Influenza Illness Research Articles

Systematic Review on Influenza Burden in Emerging Markets in 2018–2023—An Evidence Update to Guide Influenza Vaccination Recommendations

Background: Influenza is a contagious respiratory illness responsible for seasonal epidemics and with potential to cause pandemics. The decline in influenza-related studies published since 2018 resulted in data gaps, particularly in emerging markets. Methods: This systematic review searched for studies in six databases and gray literature sources to define the clinical burden of influenza and influenza-like illness (ILIs) and their associated sequelae among humans across emerging markets. Eligible studies were published in English, Spanish, or Chinese between January 2018 and September 2023 and conducted in Asia, the Middle East, Africa, and Latin America. Results: In total, 256 articles were included, mostly on lab-confirmed influenza infections (n = 218). Incidences of lab-confirmed influenza cases in Asia (range 540–1279 cases/100,000 persons) and Sub-Saharan Africa (range 34,100–47,800 cases/100,000 persons) were higher compared to Latin America (range 0.7–112 cases/100,000 persons) and the Middle East and North Africa (range 0.1–10 cases/100,000 persons). Proportions of lab-confirmed influenza cases and influenza-associated outcomes (i.e., hospitalization, ICU admission and death) varied widely across regions. Temporal variation in influenza trend was observed before and during the COVID-19 pandemic. Conclusions: In conclusion, influenza causes significant disease burden in emerging markets. Robust large real-world studies using a similar methodology are needed to have more accurate estimates and compare studies within age groups and regions. Continuous monitoring of influenza epidemiology is important to inform vaccine programs in emerging markets with heavy influenza disease burden.

Estimating Influenza Illnesses Averted by Year-Round and Seasonal Campaign Vaccination for Young Children, Kenya.

In Kenya, influenza virus circulates year-round, raising questions about optimum strategies for vaccination. Given national interest in introducing influenza vaccination for young children 6-23 months of age, we modeled total influenza-associated illnesses (inclusive of hospitalizations, outpatient illnesses, and non‒medically attended illnesses) averted by multiple potential vaccination strategies: year-round versus seasonal-campaign vaccination, and vaccination starting in April (Southern Hemisphere influenza vaccine availability) versus October (Northern Hemisphere availability). We modeled average vaccine effectiveness of 50% and annual vaccination coverage of 60%. In the introduction year, year-round vaccination averted 6,410 total illnesses when introduced in October and 7,202 illnesses when introduced in April, whereas seasonal-campaign vaccination averted 10,236 (October) to 11,612 (April) illnesses. In the year after introduction, both strategies averted comparable numbers of illnesses (10,831-10,868 for year-round, 10,175-11,282 for campaign). Campaign-style vaccination would likely have a greater effect during initial pediatric influenza vaccine introduction in Kenya; however, either strategy could achieve similar longer-term effects.

Influenza Vaccine Effectiveness Against Illness and Asymptomatic Infection in 2022-2023: A Prospective Cohort Study.

Previous estimates of vaccine effectiveness (VE) against asymptomatic influenza virus infection based on seroconversion have varied widely and may be biased. We estimated 2022-2023 influenza VE against illness and asymptomatic infection in a prospective cohort. In the HEROES-RECOVER cohort, adults at increased occupational risk of influenza exposure across 7 US sites provided weekly symptom reports and nasal swabs for reverse transcription-polymerase chain reaction (RT-PCR) influenza testing. Laboratory-confirmed influenza virus infections were classified as symptomatic (≥1 symptom) or asymptomatic during the week of testing. Participants reported demographic information and vaccination through surveys; most sites verified vaccination through medical record and immunization registry review. Person-time was calculated as days from the site-specific influenza season start (September-October 2022) through date of infection, study withdrawal, or season end (May 2023). We compared influenza incidence among vaccinated versus unvaccinated participants overall, by symptom status, and by influenza A subtype, using Cox proportional hazards regression adjusted for site and occupation. We estimated VE as (1 - adjusted hazard ratio) × 100%. In total, 269 of 3785 (7.1%) participants had laboratory-confirmed influenza, including 263 (98%) influenza A virus infections and 201 (75%) symptomatic illnesses. Incidence of laboratory-confirmed influenza illness among vaccinated versus unvaccinated participants was 23.7 and 33.2 episodes per 100 000 person-days, respectively (VE: 38%; 95% CI: 15%-55%). Incidence of asymptomatic influenza virus infection was 8.0 versus 11.6 per 100 000 (VE: 13%; 95% CI: -47%, 49%). Vaccination reduced incidence of symptomatic but not asymptomatic influenza virus infection, suggesting that influenza vaccination attenuates progression from infection to illness.

