, 1.4% of Delta and 89.1% of Omicron cases were vaccinated for more than 6 months. In Delta cases, the two-dose aVE was 52% (95% confidence interval, 39–63%) against pneumonia and 61% (15%, 82%) against severe disease. Two-dose vaccination reduced the duration of viral shedding in Delta cases, but not in booster-vaccinated Omicron cases. In Omicron cases, three-dose aVE was 68% (18%, 88%) effective against pneumonia, while two-dose vaccination was insufficient for Omicron. E-values were calculated, and the E-values confirmed the robustness of our findings. Conclusions: In Delta cases, two-dose vaccination within 6 months reduced pneumonia, disease severity, and the duration of viral shedding. Booster vaccination provided a high level of protection against pneumonia with Omicron and should be prioritized.

Effectiveness of Whole-Virus COVID-19 Vaccine among Healthcare Personnel, Lima, Peru.

In February 2021, Peru launched a COVID-19 vaccination campaign among healthcare personnel using an inactivated whole-virus vaccine. The manufacturer recommended 2 vaccine doses 21 days apart. We evaluated vaccine effectiveness among an existing multiyear influenza vaccine cohort at 2 hospitals in Lima. We analyzed data on 290 participants followed during February-May 2021. Participants completed a baseline questionnaire and provided weekly self-collected nasal swab samples; samples were tested by real-time reverse transcription PCR. Median participant follow-up was 2 (range 1-11) weeks. We performed multivariable logistic regression and adjusted for preselected characteristics. During the study, 25 (9%) participants tested SARS-CoV-2-positive. We estimated adjusted vaccine effectiveness at 95% (95% CI 70%-99%) among fully vaccinated participants and 100% (95% CI 88%-100%) among partially vaccinated participants. These data can inform the use and acceptance of inactivated whole-virus vaccine and support vaccination efforts in the region.

BNT162b2 vaccination reduced infections and transmission in a COVID-19 outbreak in a nursing home in Germany, 2021.

BackgroundA SARS‐CoV‐2 outbreak was detected in a nursing home in February 2021 after residents and staff had received two doses of BNT162b2 vaccine in January 2021.MethodsNursing home staff, long‐term residents and day‐care receivers were included in a retrospective cohort study. We calculated attack rates (AR), secondary AR (SAR) and their 95% binomial confidence interval (CI), and we compared them using Fisher's exact test or chi‐squared test, depending on the sample size. We used Poisson regression with robust error estimates to calculate vaccine effectiveness against SARS‐COV‐2 infections. We selected variables based on directed acyclic graphs. As a proxy for viral load at diagnosis, we compared the mean Ct values at diagnosis using t tests or Mann–Whitney U tests.ResultsThe adjusted vaccine effectiveness against infection was 56% (95% CI: 15–77%, p = 0.04). Ct values at diagnosis were higher when intervals after receiving the second vaccination were longer (>21 vs. ≤21 days: 4.48 cycles, p = 0.08). The SAR was 67% lower in households of vaccinated (2/9 [22.2%]) than of unvaccinated infected staff (12/18 [66.7%]; p = 0.046). Vaccination rates were lowest among staff with close physical contact to care‐receivers (46%). The highest AR in vaccinated staff had those working on wards (14%).ConclusionsVaccination reduced the risk for SARS‐CoV‐2 infection, viral load and transmission; however, non‐pharmaceutical interventions remain essential to reduce transmission of SARS‐CoV‐2 infections, even for vaccinated individuals. Vaccination coverage of staff ought to increase reduction of infections among themselves, their household members and residents.

Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, July–November 2021

BackgroundCOVID-19 vaccines have been crucial in the pandemic response and understanding changes in vaccines effectiveness is essential to guide vaccine policies. Although the Delta variant is no longer dominant, understanding vaccine effectiveness properties will provide essential knowledge to comprehend the development of the pandemic and estimate potential changes over time.MethodsIn this population-based cohort study, we estimated the vaccine effectiveness of Comirnaty (Pfizer/BioNTech; BNT162b2), Spikevax (Moderna; mRNA-1273), Vaxzevria (AstraZeneca; ChAdOx nCoV-19; AZD1222), or a combination against SARS-CoV-2 infections, hospitalisations, intensive care admissions, and death using Cox proportional hazard models, across different vaccine product regimens and age groups, between 15 July and 31 November 2021 (Delta variant period). Vaccine status is included as a time-varying covariate and all models were adjusted for age, sex, comorbidities, county of residence, country of birth, and living conditions. Data from the entire adult Norwegian population were collated from the National Preparedness Register for COVID-19 (Beredt C19).ResultsThe overall adjusted vaccine effectiveness against infection decreased from 81.3% (confidence interval (CI): 80.7 to 81.9) in the first 2 to 9 weeks after receiving a second dose to 8.6% (CI: 4.0 to 13.1) after more than 33 weeks, compared to 98.6% (CI: 97.5 to 99.2) and 66.6% (CI: 57.9 to 73.6) against hospitalisation respectively. After the third dose (booster), the effectiveness was 75.9% (CI: 73.4 to 78.1) against infection and 95.0% (CI: 92.6 to 96.6) against hospitalisation. Spikevax or a combination of mRNA products provided the highest protection, but the vaccine effectiveness decreased with time since vaccination for all vaccine regimens.ConclusionsEven though the vaccine effectiveness against infection waned over time, all vaccine regimens remained effective against hospitalisation after the second vaccine dose. For all vaccine regimens, a booster facilitated recovery of effectiveness. The results from this support the use of heterologous schedules, increasing flexibility in vaccination policy.

