Influenza Vaccine Uptake in the United States before and during the COVID-19 Pandemic

Influenza Vaccination Coverage in Children: How Has COVID-19 Influenced It? A Review of Five Seasons (2018-2023) in Central Catalonia, Spain

Influenza vaccination is the main method of preventing influenza. Vaccination is recommended for certain individuals with diseases that could cause complications in the case of flu infection. The objective of this retrospective observational study was to examine influenza vaccination coverage in patients with risk factors, to describe the characteristics of those vaccinated and to study the influence of COVID-19. The study population was children under 14 years old with risk factors between 2018/19 and 2022/23 in Central Catalonia, sourced through the electronic database of the Catalan Institute of Health. The association of influenza vaccination data with sociodemographic data and risk factors was performed by bivariate and multivariate analysis. A total of 13,137 children were studied. Of those, 4623 had received the influenza vaccine in at least one season. The average influenza vaccination rate was 28.8%. The statistically significant factors associated with vaccination were age and having certain risk factors: asthma, diabetes, haemoglobinopathies and clotting disorders. In all seasons, the immigrant population was vaccinated more than the native population p < 0.05, except for the COVID-19 season (2020/21), where no differences were observed. Of those vaccinated, 7.1% had been vaccinated for 5 consecutive years. Influenza vaccination coverage in the paediatric age group was low. Vaccination promotion measures must be implemented. COVID-19 meant an increase in vaccination of the native population to the same level as that of the immigrant population.

Outcomes of COVID-19 and Influenza in Cerebral Palsy Patients Hospitalized in the United States: Comparative Study of a Nationwide Database

Patients with cerebral palsy (CP) are particularly vulnerable to respiratory infections, yet comparative outcomes between COVID-19 and influenza in this population remain underexplored. Using the National Inpatient Sample from 2020-2021, we performed a retrospective analysis of hospital data for adults with CP diagnosed with either COVID-19 or influenza. The study aimed to compare the outcomes of these infections to provide insights into their impact on this vulnerable population. We assessed in-hospital mortality, complications, length of stay (LOS), hospitalization costs, and discharge dispositions. Multivariable logistic regression and propensity score matching were used to adjust for confounders, enhancing the analytical rigor of our study. The study cohort comprised 12,025 patients-10,560 with COVID-19 and 1465 with influenza. COVID-19 patients with CP had a higher in-hospital mortality rate (10.8% vs. 3.1%, p = 0.001), with an adjusted odds ratio of 3.2 (95% CI: 1.6-6.4). They also experienced an extended LOS by an average of 2.7 days. COVID-19 substantially increases the health burden for hospitalized CP patients compared to influenza, as evidenced by higher mortality rates, longer hospital stays, and increased costs. These findings highlight the urgent need for tailored strategies to effectively manage and reduce the impact of COVID-19 on this high-risk group.

Influenza vaccination patterns among at-risk patients during the Covid-19 pandemic-a retrospective cross-sectional study based on claims data

PURPOSE

The Covid-19 pandemic may have encouraged at-risk patients to get vaccinated against influenza for the first time. As previous vaccinations are known predictors for further vaccinations, knowledge about individual vaccination patterns, especially in first time vaccinated patients, is of great interest. The aim of this study was to determine influenza vaccination uptake rate (VUR), individual vaccination patterns and factors associated with vaccination uptake among at-risk patients.

METHODS

The study design was retrospective cross-sectional. Based on claims data, VUR was determined for four influenza seasons (2018/2019-2021/2022). In a cohort subgroup, with data available for all seasons, VUR, vaccination patterns and factors associated with uptake were determined. At-risk patients were people aged ≥ 65 and adult patients with chronic diseases.

RESULTS

We included n = 238,461 patients in the cross-sectional analysis. Overall VUR ranged between 21.8% (2018/2019) and 29.1% (2020/2021). Cohort subgroup consisted of n = 138,526 patients. Within the cohort, 56% were never vaccinated and 11% were vaccinated in all seasons. 14.3% of previously unvaccinated patients were vaccinated for the first time in the first pandemic season (2020/2021 season). The strongest predictor for vaccination was history of vaccinations in all previous seasons (OR 56.20, 95%CI 53.62-58.90, p < 0.001).