Contribution of immunoglobulin products in influencing seasonal influenza infection and severity in antibody immune deficiency patients receiving immunoglobulin replacement therapy.

Seasonal and pandemic influenza infection present a potential threat to patients with antibody deficiency. The acceptance and effect of the current recommendation for annual vaccination against influenza for patients with antibody deficiency is not well investigated and due to antigenic drift or shift the protective capacity of regular IgG replacement therapy (IgRT) is considered low. This narrative review considers the effect of influenza vaccination in immunodeficient patients and discusses available information on the effect of immunoglobulin products on seasonal influenza infectivity and severity in antibody deficiency patients receiving IgRT. The humoral immune response to seasonal influenza vaccination is reduced in patients with antibody immune deficiency. However, there is no evidence that the proportion of patients with primary antibody deficiency who develop influenza illness, and the severity of such illness, is increased when compared with the general population. The IgRT that patients receive has been shown to contain neutralizing antibodies as a consequence of past flu infections against both the hemagglutinin and neuraminidase surface proteins and other viral internal proteins of different influenza A virus strains. Studies have demonstrated not only significant levels of specific but also cross-reactive antibodies against seasonal influenza virus strains. Thus, despite the yearly changes in influenza viral antigenicity that occur, IgRT could potentially contribute to the protection of patients against seasonal influenza. Currently, only limited clinical data are available confirming a preventative effect of IgRT with respect to seasonal influenza infection. In conclusion, there is some evidence that IgRT could contribute to protection against seasonal influenza in patients with antibody-related immunodeficiency. However, additional clinical data are needed to confirm the extent and relevance of this protection and identify the main responsible virus targets of that protection.

Optimization of timing for maternal immunization to protect newborns from influenza infection

Objectives The primary objective of this systematic review was to identify the optimal timing for immunizing pregnant women to confer the most protection by reducing the incidence of laboratory-confirmed influenza or influenza-like illness in infants less than 6 months of age. Currently, there are gaps in research regarding the timing of administration during the gestational period to provide maximum immunogenicity to the infant. The research question being addressed is: ‘When considering immunization of pregnant mothers with the influenza vaccine, implementing a vaccination program during which trimester in pregnancy would optimize benefits for infants less than 6 months of age in terms of the incidence of laboratory-confirmed influenza and influenza-like illness?’ Design Systematic review/Meta-analysis Methods Randomized controlled trials (RCT’s) and observational studies comparing health outcomes of infants and children up to 6 months of age born to women who received inactivated influenza vaccine during pregnancy with mothers who did not receive the vaccine or received a control vaccine. The primary outcome was laboratory-confirmed influenza infection in infants. Secondary outcome measures included influenza –like illness diagnosed by a clinician and acute respiratory illness. Results 7 studies were included: 2 primary RCT’s and 5 observational studies (prospective and retrospective cohort studies).5 of the 7 studies were suitable to be included in the quantitative synthesis part and and were compared. Forrest plot analysis revealed that vaccinating pregnant mothers in the second and third trimester when compared with any trimester (1,2 and 3) (OR 0.18 vs. 0.65) conferred less protection, promoting vaccination in the first trimester. Conclusions Vaccinating pregnant mothers in the first trimester conferred greater protection to infants than any other trimester.

