The adult vaccination landscape in the United States during the Affordable Care Act era: Results from a large retrospective database analysis

BackgroundEarly provisions of the Affordable Care Act (ACA) reduced financial barriers to preventive care, including routinely recommended vaccines; however, vaccination coverage remains suboptimal. This study examined characteristics of routine adult vaccinations and potential missed opportunities for vaccinations through the lens of healthcare resource utilization among adults in the ACA era.MethodsThis was a retrospective analysis of healthcare claims from the Truven Health MarketScan Commercial Claims and Encounters (CCAE), Medicare Supplemental (MS), and Multi-State Medicaid databases among adults aged 19 years or older. Influenza, Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis), herpes zoster (HZ), and pneumococcal vaccinations were identified between 2011 and 2016. Potential missed opportunities were defined as well-visits at which individuals were age-eligible for vaccination but did not receive it, assessed during recommended windows for each vaccine. Missed encounters were defined as having no well-visits. Multivariable logistic regression was used to identify factors associated with vaccination and potential missed opportunities.ResultsFamily/internal medicine and unknown/other providers administered most influenza, Tdap, and pneumococcal vaccinations, for the CCAE/MS and Medicaid cohorts, respectively. HZ vaccinations were primarily administered through pharmacies. The proportion of vaccination events increased in the pharmacy setting between 2011 and 2016. Having preventive care visits, non-well-visits, and receiving most care from a family/internal medicine practitioner were associated with increased odds of vaccination. Missed encounters were common in Medicaid enrollees. Potential missed opportunities were more prevalent in the CCAE/MS cohort than among Medicaid enrollees. Having non-well-visits was associated with a reduced likelihood of having a missed opportunity.ConclusionSince the ACA implementation, preventive care among adults was sporadic. Many adults had limited opportunities for vaccination. The large prevalence of missed opportunities suggests vaccination uptake could be improved. Better support for vaccination or referrals for providers who may not traditionally vaccinate could improve vaccine uptake.     

Survey of influenza vaccine knowledge,attitudes, and beliefs among pregnant women in the 2016–17 season

ObjectivesInfluenza vaccination coverage among pregnant women in the United States is suboptimal. We surveyed women who were pregnant during the 2016–17 influenza season to assess knowledge and attitudes regarding influenza vaccination.MethodsWe identified and sampled pregnant women to include approximately equal numbers of vaccinated and unvaccinated women from strata defined by vaccination status and trimester from four integrated health systems in the Vaccine Safety Datalink (VSD). Potential participants were contacted via mail and telephone to complete a standardized survey. Characteristics and responses of women vaccinated and unvaccinated during pregnancy were compared.ResultsThe survey was completed by 510 (48%) of 1062 contacted women; 500 were included in the analysis. Vaccine receipt while pregnant was associated with primigravida status (p = 0.02), college degree (p = 0.01), employment in health care (p < 0.01), and history of routine annual influenza vaccination (p < 0.01). Among 330 vaccinated women, the primary reasons for vaccination included protection of self and baby from influenza (n = 233, 71%), and medical professional recommendation (n = 46, 14%). Multiple reasons were given for nonvaccination, but concern about ‘negative effects’ was cited most often (n = 44, 29%). Vaccinated women were significantly more likely to believe that influenza vaccines are safe and effective, and to recognize the potential for harm from influenza infection. Nearly all women reported receiving at least one influenza vaccination recommendation from a healthcare provider.ConclusionsVaccinated pregnant women were more likely to receive routine annual influenza vaccine compared to those not vaccinated. Recommendations by obstetric providers should be supplemented with efforts to encourage women of childbearing age to receive annual vaccination.     