CONCLUSION

Influenza VUR increased during the Covid-19 pandemic, but only a minority of previously eligible but unvaccinated at-risk patients were vaccinated for the first time in the first pandemic season. Previous vaccinations are predictors for subsequent vaccinations and health care professionals should actively address at-risk patients' vaccination history in order to recommend vaccination in future seasons.

Seasonal variations and social disparities in asthma hospitalizations and outcomes

OBJECTIVE

Exposure to asthma exacerbating triggers may be dependent on the season and an individual's social factors and subsequent means to avoid triggers. We assessed for seasonal variations and differential outcomes based on race and income in admissions for asthma in a United States nationwide assessment.

METHODS

This retrospective study assessed adult hospitalizations for asthma 2016-2019 using the National Inpatient Sample. Hospitalizations were categorized by season: winter (December-February), spring (March-May), summer (June-August), fall (September-November). Multivariable linear and logistic regression were used to assess associations between season, race, income quartile (determined by the median income within a patient's ZIP code), and outcomes.

RESULTS

The study included 423,140 admissions with a mean age of 51 years, and 73% of the cohort being female and 56% non-white. Admissions peaked during winter (124, 145) and were lowest in summer (80,525). Intubation rates were increased in summer compared to winter (2.73 vs 1.93%, aOR = 1.19, 95% CI: 1.04-1.37) as were rates of noninvasive positive pressure ventilation (NIPPV) (7.92 vs 7.06%, aOR = 1.08, 95% CI: 1.00-1.17). Compared to white patients, intubation (2.53 vs 1.87%, absolute difference 0.66%, aOR = 1.14, 95% CI: 1.02-1.29) and NIPPV (9.95 vs 5.45%, absolute difference 4.5%, aOR = 1.69, 95% CI: 1.57-1.82) were increased in Black patients. No significant associations between income and clinical outcomes were found.

CONCLUSIONS

Asthma admission peak during winter, while summer admissions and non-white race are associated with higher rates of NIPPV and intubation. Public health initiatives and strategically timed outpatient visits could combat seasonal variation and social disparities in asthma outcomes.

Comparison of COVID-19 and Influenza-Related Outcomes in the United States during Fall-Winter 2022-2023: A Cross-Sectional Retrospective Study

Influenza and COVID-19 contribute significantly to the infectious disease burden during the respiratory season, but their relative burden remains unknown. This study characterizes the frequency and severity of medically attended COVID-19 and influenza during the peak of the 2022-2023 influenza season in the pediatric, adult, and older adult populations and characterizes the prevalence of underlying conditions among patients hospitalized with COVID-19. This cross-sectional analysis included individuals in the Veradigm EHR Database linked to Komodo claims data with a medical encounter between 1 October 2022 and 31 March 2023 (study period). Patients with medical encounters were identified with a diagnosis of COVID-19 or influenza during the study period and stratified based on the highest level of care received with that diagnosis. Among 23,526,196 individuals, there were more COVID-19-related medical encounters than influenza-related encounters, overall and by outcome. Hospitalizations with COVID-19 were more common than hospitalizations with influenza overall (incidence ratio = 4.6) and in all age groups. Nearly all adults hospitalized with COVID-19 had at least one underlying medical condition, but 37.1% of 0-5-year-olds and 25.0% of 6-17-year-olds had no underlying medical conditions. COVID-19 was associated greater burden than influenza during the peak of the 2022-2023 influenza season.

Trends in influenza vaccine uptake before and during the COVID-19 pandemic in the USA

OBJECTIVES

To investigate trends of influenza vaccine uptake before and during the COVID-19 pandemic in the USA and explore the associated factors.

STUDY DESIGN

This was a cross-sectional study.

METHODS

Using self-reported data from the National Health Interview Survey during 2014-2021 (response rates ranging from 50.7 to 70.1%), we estimated influenza vaccine uptake. Log-binomial regression models were used to test uptake changes with adjustment for and stratification by demographic and health factors.