Interim Effectiveness Estimates of 2024 Southern Hemisphere Influenza Vaccines in Preventing Influenza-Associated Hospitalization - REVELAC-i Network, Five South American Countries, March-July 2024.

To reduce influenza-associated morbidity and mortality, countries in South America recommend annual influenza vaccination for persons at high risk for severe influenza illness, including young children, persons with preexisting health conditions, and older adults. Interim estimates of influenza vaccine effectiveness (VE) from Southern Hemisphere countries can provide early information about the protective effects of vaccination and help guide Northern Hemisphere countries in advance of their season. Using data from a multicountry network, investigators estimated interim VE against influenza-associated severe acute respiratory illness (SARI) hospitalization using a test-negative case-control design. During March 13-July 19, 2024, Argentina, Brazil, Chile, Paraguay, and Uruguay identified 11,751 influenza-associated SARI cases; on average, 21.3% of patients were vaccinated against influenza, and the adjusted VE against hospitalization was 34.5%. The adjusted VE against the predominating subtype A(H3N2) was 36.5% and against A(H1N1)pdm09 was 37.1%. These interim VE estimates suggest that although the proportion of hospitalized patients who were vaccinated was modest, vaccination with the Southern Hemisphere influenza vaccine significantly lowered the risk for hospitalization. Northern Hemisphere countries should, therefore, anticipate the need for robust influenza vaccination campaigns and early antiviral treatment to achieve optimal protection against influenza-associated complications.

Cost-Effectiveness of Influenza Vaccination in Healthy Children: A 10-Year Population-Based Study

Background/Objectives: Seasonal influenza annually puts a significant burden on the pediatric population, especially the youngest, causing severe illness and death. Additionally, associated healthcare costs cause a significant financial strain on healthcare systems. While vaccination is the most effective prevention method, its cost-effectiveness for healthy children remains unassessed. Methods: Using the Pedianet database spanning from 2009 to 2019, we analyzed influenza cases among 6-month-olds to 14-year-olds in Italy. Data included influenza-related medical visits, prescriptions, exams, emergency visits, hospitalizations, and costs. Adverse events and quality-adjusted life years (QALYs) were considered from the existing literature. A static decision-tree model compared annual vaccination strategies, assessing probabilities for influenza or influenza-like illnesses by vaccination status. Incremental cost-effectiveness ratios (ICERs) were calculated, along with sensitivity analyses and cost-effectiveness acceptability curve generation. Results: Mean total influenza costs for vaccinated children averaged EUR 18.6 (range 0–3175.9, including EUR 15.79 for the influenza vaccination), whereas costs for unvaccinated children were consistently lower at around EUR 4.6 (range 0–3250.1). The average ICER for years where vaccine and virus strains are matched was EUR 29,831 per QALY, which is below the EUR 40,000 threshold set by the Italian National Health Services. The ICER values range from EUR 13,736 (2017/2018) to EUR 72,153 (2013/2014). Averted influenza costs averaged EUR 23 per case, with fluctuations over the years. In most observed years, influenza vaccination was cost-effective from the healthcare providers’ standpoint. The exception was 2009–2010, due to a mismatch between vaccine and virus strains. Conclusions: This study highlights the economic viability of influenza vaccination, especially when virus and vaccine strains align. It demonstrates the potential of vaccination programs in preserving children’s health and well-being while managing healthcare costs.