Body mass index and vaccine responses following influenza vaccination during pregnancy

Background and AimsInfluenza vaccination is recommended by the World Health Organisation for pregnant women, offering the dual benefit of protecting pregnant women and their newborn infants against influenza infection. Various factors can influence vaccine immunogenicity, with obesity being one factor implicated in varied responses. This study aimed to investigate the impact of body mass index (BMI) on vaccine responses following influenza vaccination during pregnancy.MethodsPregnant women attending the Women’s and Children’s Hospital in South Australia during 2014–2016 were invited to participate. Participant’s clinical and demographic factors were recorded prior to administration of licensed seasonal influenza vaccination. Blood samples were collected before and one month post-vaccination to measure antibody responses by haemagglutination inhibition (HI) assay. Seroprotection was defined as a post-vaccination HI titre ≥ 1:40. Regression models assessed associations with failure to achieve seroprotective antibodies to H1, H3, and B influenza strains.ResultsA total of 96 women were enrolled in the study at a median gestation of 22 weeks with a BMI range of 18–49 kg/m². Paired sera samples were available for 90/96 (94%). Most pregnant women (72/90, 80%) demonstrated seroprotective antibody titres to all three influenza vaccine antigens (A(H1N1)pdm09, A(H3N2), B/Yamagata) following vaccination. Compared with women with BMI < 30 kg/m², those with high BMI were less likely to fail to achieve seroprotective antibodies, however this was not statistically significant (RR 0.42, 95% CI 0.11–1.68; p = 0.22). A greater proportion of women vaccinated during their second (47/53, 93%) or third trimester (18/25, 72%) demonstrated seroprotection to all three vaccine antigens following vaccination compared with women vaccinated during their first trimester (7/12, 58%).ConclusionHigh BMI did not impair seroprotection levels following influenza vaccination in pregnant women. Gestation at vaccination may be an important consideration for optimising vaccine protection for pregnant women and their newborns. Further assessment of first trimester influenza vaccine responses is warranted.     

Repeated exposure to an MF-59 adjuvanted quadrivalent subunit influenza vaccine (aQIV) in children: Results of two revaccination studies

BackgroundPediatric adjuvanted seasonal influenza vaccines induce higher immune responses and have the potential to confer better protection against influenza among young vaccine-naïve children. Limited data describe benefits and risks of repeated administration of adjuvanted influenza vaccines in children. Two revaccination studies assess the safety and immunogenicity of repeated exposure to an MF59-adjuvanted quadrivalent influenza vaccine (aQIV; Fluad®) compared to routine non-adjuvanted quadrivalent influenza vaccine (QIV).MethodsChildren previously enrolled in the parent study, who received vaccination with aQIV or nonadjuvanted influenza vaccine (TIV or QIV), were recruited in Season 1 (n = 607) or Season 2 (n = 1601) of the extension trials. Season 1 participants remained in their original randomization groups (aQIV-aQIV or TIV-QIV); Season 2 subjects were re-randomized to either vaccine, resulting in four groups (aQIV-aQIV, aQIV-QIV, QIV-aQIV, or QIV-QIV). All subjects received a single-dose vaccination. Blood samples were taken for immunogenicity assessment prior to vaccination and 21 and 180 days after vaccination. Reactogenicity (Days 1–7) and safety were assessed in all subjects.ResultsHemagglutination inhibition (HI) geometric mean titer (GMT) ratios demonstrated superiority of aQIV revaccination over QIV revaccination for all strains in Season 1 and for A/H1N1, B/Yamagata, and B/Victoria in Season 2. Higher HI titers against heterologous influenza strains were observed after aQIV vaccination during both seasons. Mild to moderate severity and short duration reactogenicity was more common in the aQIV than QIV groups, but the overall safety profiles were similar to the parent study.ConclusionThe safety and immunogenicity results from this study demonstrate benefit of aQIV for both priming and revaccination of children aged 12 months to 7 years.     