RESULTS

We included 58,249 children (mean age: 8.7 years; male: 51.1%) and 205,034 adults (mean age: 47.6 years; male: 48.2%). The prevalence ratio (PR) of uptake change comparing the intra- (2020-2021) to the pre-COVID-19 period (2014-2019) was 0.72 among children, with a 10.7% reduction. Uptake changes were found across subgroups, with higher reduction among those aged 0-2 years, non-Hispanic Black and Hispanic ethnicity, from South and West regions, and with lower household income. For adults, uptake increased before and during COVID-19 (PR = 1.15, 95% confidence interval [CI]: 1.12-1.18) but a 2.3% reduction was found among healthcare personnel (PR = 0.95, 95% CI: 0.90-0.997).

CONCLUSIONS

Influenza vaccination decreased during the COVID-19 pandemic among children and healthcare personnel. Structure inequality to influenza vaccination warrants measures to improve vaccine uptake among vulnerable groups.

Trends in Influenza Vaccination Rates among a Medicaid Population from 2016 to 2021

Seasonal influenza is a leading cause of death in the U.S., causing significant morbidity, mortality, and economic burden. Despite the proven efficacy of vaccinations, rates remain notably low, especially among Medicaid enrollees. Leveraging Medicaid claims data, this study characterizes influenza vaccination rates among Medicaid enrollees and aims to elucidate factors influencing vaccine uptake, providing insights that might also be applicable to other vaccine-preventable diseases, including COVID-19. This study used Medicaid claims data from nine U.S. states (2016-2021], encompassing three types of claims: fee-for-service, major Medicaid managed care plan, and combined. We included Medicaid enrollees who had an in-person healthcare encounter during an influenza season in this period, excluding those under 6 months of age, over 65 years, or having telehealth-only encounters. Vaccination was the primary outcome, with secondary outcomes involving in-person healthcare encounters. Chi-square tests, multivariable logistic regression, and Fisher's exact test were utilized for statistical analysis. A total of 20,868,910 enrollees with at least one healthcare encounter in at least one influenza season were included in the study population between 2016 and 2021. Overall, 15% (N = 3,050,471) of enrollees received an influenza vaccine between 2016 and 2021. During peri-COVID periods, there was an increase in vaccination rates among enrollees compared to pre-COVID periods, from 14% to 16%. Children had the highest influenza vaccination rates among all age groups at 29%, whereas only 17% were of 5-17 years, and 10% were of the 18-64 years were vaccinated. We observed differences in the likelihood of receiving the influenza vaccine among enrollees based on their health conditions and medical encounters. In a study of Medicaid enrollees across nine states, 15% received an influenza vaccine from July 2016 to June 2021. Vaccination rates rose annually, peaking during peri-COVID seasons. The highest uptake was among children (6 months-4 years), and the lowest was in adults (18-64 years). Female gender, urban residency, and Medicaid-managed care affiliation positively influenced uptake. However, mental health and substance abuse disorders decreased the likelihood. This study, reliant on Medicaid claims data, underscores the need for outreach services.

Global burden of influenza lower respiratory tract infections in older people from 1990 to 2019

BACKGROUND

Infections with influenza viruses cause severe illness, substantial number of hospitalization and death, especially in older adults. However, few studies have focused on the burden of influenza lower respiratory tract infections (LRTIs) solely in older adults, particularly in low-resource settings.

AIMS

We aimed to estimate the mortality and DALYs of influenza LRTIs for people aged 55 years and older in 204 countries and territories from 1990 to 2019.

METHODS

The Global Burden of Disease (GBD) 2019 study was used to obtain data on mortality and DALYs of influenza LRTIs at the global, regional, and country levels.

RESULTS

In 2019, the global rates for mortality and DALYs of influenza LRTIs were 6.46 per 100,000 [95% uncertainty interval (UI): 2.37-12.62] and 97.39 per 100,000 (95% UI: 34.70-187.03). Although the rates for mortality and DALYs in people aged 55 years and older decreased from 1990 to 2019, the absolute numbers for both increased by 85.84% and 66.56%, respectively. Both the absolute numbers and rates of deaths and DALYs of influenza LRTIs were higher in male than in female in all age groups. Although low-socio-demographic index (SDI) regions experienced the largest declines for the rates of mortality and DALYs of influenza LRTIs over the past three decades, they still had the highest rates for mortality and DALYs in all age groups. Moreover, the absolute numbers and rates of deaths and DALYs of influenza LRTIs showed an increasing trend with age, reaching the peak in the people over 85 years old.