Elevated body mass index is not significantly associated with reduced influenza vaccine effectiveness

Elevated body mass index (BMI) has been linked to severe influenza illness and impaired vaccine immunogenicity, but the relationship between BMI and clinical vaccine effectiveness (VE) is less well described. This secondary analysis of data from a test-negative study of outpatients with acute respiratory illness assessed BMI and VE against medically attended, PCR-confirmed influenza over seven seasons (2011–12 through 2017–18). Vaccination status was determined from electronic medical records (EMR) and self-report; BMI was estimated from EMR-documented height and weight categorized for adults as obesity (≥ 30 kg/m2), overweight (25–29 kg/m2), or normal and for children based on standardized z-scales. Current season VE by virus type/subtype was estimated separately for adults and children. Pooled VE for all seasons was calculated as 1—adjusted odds ratios from logistic regression with an interaction term for BMI and vaccination. Among 28,089 adults and 12,380 children, BMI category was not significantly associated with VE against outpatient influenza for any type/subtype. Adjusted VE against A/H3N2, A/H1N1pdm09, and B in adults ranged from 16–31, 46–54, and 44–57%, and in children from 29–34, 57–65, and 50–55%, respectively, across the BMI categories. Elevated BMI was not associated with reduced VE against laboratory confirmed, outpatient influenza illness.

Caregiver Burden among Patients with Influenza or Influenza-like Illness (ILI): A Systematic Literature Review.

Influenza and influenza-like illness (ILI) pose significant clinical and economic burdens globally each year. This systematic literature review examined quantitative studies evaluating the impact of patients' influenza/ILI on their caregivers' well-being, focusing on health-related quality of life (HRQoL), work productivity, and activity impairment. A comprehensive search across six databases, including the Cochrane Database of Systematic Reviews, Embase, MEDLINE via PubMed, Ovid, PsycNet, and Web of Science, yielded 18,689 records, of which 13,156 abstracts were screened, and 662 full-text articles were reviewed from January 2007 to April 2024. Thirty-six studies [HRQoL: 2; productivity: 33; both: 1] covering 22 countries were included. Caregivers of 47,758 influenza or ILI patients across 123 study cohorts were assessed in the review. The mean workday loss among caregivers ranged from 0.5 to 10.7 days per episode, influenced by patients' influenza status (positive or negative), disease severity (mild or moderate-to-severe), age, viral type (influenza A or B), and vaccination/treatment usage. The HRQoL of caregivers, including their physical and emotional well-being, was affected by a patient's influenza or ILI, where the severity and duration of a patient's illness were associated with worse HRQoL. This review shows that the consequences of influenza or ILI significantly affect not only patients but also their caregivers.

Continuous Monitoring of Heart Rate Variability in Free-Living Conditions Using Wearable Sensors: Exploratory Observational Study.

Wearable physiological monitoring devices are promising tools for remote monitoring and early detection of potential health changes of interest. The widespread adoption of such an approach across communities and over long periods of time will require an automated data platform for collecting, processing, and analyzing relevant health information. In this study, we explore prospective monitoring of individual health through an automated data collection, metrics extraction, and health anomaly analysis pipeline in free-living conditions over a continuous monitoring period of several months with a focus on viral respiratory infections, such as influenza or COVID-19. A total of 59 participants provided smartwatch data and health symptom and illness reports daily over an 8-month window. Physiological and activity data from photoplethysmography sensors, including high-resolution interbeat interval (IBI) and step counts, were uploaded directly from Garmin Fenix 6 smartwatches and processed automatically in the cloud using a stand-alone, open-source analytical engine. Health risk scores were computed based on a deviation in heart rate and heart rate variability metrics from each individual's activity-matched baseline values, and scores exceeding a predefined threshold were checked for corresponding symptoms or illness reports. Conversely, reports of viral respiratory illnesses in health survey responses were also checked for corresponding changes in health risk scores to qualitatively assess the risk score as an indicator of acute respiratory health anomalies. The median average percentage of sensor data provided per day indicating smartwatch wear compliance was 70%, and survey responses indicating health reporting compliance was 46%. A total of 29 elevated health risk scores were detected, of which 12 (41%) had concurrent survey data and indicated a health symptom or illness. A total of 21 influenza or COVID-19 illnesses were reported by study participants; 9 (43%) of these reports had concurrent smartwatch data, of which 6 (67%) had an increase in health risk score. We demonstrate a protocol for data collection, extraction of heart rate and heart rate variability metrics, and prospective analysis that is compatible with near real-time health assessment using wearable sensors for continuous monitoring. The modular platform for data collection and analysis allows for a choice of different wearable sensors and algorithms. Here, we demonstrate its implementation in the collection of high-fidelity IBI data from Garmin Fenix 6 smartwatches worn by individuals in free-living conditions, and the prospective, near real-time analysis of the data, culminating in the calculation of health risk scores. To our knowledge, this study demonstrates for the first time the feasibility of measuring high-resolution heart IBI and step count using smartwatches in near real time for respiratory illness detection over a long-term monitoring period in free-living conditions.