Vaccine exposure during pregnancy among privately and publicly insured women in the United States, 2016–2018

BackgroundVaccine use during pregnancy affects maternal and infant health. Many women do not receive vaccines recommended during pregnancy; conversely, inadvertent exposure to vaccines contraindicated or not recommended during pregnancy may occur. We assessed exposure to two recommended vaccines and two vaccines not recommended during pregnancy among privately and Medicaid-insured women in the United States.MethodsThis study includes a retrospective cohort of pregnancies in women aged 12–55 years resulting in live birth, spontaneous abortion, or stillbirth identified in the IBM® MarketScan® Commercial, Blue Health Intelligence® (BHI®) Commercial, and IBM MarketScan Multi-State Medicaid Databases from August 1, 2016, to December 31, 2018. Gestational age at vaccination was determined using a validated algorithm. We examined vaccines (1) recommended by the Centers for Disease Control and Prevention Advisory Committee on Immunization Practices (ACIP) (tetanus, diphtheria, and acellular pertussis [Tdap]; inactivated influenza) and (2) not recommended (human papillomavirus [HPV]) or contraindicated (measles, mumps, and rubella [MMR]).ResultsWe identified 496,771 (MarketScan Commercial), 858,961 (BHI), and 289,573 (MarketScan Medicaid) pregnancies (approximately 75% aged 20–34 years). Across these three databases, 52.1%, 50.3%, and 31.3% of pregnancies, respectively, received Tdap, most often at a gestational age of 28 weeks, and influenza vaccination occurred in 32.1%, 30.8%, and 18.0% of pregnancies, respectively. HPV vaccination occurred in < 0.2% of pregnancies, mostly in the first trimester among women aged 12–19 years, and MMR was administered in < 0.1% of pregnancies. Use of other contraindicated vaccines per ACIP (e.g., varicella, live attenuated influenza) was rare.ConclusionMaternal vaccination with ACIP-recommended vaccines was suboptimal among privately and Medicaid-insured patients, with lower vaccination coverage among Medicaid-insured pregnancies than their privately insured counterparts. Inadvertent exposure to contraindicated vaccines during pregnancy was rare. This study evaluated only vaccinations reimbursed among insured populations and may have limited generalizability to uninsured populations.     

Influenza vaccine uptake in the elderly population: Individual and general practitioner’s determinants in Central Italy,Lazio region, 2016–2017 season

BackgroundElderly people are a priority target group for influenza vaccination and their decision to be vaccinated might partly depend on advice received from general practitioners (GP). This study aims to investigate the association between influenza vaccine uptake in the elderly residents in the Lazio region of Italy and the demographic and professional characteristics of their GPs, taking simultaneously into account the elderly’s individual characteristics.MethodsWe used data retrieved from different administrative sources to retrospectively analyse the cohort of 1,255,657 elderly residents aged ≥65 years who were alive and registered in the regional healthcare service at the beginning of the 2016–2017 influenza vaccination campaign (1 Oct. 2016–31 Jan. 2017). We assessed influenza vaccine uptake at the end of the vaccination campaign and evaluated its association with both individual and GP-related characteristics through a multilevel Poisson regression models accounting for clustering at physician level.ResultsOverall, vaccination coverage at the end of vaccination campaign was 50.6%. Elderly residents who were male, older, vaccinated in the previous seasons, living in smaller provinces, and spending more money for specialist medical care showed a significantly increased probability to be vaccinated. Vaccine uptake was also significantly higher in the elderly residents assisted by GPs who got master’s degree more recently, assisted a relatively high proportion of elderly patients, received influenza vaccination, had a computer assistant, and were associated with other physicians.ConclusionsOur results indicate that influenza vaccination coverage in the elderly residents of the Lazio region is still unsatisfactorily low. We identified several determinants of influenza vaccine uptake, related to both individual and GP characteristics. Understanding how GP characteristics affected influenza vaccine uptake in the elderly population might provide insight on GPs’ attitudes and concerns regarding influenza vaccination, allowing the implementation of targeted evidence-based interventions to sensitise GPs and increase vaccination coverage.     