DISCUSSION

Burden of influenza LRTIs in older adults is still high and could continue to grow along with global aging.

CONCLUSION

Efforts to improve vaccination for influenza are needed for preparedness of another influenza pandemic, especially in low-SDI regions.

Comparing demographics, clinical characteristics, and hospital outcomes by vaccine uptake status: A single-institution cross-sectional study

Vaccination against Coronavirus disease 2019 (COVID-19) has been the cornerstone of reducing morbidity and mortality of this disease, as it has been shown to decrease the risk of viral transmission, severity of disease, hospitalization, and intubation. However, true understanding of its impact is skewed by heterogeneous vaccine administration due to lack of equitable access, vaccine hesitancy, and varying social determinants of health. Therefore, this study aims to identify groups that are less likely to be vaccinated and understand whether the resultant differences in vaccination rates affect morbidity and mortality in socially marginalized COVID-19 patients. A retrospective cohort analysis was performed on a randomized and stratified population of 939 COVID-19 patients from January 2021 to December 2021. Bivariate analysis and logistic regression were used to assess demographic and clinical characteristic trends in unvaccinated, partially vaccinated, and fully vaccinated groups. No one age (P = .21), gender (P = .9), race (P = .12), ethnicity (P = .09), or health insurance status (P = .13) group was more vaccinated than the other. Similarly, no subgroup was at increased odds of intubation (P = .08) or death. However, patients with all categories of comorbidities including cardiopulmonary disease (P = <.001, effect size .17), renal disease (P = <.001, effect size 0.138), metabolic disease (P = .04), and immunocompromised (P = .01) states were found to have significantly higher vaccination rates. Our study also shows that full vaccination protects against mortality and decreases the odds of intubation by 55% (adjusted odds ratio = 0.453, P value = .015) compared to no vaccination or partial vaccination. Findings from this study show an encouraging trend that sicker patients had higher rates of vaccination against COVID-19. This trend highlights the need for further identification of motivators that may be applied to vaccine-hesitant populations, which can help guide population-level policy, increase vaccination campaign yield, and reach for health equity.

Lessons learned from the COVID-19 pandemic for improved influenza control

The World Health Organization noted that COVID-19 vaccination programmes could be leveraged to deliver influenza vaccination. In 2008, the International Federation of Pharmaceutical Manufacturers and Associations' (IFPMA) Influenza Vaccine Supply International Task Force (IVS) developed a survey method using the number of influenza vaccine doses distributed globally to estimate vaccination coverage rates. Seven hundred and ninety-seven million doses were distributed in 2021, representing a 205% increase over the 262 million doses distributed in 2004, exceeding the number of doses distributed during and after the 2009-2010 influenza pandemic. The most obvious explanation for the global increase is the enabling of critical elements of the vaccine ecosystem by decision-makers during the COVID-19 pandemic to reinforce implementation of influenza vaccination programs. Most of the improvements in performance of influenza programs during the COVID-19 pandemic can be classified in four categories: 1) promoting vaccination using tailored approaches for specific populations; 2) improving convenient access to influenza vaccines in COVID-safe settings; 3) improving reimbursement of seasonal influenza vaccination for priority groups; 4) maintaining the timing of vaccination to the autumn. In spite of the increase in rates of seasonal influenza vaccines distributed during the COVID-19 pandemic, globally, the rate of influenza dose distribution is sub-optimal, and a considerable proportion of the influenza infections remains preventable. To sustain the benefits from increased uptake of influenza vaccines, governments need to sustain the efforts made during the COVID-19 pandemic, and a number of global policy endeavours should be undertaken, including developing a clear global roadmap for achieving influenza control objectives, adopted by a WHA resolution, in line with the strategic objective 3 of the Global Influenza Strategy 2030, embedded in the Immunization Agenda 2030 (IA2030).