Potential anti-HIV and antitrypanosomal components revealed in Sorindeia nitidula via LC-ESI-QTOF-MS/MS

Sorindeia nitidula (Anacardiaceae) is used by traditional practitioners to treat influenza illnesses with cephalgia and febrile aches. However, the potential active ingredients for its remarkable antioxidant, anti-HIV and antitrypanosomal activities remain unexplored. The present study aims to evaluate the antioxidant, anti-HIV and antitrypanosomal activities of the ethyl acetate extract of S. nitidula (SN) in order to screen out the bioactive compounds and to analyze their possible mechanisms of action. Overall, 21 phenolic compounds were annotated, by using the MS and MS/MS information provided by the QTOF-MS. In vitro assays on the extract revealed potent antioxidant (IC50 = 0.0129 ± 0.0001 mg/mL), anti-HIV (IC50 = 1.736 ± 0.036 µM), antitrypanosomal (IC50 = 1.040 ± 0.010 µM) activities. Furthermore, SN did not present cytotoxic effect on HeLa cancer cell lines. The integrated strategy based on LC-ESI-QTOF-MS/MS provided a powerful tool and a multidimensional perspective for further exploration of active ingredients in S. nitidula responsible for the antioxidant, anti-HIV and antitrypanosomal activities.

Increased Risk of Acute Aortic Events following COVID-19 and Influenza Respiratory Viral Infections

Acute respiratory viral infections have been associated with an increased incidence of adverse cardiovascular events. However, it is unclear whether severe respiratory viral infections are associated with an increased risk of acute aortic syndromes (AAS). This study was designed to assess whether Coronavirus disease 2019 (COVID-19) and Influenza illnesses are associated with an increased incidence of subsequent AAS in the US population. We used the MarketScan database (2011-2021) to identify patients 18-99years of age without prior diagnosis of aortic pathology who were diagnosed with COVID-19 or Influenza. Identified patients were matched 1:1 by age and sex to control patients without COVID-19 or Influenza. The primary outcome was incidence of AAS (dissection, intramural hematoma, penetrating aortic ulcer, or aneurysm rupture) within 180-days of a viral infection. The association between infection and risk of developing an AAS was analyzed using multivariate Cox proportional hazards models. We identified 1,775,698 patients, including 779,229 (44%) with mild COVID-19, 42,141 (2%) with severe COVID-19, and 66,479 (4%) with Influenza that were matched to 887,849 (50%) control patients without COVID-19 or Influenza illnesses. A total of 164 patients experienced AAS within 6-months after diagnosis, which was highest among those after severe COVID-19. The predicted incidence of AAS was significantly higher among patients after severe COVID-19 (14.1 events/100,000 person-years), mild COVID-19 (13.3 events/100,000), and influenza (13.3 events/100,000) when compared to control patients (2.6 events/100,000). In risk-adjusted Cox regression models, severe COVID-19 (HR:5.4, 95% CI:2.8-10.4; P<0.01), mild COVID-19 (HR:5.1, 95% CI:3.3-7.7; P<0.01) and influenza (HR:5.1, 95% CI:2.6-9.7; P<0.01) diagnoses were associated with a significantly increased risk of AAS within 180-days when compared to matched controls. There is an increased risk of developing acute aortic event in the months following illness with Influenza or COVID-19. These data highlight the need to closely monitor at-risk patients following a viral respiratory infection.