Barriers and activities to implementing or expanding influenza vaccination programs in low- and middle-income countries: A global survey

IntroductionDespite considerable global burden of influenza, few low- and middle-income countries (LMICs) have national influenza vaccination programs. This report provides a systematic assessment of barriers to and activities that support initiating or expanding influenza vaccination programs from the perspective of in-country public health officials.MethodsPublic health officials in LMICs were sent a web-based survey to provide information on barriers and activities to initiating, expanding, or maintaining national influenza vaccination programs. The survey primarily included Likert-scale questions asking respondents to rank barriers and activities in five categories.ResultsOf 109 eligible countries, 62% participated. Barriers to influenza vaccination programs included lack of data on cost-effectiveness of influenza vaccination programs (87%) and on influenza disease burden (84%), competing health priorities (80%), lack of public perceived risk from influenza (79%), need for better risk communication tools (77%), lack of financial support for influenza vaccine programs (75%), a requirement to use only WHO-prequalified vaccines (62%), and young children require two vaccine doses (60%). Activities for advancing influenza vaccination programs included educating healthcare workers (97%) and decision-makers (91%) on the benefits of influenza vaccination, better estimates of influenza disease burden (91%) and cost of influenza vaccination programs (89%), simplifying vaccine introduction by focusing on selected high-risk groups (82%), developing tools to prioritize target populations (80%), improving availability of influenza diagnostic testing (79%), and developing collaborations with neighboring countries for vaccine procurement (74%) and regulatory approval (73%). Responses varied by country region and income status.ConclusionsLocal governments and key international stakeholders can use the results of this survey to improve influenza vaccination programs in LMICs, which is a critical component of global pandemic preparedness for influenza and other pathogens such as coronaviruses. Additionally, strategies to improve global influenza vaccination coverage should be tailored to country income level and geographic location.     

Signals and trends of Guillain–Barré syndrome after the introduction of live-attenuated vaccines for influenza in the US and South Korean adverse event reporting systems

BackgroundWith the advent of live-attenuated, quadrivalent, and cell-cultured vaccines for influenza, there have been discussions on the safety of these vaccines compared to conventional vaccines (such as inactivated, trivalent, and egg-cultured vaccines) because of the development of neurological adverse events (AEs). This study aimed to compare the trends and safety signals in the AE reporting systems of the US and South Korea and, more particularly, to evaluate the association between influenza vaccination and Guillain–Barré syndrome (GBS).MethodsIn total, 400,535 AE reports from the US Vaccine Adverse Event Reporting System (VAERS) and 28,766 AE reports from the Korea Adverse Event Reporting System (KAERS) between 2005 and 2017 were assessed. Disproportionality analysis was performed to detect the safety signals and examine the potential risk of GBS with influenza vaccination using the case/non-case approach.ResultsIn both databases, GBS was the most frequently reported AE following influenza immunization. Using the case/non-case approach, the adjusted reporting odds ratio (ROR) of GBS was 3.57 (95% confidence interval [CI], 3.16–4.03) and 3.09 (95% CI, 0.83–11.45) in the VAERS and KAERS data, respectively. People vaccinated with live-attenuated vaccines reported 2.30 times (95% CI, 1.74–3.05) more cases of GBS than those vaccinated with other types of vaccines.ConclusionsOur analysis of the VAERS and KAERS reports for AEs following immunization (AEFI) for influenza shows the need for cautious monitoring regarding the development of GBS after influenza vaccination, particularly, after live-attenuated vaccination. However, owing to potential reporting bias caused by limited AEFI reports after the introduction of new types of influenza vaccines, further prospective safety studies are needed.     

Association between health insurance coverage and uptake of seasonal influenza vaccine in Brazos County,Texas

BackgroundLack of health insurance may limit access to influenza vaccination, resulting in higher risk of infection.MethodsThe Brazos County Health Department obtained medical records summarizing vaccination and health insurance status of all influenza cases occurring in December 2017 (n = 417). The odds of influenza vaccination were estimated for those with public or private health insurance as compared to uninsured individuals using multivariate logistic regression analysis adjusted for age and race.ResultsHealth insurance coverage among Brazos County residents with influenza was 62.4%. Public and private health insurance was associated with higher odds of influenza vaccination compared to no insurance (aOR: 2.05; 95% CI: 1.00–4.21 and aOR: 1.77; 95% CI: 1.07–2.92, respectively), particularly among adults 18–64 years of age.ConclusionsInfluenza vaccination is strongly associated with health insurance. Expansion of programs that facilitate access to health services or provide free influenza vaccines may improve influenza prevention among the uninsured.     