Effect of Primary Care Center Characteristics, Healthcare Worker Vaccination Status and Patient Economic Setting on Patient Influenza Vaccination Coverage Rates

BACKGROUND

Reaching the public health organizations targets of influenza vaccination in at-risk patient groups remains a challenge worldwide. Recognizing the relationship between the healthcare system characteristics and the economic environment of the population with vaccination uptake can be of great importance to improve.

METHODS

Several characteristics were correlated in this retrospective ecological study with data from 6.8 million citizens, 15,812 healthcare workers across 258 primary care health centers, and average income by area of the care center in Spain.

RESULTS

No correlation between HCW vaccination status and patient vaccination was found. A weak negative significant correlation between the size of the population the care center covers and their vaccination status did exist (6 mo.-59 yr., r = 0.19, p = 0.002; 60-64 yr., r = 0.23, p < 0.001; ≥65 yr., r = 0.23, p ≥ 0.001). The primary care centers with fewer HCWs had better uptake in the at-risk groups in the age groups of 60-64 yr. (r = 0.20, p = 0.002) and ≥65 (r = 0.023, p ≥ 0.001). A negative correlation was found regarding workload in the 6 mo.-59 yr. age group (r = 0.18, p = 0.004), which showed the at-risk groups that lived in the most economically deprived areas were more likely to be vaccinated.

CONCLUSIONS

This study reveals that the confounding variables that determine influenza vaccination in a population and in HCWs are complex. Future influenza campaigns should address these especially considering the possibility of combining influenza and SARS-CoV-2 vaccines each year.

Epidemiology of Respiratory Infections during the COVID-19 Pandemic

To face the COVID-19 outbreak, a wide range of non-pharmaceutical interventions (NPIs) aimed at limiting the spread of the virus in communities, such as mask-wearing, hand hygiene, social distancing, travel restrictions, and school closures, were introduced in most countries. Thereafter, a significant reduction of new asymptomatic and symptomatic COVID-19 cases occurred, although there were differences between countries according to the type and duration of the NPIs. In addition, the COVID-19 pandemic has been accompanied by significant variations in the global incidence of diseases due to the most common non-SARS-CoV-2 respiratory viruses and some bacteria. In this narrative review, the epidemiology of the most common non-SARS-CoV-2 respiratory infections during the COVID-19 pandemic is detailed. Moreover, factors that could have had a role in modifying the traditional circulation of respiratory pathogens are discussed. A literature analysis shows that NPIs were the most important cause of the general reduction in the incidence of influenza and respiratory syncytial virus infection in the first year of the pandemic, although the different sensitivity of each virus to NPIs, the type and duration of measures used, as well as the interference among viruses may have played a role in modulating viral circulation. Reasons for the increase in the incidences of Streptococcus pneumoniae and group A Streptococcus infections seem strictly linked to immunity debt and the role played by NPIs in reducing viral infections and limiting bacterial superimposed infections. These results highlight the importance of NPIs during pandemics, the need to monitor the circulation of infectious agents that cause diseases similar to those caused by pandemic agents, and the need to make efforts to improve coverage with available vaccines.

Trends in Hospitalization and Mortality for Influenza and Other Respiratory Viruses during the COVID-19 Pandemic in the United States

Seasonal epidemics of respiratory viruses, respiratory syncytial virus (RSV), influenza viruses, parainfluenza viruses (PIVs), and human metapneumovirus (MPV) are associated with a significant healthcare burden secondary to hundreds of thousands of hospitalizations every year in the United States (US) alone. Preventive measures implemented to reduce the spread of SARS-CoV-2 (COVID-19 infection), including facemasks, hand hygiene, stay-at-home orders, and closure of schools and local/national borders may have impacted the transmission of these respiratory viruses. In this study, we looked at the hospitalization and mortality trends for various respiratory viral infections from January 2017 to December 2020. We found a strong reduction in all viral respiratory infections, with the lowest admission rates and mortality in the last season (2020) compared to the corresponding months from the past three years (2017-2019). This study highlights the importance of public health interventions implemented during the COVID-19 pandemic, which had far-reaching public health benefits. Appropriate and timely use of these measures may help to reduce the severity of future seasonal respiratory viral outbreaks as well as their burden on already strained healthcare systems.