Trivalent and quadrivalent seasonal influenza vaccine in adults aged 60 and older: a systematic review and network meta-analysis

ObjectivesTo compare the efficacy of influenza vaccines of any valency for adults 60 years and older.Design and settingSystematic review with network meta-analysis (NMA) of randomised controlled trials (RCTs). MEDLINE, EMBASE,...

Parental knowledge, attitudes, and practices toward vaccinating their children against influenza: a cross-sectional study from China.

Influenza infection is a health burden in children, and the influenza vaccine is an important prevention strategy for flu illness. Parents play a crucial role in children's influenza vaccination. The study aimed to assess parental knowledge, attitudes, and practices (KAP) related to influenza illness for their children and explore factors that may impact their decisions. This cross-sectional study was conducted in a tertiary hospital in Guangzhou from November 2022 to April 2023. Answers to KAP questions regarding influenza illness and vaccination were summed, with a total KAP score of 20. Univariate and multivariate logistic regression models and linear regression models were conducted to explore the factors associated with influenza vaccination. The results were presented as odds ratios (ORs), β, and 95% confidence intervals (CIs). Overall, 530 parents were respondents, of whom 162 (30.56%) had vaccinated their children during the past year. The mean KAP score (standard deviation) was 13.40 (3.57). Compared to parents who reported non-vaccinated for their children in the past year, the parents who reported an influenza vaccination have higher knowledge scores, attitude scores, practice scores, and total scores. Child body mass index, parental education level (under college), parental work (part-time), and more than two family members over 60 years old were negatively correlated with knowledge score. Child health condition and knowledge score were positively correlated with attitude score. Parental age was negatively associated with attitude score. Though high awareness about influenza illness and vaccination for parents, the coverage rate of influenza vaccination in children was lower in Guangzhou. Implementing public health policies is necessary to spread knowledge about influenza illness and vaccination and to promote the practice of receiving the influenza vaccine in children. Education campaigns would help change the attitudes of parents toward vaccinating their children against the flu.

Prevalence of influenza and other acute respiratory illnesses in patients with acute myocardial infarction in Bangladesh: A cross-sectional study.

Several studies imply that influenza and other respiratory illnesses could lead to acute myocardial infarction (AMI), but data from low-income countries are scarce. We investigated the prevalence of recent respiratory illnesses and confirmed influenza in AMI patients, while also exploring their relationship with infarction severity as defined by ST-elevation MI (STEMI) or high troponin levels. This cross-sectional study, held at a Dhaka tertiary hospital from May 2017 to October 2018, involved AMI inpatients. The study examined self-reported clinical respiratory illnesses (CRI) in the week before AMI onset and confirmed influenza using baseline real-time reverse transcription polymerase chain reaction (qRT-PCR). Of 744 patients, 11.3% reported a recent CRI, most prominently during the 2017 influenza season (35.7%). qRT-PCR testing found evidence of influenza in 1.5% of 546 patients, with all positives among STEMI cases. Frequencies of CRI were higher in patients with STEMI and in those with high troponin levels, although these relationships were not statistically significant after adjusting for other variables. The risk of STEMI was significantly greater during influenza seasons in the unadjusted analysis (relative risk: 1.09, 95% confidence interval [CI]: 1.02-1.18), however, this relationship was not significant in the adjusted analysis (adjusted relative risk: 1.03, 95% CI: 0.91-1.16). In Bangladesh, many AMI patients had a recent respiratory illness history, with some showing evidence of influenza. However, these illnesses showed no significant relationship to AMI severity. Further research is needed to understand these relationships better and to investigate the potential benefits of infection control measures and influenza vaccinations in reducing AMI incidence.