Cost-effectiveness of introducing an MF59-adjuvanted trivalent influenza vaccine for older adults in Argentina

IntroductionInfluenza surveillance in Argentina reported influenza-like illness at a rate of 3500/100,000, a hospitalization rate of 15.5/100,000, and a death rate of 0.32/100,000 annually in adults aged over 65 years. The high burden of disease may be due to a combination of immunosenescence and the suboptimal clinical effectiveness of conventional, non-adjuvanted influenza vaccines in this age group. There is a clinical need for more effective influenza vaccines in this population. This study evaluated the cost-effectiveness of an MF59®-adjuvanted trivalent influenza vaccine (aTIV) in adults aged over 65 years in Argentina compared with the non-adjuvanted trivalent influenza vaccine (TIV) used under the current national vaccination policy.MethodsA decision tree cost-effectiveness model was developed to estimate the cost-effectiveness of switching from TIV to aTIV in Argentinian older adults. The model compared cost and health benefits of vaccination in one influenza season from the payer perspective. The main predictions included survival, quality-adjusted survival, and costs. Model inputs were sourced from Argentina or internationally where local data was considered inaccurate. Vaccine efficacy assumptions were extracted from recently published, peer-reviewed scientific literature.ResultsSwitching from TIV to aTIV would result in 170 deaths averted and 1310 incremental quality-adjusted life years (QALYs) gained. The incremental cost-effectiveness ratio per QALY was US $2660.59 from the payer perspective. In all sensitivity analyses, aTIV remained highly cost-effective. The probabilistic sensitivity analyses showed a 95% CI per QALY of US $113.74–7721.67.ConclusionIntroducing an adjuvanted influenza vaccine in Argentina is potentially beneficial and cost-effective relative to the currently-used TIV through the reduction of disease burden and utilization of healthcare resources.     

Pneumococcal vaccination in older adults: An initial analysis of social determinants of health and vaccine uptake

ObjectivesTo examine the potential influence of social determinants of health on pneumococcal vaccination in older American adults.MethodsThis study used nationwide, US Medicare claims data from 2013 to 2016 to assess uptake of pneumococcal vaccination among adults in the first year after turning age 65. Patients were followed from the point of being 65 years of age and initially enrolled in traditional fee-for-service Medicare or a Medicare Advantage plan through the subsequent year and observed for pneumococcal vaccination in outpatient clinics and pharmacies. Publicly-available data on select social determinants of health were incorporated and guided by the World Health Organization vaccine hesitancy matrix. Logistic regression determined predictors of vaccination while controlling clinical and demographic characteristics.ResultsA total of 307,488 and 74,995 adults aged 65 years were identified from Medicare Advantage and Medicare fee-for-service claims, respectively, and 21.1% of Medicare Advantage and 38.2% of Medicare fee-for-service patients received a pneumococcal vaccine in the first year after turning 65. Those residing in urban areas had a higher likelihood of pneumococcal vaccination in both the Medicare Advantage (OR: 1.31; 95% CI: 1.267–1.344) and Medicare fee-for-service (OR: 1.53; 95% CI: 1.450–1.615) cohorts. Additionally, residing in areas of higher health literacy or communities with more democratic voters were consistently associated with a higher odds of pneumococcal vaccination regardless of Medicare type. Results also pointed to a synergistic relationship between receiving the influenza vaccine and also being vaccinated against pneumococcal disease.ConclusionSocial determinants of health, including local health literacy, poverty, residing in more liberal areas, and access to information, may be influencing the pneumococcal vaccine-related decisions of older adults. However, additional factors associated with the vaccine hesitancy matrix and more granular data (e.g., zip code-level) are needed to fully determine the impact in this and other vaccines recommended in older adults.     