Effectiveness of first, second, and third COVID-19 vaccine doses in solid organ transplant recipients: A population-based cohort study from Canada

Limited data exists on the effectiveness of a third COVID‐19 vaccine dose in solid organ transplant recipients. We conducted a population‐based cohort study using linked healthcare databases from Ontario, Canada to answer this question. We included solid organ transplant recipients (n = 12,842) as of December 14, 2020, with follow‐up until November 28, 2021. We used an extended Cox proportional hazards model with vaccination status, including BNT162b2, mRNA‐1273, and ChAdOx1 vaccines, modeled as a time‐dependent exposure. Individuals started in the unvaccinated category (reference) and could contribute person‐time to first, second, and third doses. Over a median follow‐up of 349 days, 12.7% (n = 1632) remained unvaccinated, 54.1% (n = 6953) received 3 doses, and 488 (3.8%) tested positive for SARS‐CoV‐2 (of which 260 [53.3%] had a clinically important outcome [i.e., hospitalization or death]). Adjusted vaccine effectiveness against infection was 31% (95% CI: 2, 51%), 46% (95% CI: 21, 63%), and 72% (95% CI: 43, 86%) for one, two, and three doses. Vaccine effectiveness against clinically important outcomes was 38% (95% CI: 4, 61%), 54% (95% CI: 23, 73%), and 67% (95% CI: 11, 87%). Vaccine effectiveness in solid organ transplant recipients is lower than the general population, however, vaccine effectiveness improved following a third dose.

The effectiveness of mRNA vaccines to prevent SARS-CoV-2 infection and hospitalisation for COVID-19 according to the time elapsed since their administration in health professionals in the Valencian Autonomous Community (Spain)

The objective was to understand the effectiveness of the BNT162b2 and mRNA-1273 vaccines against SARS-CoV-2 in health professionals(HPs) in the Valencian Autonomous Community(Spain) who had completed a full vaccination regimen, both in terms of preventing infections and avoiding hospitalisations, according to the time elapsed since the vaccine administration.Case-controlled study with negative test results. HPs who had undergone at least one PCR or antigen(Ag) active infection diagnostic test(AIDT) to rule out SARS-CoV-2 infection between 25 January and 18 July 2021 were included. HPs with positive AIDT result were considered as cases and those with a negative result controls. Adjusted vaccine effectiveness(VEa) to prevent SARS-CoV-2 infection and its 95% confidence interval(95% CI) were calculated using the formula VEa = (1 − OR) × 100.The VEa for the prevention of SARS-CoV-2 infection 12 to 120 days after completing the full two-dose vaccine regimen was 91.6%(95%CI[89.6%,93.2%]) for the BNT162b2 vaccine and 95.2%(95%CI[88.3%,98.1%]) for the mRNA-1273 vaccine. After 120 days the VEa was 71.5%(95%CI[67.0%,75.5%]) for the BNT162b2 vaccine and 88.3%(95%CI[75.7,94.4%]) for the mRNA-1273 vaccine. The VEa for prevention of hospitalisation for COVID-19 for the complete two-dose regimen of mRNA vaccines (BNT162b2 and mRNA-1273) was 96.8%(95%CI[76.1%,99.6%]).The administration of the complete regimen of the BNT162b2 and mRNA-1273 vaccine against SARS-CoV-2 was highly effective for the prevention of COVID-19 cases in HPs when 12 to 120 days had elapsed since the second dose. However, said effectiveness decreased as time from the vaccine administration elapsed, although it was maintained for the prevention of hospitalisation of HPs.

COVID-19 vaccination for children aged 5–11 years

COVID-19 vaccination for children aged 5–11 years