Influenza virus circulation and vaccine effectiveness during June 2021–May 2023 in Thailand

Thai Ministry of Public Health recommends influenza vaccination for certain risk groups. We evaluated 2023 Southern Hemisphere influenza vaccine effectiveness against medically attended influenza using surveillance data from nine Thai hospitals and a test-negative design. During June 2022–May 2023, influenza vaccine provided moderate protection against seeking care for influenza illness (adjusted vaccine effectiveness 51%; 95% confidence interval 28–67). Understanding vaccine effectiveness can help guide future antigen selection and support clinicians to make a strong influenza vaccine recommendation to patients.

Influenza Infection and Acute Myocardial Infarction

BackgroundAcute respiratory infections can trigger acute myocardial infarction. We aimed to quantify the association between laboratory-confirmed influenza infection and acute myocardial infarction, particularly in patients with and without known coronary artery disease.MethodsThis observational, registry-based, self-controlled case series study evaluated the association between laboratory-confirmed influenza infection and occurrence of acute myocardial infarction. Laboratory records on respiratory virus polymerase chain reaction (PCR) testing from 16 laboratories across the Netherlands were linked to national mortality, hospitalization, medication, and administrative registries. Influenza infection was defined as a positive PCR test result. Acute myocardial infarction was defined as a registered diagnostic code for either acute myocardial infarction hospitalization or death. Using a self-controlled case series method, we then compared the incidence of acute myocardial infarction during the risk period (days 1 to 7 after influenza infection) versus the control period (1 year before and 51 weeks after the risk period).ResultsBetween 2008 and 2019, we identified 158,777 PCR tests for influenza in the study population; 26,221 were positive for influenza, constituting 23,405 unique influenza illness episodes. A total of 406 episodes were identified with acute myocardial infarction occurring within 1 year before and 1 year after confirmed influenza infection and were included in analysis. Twenty-five cases of acute myocardial infarction occurred during the risk period versus 394 during the control period. The adjusted relative incidence of acute myocardial infarction during the risk period compared with the control period was 6.16 (95% confidence interval [CI], 4.11 to 9.24). The relative incidence of acute myocardial infarction in individuals without prior hospitalization for coronary artery disease was 16.60 (95% CI, 10.45 to 26.37) compared with 1.43 (95% CI, 0.53 to 3.84) for those with prior admission for coronary artery disease.ConclusionsInfluenza infection was associated with an increased risk of acute myocardial infarction, especially in individuals without a prior hospitalization for coronary artery disease. (Funded by the Dutch Research Council [NWO].)

Changes in primary care visits for respiratory illness during the COVID-19 pandemic: a multinational study by the International Consortium of Primary Care Big Data Researchers (INTRePID).

The majority of patients with respiratory illness are seen in primary care settings. Given COVID-19 is predominantly a respiratory illness, the INTernational ConsoRtium of Primary Care BIg Data Researchers (INTRePID), assessed the pandemic impact on primary care visits for respiratory illnesses. Definitions for respiratory illness types were agreed on collectively. Monthly visit counts with diagnosis were shared centrally for analysis. Primary care settings in Argentina, Australia, Canada, China, Norway, Peru, Singapore, Sweden and the United States. Over 38 million patients seen in primary care settings in INTRePID countries before and during the pandemic, from January 1st, 2018, to December 31st, 2021. Relative change in the monthly mean number of visits before and after the onset of the pandemic for acute infectious respiratory disease visits including influenza, upper and lower respiratory tract infections and chronic respiratory disease visits including asthma, chronic obstructive pulmonary disease, respiratory allergies, and other respiratory diseases. INTRePID countries reported a marked decrease in the average monthly visits for respiratory illness. Changes in visits varied from -10.9% [95% confidence interval (CI): -33.1 to +11.3%] in Norway to -79.9% (95% CI: -86.4% to -73.4%) in China for acute infectious respiratory disease visits and - 2.1% (95% CI: -12.1 to +7.8%) in Peru to -59.9% (95% CI: -68.6% to -51.3%) in China for chronic respiratory illness visits. While seasonal variation in allergic respiratory illness continued during the pandemic, there was essentially no spike in influenza illness during the first 2 years of the pandemic. The COVID-19 pandemic had a major impact on primary care visits for respiratory presentations. Primary care continued to provide services for respiratory illness, although there was a decrease in infectious illness during the COVID pandemic. Understanding the role of primary care may provide valuable information for COVID-19 recovery efforts and planning for future global emergencies.