Impact of prior vaccination on antibody response and influenza-like illness among Australian healthcare workers after influenza vaccination in 2016

BackgroundEpidemiological studies suggest that influenza vaccine effectiveness decreases with repeated administration. We examined antibody responses to influenza vaccination among healthcare workers (HCWs) by prior vaccination history and determined the incidence of influenza infection.MethodsHCWs were vaccinated with the 2016 Southern Hemisphere quadrivalent influenza vaccine. Serum samples were collected pre-vaccination, 21–28 days and 7 months post-vaccination. Influenza antibody titres were measured at each time-point using the haemagglutination inhibition (HI) assay. Immunogenicity was compared by prior vaccination history.ResultsA total of 157 HCWs completed the study. The majority were frequently vaccinated, with only 5 reporting no prior vaccinations since 2011. Rises in titres for all vaccine strains among vaccine-naïve HCWs were significantly greater than rises observed for HCWs who received between 1 and 5 prior vaccinations (p < 0.001, respectively). Post-vaccination GMTs against influenza A but not B strains decreased as the number of prior vaccinations increased from 1 to 5. There was a significant decline in GMTs post-season for both B lineages. Sixty five (41%) HCWs reported at least one influenza-like illness episode, with 6 (4%) identified as influenza positive.ConclusionsVarying serological responses to influenza vaccination were observed among HCWs by prior vaccination history, with vaccine-naïve HCWs demonstrating greater post-vaccination responses against A(H3N2).     

Importance and value of adjuvanted influenza vaccine in the care of older adults from a European perspective – A systematic review of recently published literature on real-world data

BackgroundThere is an urgent need for improved influenza vaccines especially for older adults due to the presence of immunosenescence. It is therefore highly relevant to compare enhanced influenza vaccines with traditional influenza vaccines with respect to their effectiveness.ObjectiveTo compare vaccine efficacy and effectiveness of adjuvanted influenza vaccines (aTIV/aQIV) vs. non-adjuvanted standard-dose (TIV/QIV) and high-dose (TIV-HD/QIV-HD) influenza vaccines regarding influenza-related outcomes in older adults, complementing findings from the European Centre for Disease Prevention and Control (ECDC)’s systematic review of enhanced seasonal influenza vaccines from February 2020.MethodsA systematic literature search was conducted in Embase and MEDLINE to identify randomised controlled trials, observational studies and systematic reviews, published since ECDC’s systematic review (between 7 February 2020 and 6 September 2021). Included studies were appraised with either the Cochrane Risk of Bias tool, ROBINS-I or AMSTAR 2.ResultsEleven analyses from nine real-world evidence (RWE) studies comprising ～53 million participants and assessing the relative vaccine effectiveness (rVE) of aTIV vs. TIV, QIV and/or TIV-HD in adults aged ≥65 years over the 2006/07–2008/09 and 2011/12–2019/20 influenza seasons were identified. Nine analyses found that aTIV was significantly more effective than TIV and QIV in reducing influenza-related outcomes by clinical setting and suspected influenza outbreaks (rVE ranging from 7.5% to 25.6% for aTIV vs. TIV and 7.1% to 36.3% for aTIV vs. QIV). Seven analyses found similar effectiveness of aTIV vs. TIV-HD in reducing influenza-related medical encounters, inpatient stays and hospitalisations/emergency room visits. In three analyses, aTIV was significantly more effective than TIV-HD in reducing influenza-related medical encounters and office visits (rVE ranging from 6.6% to 16.6%). Risk of bias of identified studies was moderate to high.ConclusionsOur study suggests that both adjuvanted and high-dose vaccines are effective alternatives for vaccination programmes in older adults and preferable over conventional standard-dose vaccines.     

Effectiveness of a multimodal intervention to increase vaccination in obstetrics/gynecology settings

ObjectiveTo test the effectiveness of a multimodal intervention in obstetrics/gynecology (ob-gyn) clinics to increase uptake of influenza and tetanus-diphtheria-acellular pertussis (Tdap) vaccines in pregnant women and these vaccines plus human papillomavirus (HPV) vaccine in non-pregnant women.MethodsA cluster randomized controlled trial among 9 private ob-gyn practices in Colorado from 9/2011 to 5/2014. The intervention consisted of: designation of immunization champions, staff/provider trainings, assistance with vaccine purchasing/management, identification of eligible patients, standing order implementation, chart review/feedback, and patient education materials. Control practices continued usual care. Primary outcomes were receipt of influenza and Tdap vaccines among pregnant women and these vaccines plus HPV vaccine among non-pregnant women, comparing a Baseline period (Year 0/Year 1) to Year 2, intervention versus control. With an estimated sample size of 32,590 per arm, there would be >80% power to detect a 10% difference between groups.ResultsIn the Baseline period, 27% of pregnant women in both intervention and control practices received influenza vaccine. In Year 2, 29% of pregnant women in intervention practices received influenza vaccine versus 41% in control practices. In the Baseline period, 18% of pregnant women in intervention practices received Tdap vaccine versus 22% in control practices. Both intervention and control practices increased to 51% in Year 2, representing an increase of 33% for intervention practices and 29% for control practices, consistent with a change in Tdap recommendations. Relatively few HPV, influenza or Tdap vaccines (≤6% of eligible patients) were given to non-pregnant patients in either intervention or control practices at any time during the study.ConclusionIn this cluster randomized trial designed to increase vaccination uptake, both intervention and control practices showed improved vaccination of pregnant but not non-pregnant patients. Future work should focus on tailoring evidence-based immunization practices or developing new approaches to specifically fit busy ob-gyn offices.     

Insights into the protective effects of influenza vaccination: More hospitalizations but lower follow-up mortality during the 2014/15 influenza season in a Swiss cohort

BackgroundObservational studies of influenza vaccination are criticized as flawed due to unmeasured confounding. The goal of this cohort study was to explore the value and role of secondary claims data to inform the effectiveness of influenza vaccination, while systematically trying to reduce potential bias.MethodsWe iteratively reviewed the components of the PICO approach to refine study design. We analyzed Swiss mandatory health insurance claims of adult patients with chronic diseases, for whom influenza vaccination was recommended in 2014. Analyzed outcomes were all-cause mortality, hospitalization with a respiratory infection or its potential complication, and all-cause mortality after such hospitalization, adjusting for clinical and health care use variables. Cox and multi-state models were applied for time-to-event analysis.ResultsOf 343,505 included persons, 22.4% were vaccinated. Vaccinated patients were on average older, had more morbidities, higher health care expenditures, and had been more frequently hospitalized. In non-adjusted models, vaccination was associated with increased risk of events. Adding covariates decreased the hazard ratio (HR) both for mortality and hospitalizations. In the full model, the HR [95% confidence interval] for mortality during season was 0.82 [0.77–0.88], and closer to null effect after season. In contrast, HR for hospitalizations was increased during season to 1.28 [1.15–1.42], with estimates closer to null effect after season. HR in multi-state models were similar to those in the single-outcome models, with HR of mortality after hospitalization negative both during and after season.ConclusionIn patients with chronic diseases, influenza vaccination was associated with more frequent specific hospitalizations, but decreased risk of mortality overall and after such hospitalization. Our approach of iteratively considering PICO elements helped to consider various sources of bias in the study sequentially. The selection of appropriate, specific outcomes makes the link between intervention and outcome more plausible and can reduce the impact of confounding.     

Knowledge,attitudes, and practices regarding seasonal influenza vaccination during pregnancy in Costa Rica: A mixed-methods study