Optimization of timing for maternal immunization to protect newborns from influenza infection

Objectives The primary objective of this systematic review was to identify the optimal timing for immunizing pregnant women to confer the most protection by reducing the incidence of laboratory-confirmed influenza or influenza-like illness in infants less than 6 months of age. Currently, there are gaps in research regarding the timing of administration during the gestational period to provide maximum immunogenicity to the infant. The research question being addressed is: ‘When considering immunization of pregnant mothers with the influenza vaccine, implementing a vaccination program during which trimester in pregnancy would optimize benefits for infants less than 6 months of age in terms of the incidence of laboratory-confirmed influenza and influenza-like illness?’ Design Systematic review/Meta-analysis Methods Randomized controlled trials (RCT’s) and observational studies comparing health outcomes of infants and children up to 6 months of age born to women who received inactivated influenza vaccine during pregnancy with mothers who did not receive the vaccine or received a control vaccine. The primary outcome was laboratory-confirmed influenza infection in infants. Secondary outcome measures included influenza –like illness diagnosed by a clinician and acute respiratory illness. Results 7 studies were included: 2 primary RCT’s and 5 observational studies (prospective and retrospective cohort studies).5 of the 7 studies were suitable to be included in the quantitative synthesis part and and were compared. Forrest plot analysis revealed that vaccinating pregnant mothers in the second and third trimester when compared with any trimester (1,2 and 3) (OR 0.18 vs. 0.65) conferred less protection, promoting vaccination in the first trimester. Conclusions Vaccinating pregnant mothers in the first trimester conferred greater protection to infants than any other trimester.

Repeated vaccination does not appear to significantly weaken the protective effect of influenza vaccine in the elderly: A test-negative case-control study in China

BackgroundThe impact of repeated influenza vaccination on vaccine effectiveness has been a topic of debate. Conducting more multinational, multicenter studies in different influenza seasons is crucial for a better understanding of this issue. There is a lack of comprehensive related research reports in China. MethodsUsing the Regional Health Information Platform, we conducted a test-negative case-control study to evaluate the impact of repeated vaccination on the prevention of laboratory-confirmed influenza in individuals aged 60 and above in Ningbo during four influenza seasons from 2018–19 to 2021–22. Influenza-positive cases and negative controls were matched in a 1:1 ratio based on the visiting hospital and the date of influenza testing. Propensity score adjustment and multivariable logistic regression were used to estimate risk and address confounding effects. ResultsDuring the study period, a total of 30,630 elderly patients underwent influenza virus nucleic acid or antigen testing. After exclusions, we included 1976 cases of influenza-positive and 1976 cases of influenza-negative controls. Multivariable logistic regression analysis revealed that individuals receiving the vaccine in two consecutive seasons did not exhibit a significantly increased risk of influenza illness compared to those receiving the vaccine only in the current season (adjusted odds ratio: 1.22, 95% confidence interval: 0.94–1.58). However, the risk of influenza illness was found to be elevated in individuals who received the vaccine only in the previous season (adjusted odds ratio: 1.56, 95% confidence interval: 1.15–2.10) and even further elevated in those who had not received the vaccine in either of the consecutive two seasons (adjusted odds ratio: 3.39, 95% confidence interval: 2.80–4.09). ConclusionsRegardless of the vaccination history in the previous season, receiving the current season influenza vaccine is the best choice for the elderly population. Our study supports the initiative to vaccinate elderly individuals against influenza annually.