BackgroundInfluenza increases stillbirth risk, morbidity and mortality in pregnant women. Vaccination protects pregnant women against severe disease and indirectly protects their infants, but coverage among pregnant women remains low worldwide. We aimed to describe knowledge, attitudes, and practices (KAP) regarding seasonal influenza vaccination among postpartum women and prenatal care physicians in Costa Rica.MethodsWe conducted cross-sectional KAP surveys to women one to three days after childbirth at Costa Rican Social Security Fund maternity hospitals, and obstetricians and general practitioners who provided prenatal care in 2017. Principal components analysis, multiple imputation, and logistic regression were used to examine associations between influenza vaccination and demographics, prenatal care, and sources of information—separately for postpartum women and physicians. We also held two focus groups of six healthcare workers each to further describe vaccination KAP.ResultsWe surveyed 642 postpartum women and 146 physicians in maternity hospitals in five Costa Rican provinces of whom 85.5 % (95 % CI: 82.6 %-88.0 %) and 57.9 % (95 % CI: 49.6 %-65.7 %) were vaccinated for influenza, respectively. Factors associated with influenza vaccination for postpartum women included tetanus vaccination (aOR: 3.62, 95 % CI: 1.89–6.92); received vaccination recommendations from clinicians during prenatal check-ups (aOR: 3.39, 95 % CI: 2.06–5.59); had other children in household vaccinated for influenza (aOR: 2.25, 95 % CI: 1.08–4.68); and secondary/university education (aOR: 0.15–0.31) with no formal education as reference. For postpartum women, reasons for vaccination were perceived benefits for mother and infant, whereas not being offered vaccines was most cited for non-vaccination. Most prenatal care physicians recommended influenza vaccines during prenatal check-ups but believed vaccination causes flu-like symptoms.ConclusionVaccination campaigns and provisions of free vaccines effectively increased knowledge and coverage among women in Costa Rica. To improve access, women should be offered vaccines during prenatal care appointments. Educating healthcare workers about vaccine benefits for themselves and patients is needed to mitigate safety concerns.     

Respiratory syncytial virus and influenza hospitalizations in Danish children 2010–2016

ObjectiveTo pave the way for universal or risk factor-based vaccination strategies, the present study aimed to describe the epidemiology and compare risk factors for hospitalization associated with respiratory syncytial virus (RSV) and influenza virus infections in Danish children.MethodsNational register-based cohort study among 403,422 Danish children born 2010–2016.ResultsPrior asthma hospitalization, number of children in the household, chronic disease and maternal history of asthma hospitalization were the most important risk factors for both RSV and influenza hospitalization. The incidence of influenza increased at school start.ConclusionsOur findings enable targeted vaccination programs for high-risk children with asthma-like disease, chronic disease, siblings in the household, or maternal history of asthma hospitalization.     

Safety of guidelines recommending live attenuated influenza vaccine for routine use in children and adolescents with asthma

ObjectiveEvaluate whether a guideline recommending Live Attenuated Influenza Vaccine (LAIV) for children 2 years and older with asthma increased risks for lower respiratory events (LREs), within 21 or 42 days of vaccination, as compared to standard guidelines to administer Inactivated Influenza Vaccine (IIV) in children with asthma.MethodsThis was a pre/post guideline retrospective cohort study of children ages 2–17 years with asthma and receiving one or more influenza vaccines in two large medical groups from 2007 to 2016. Both groups recommended IIV in the pre-period; in 2010, one group implemented a guideline recommending LAIV for all children, including those with asthma. Main outcomes were medically attended LREs within 21 and 42 days after influenza immunization. Analysis used a generalized estimating equation regression to estimate the ratio of rate ratios (RORs) comparing pre/post events between LAIV guideline and control group.ResultsThe cohort included 7851 influenza vaccinations in 4771 children with asthma. Among patients in the LAIV guideline group, the proportion receiving LAIV increased from 23% to 68% post-guideline implementation, versus an increase from 7 to 11% in the control group. Age and baseline asthma severity adjusted ROR showed no increase in LREs, primarily asthma exacerbations, following implementation of the LAIV guideline: overall aROR (95% Confidence Interval): 0.74 (0.43–1.29) for LRE within 21 days of vaccination, 0.77 (0.53–1.14) for LRE within 42 days of vaccination. For the subset of children ages 2–4 years aROR: 0.92 (0.34–2.53) for LRE within 21 days of vaccination and 0.94 (0.49–1.82) for LRE within 42 days of vaccination; for children 5–18 years aROR (95% CI): 0.58 (0.26–1.30) for LRE within 21 days of vaccination and 0.67 (0.37–1.23) for LRE within 42 days.ConclusionIn a large cohort of children with asthma, a guideline recommending LAIV rather than IIV did not increase LREs following vaccination.