The effectiveness of maternal pertussis vaccination in protecting newborn infants in Brazil: A case-control study

IntroductionIn 2014, the Brazilian Ministry of Health (MoH) recommended Tdap to pregnant women in response to a significant increase in the incidence of pertussis among infants. The present study assessed the effectiveness of maternal immunization in preventing pertussis in infants.MethodsAn unmatched case-control study was undertaken in São Paulo State, Brazil from February 2015 to July 2016. Cases were infants aged <8 weeks at onset of pertussis reported to the Surveillance System and confirmed by real-time polymerase chain reaction or culture. Four to six healthy infants were selected as controls per case from birth certificates in the Information System on Live Births database. General characteristics and mother’s vaccination status were compared between cases and controls. The vaccine effectiveness (VE) was calculated as 1 – odds ratio (OR). For the adjusted VE, the OR was calculated using logistic regression analysis.ResultsForty-two cases and 248 controls were enrolled in the study. Mothers of 8 cases (19.1%) and 143 controls (57.4%) were vaccinated during pregnancy, resulting in an unadjusted VE of 82.6% (95% confidence interval [CI], 60.8–92.3%). The VE was unchanged after adjusting for maternal age and monthly household income.ConclusionMaternal pertussis vaccination during pregnancy was effective in protecting infants aged <8 weeks from pertussis.     

Immunogenicity,transplacental transfer of pertussis antibodies and safety following pertussis immunization during pregnancy: Evidence from a randomized,placebo-controlled trial

BackgroundPertussis immunization during pregnancy is recommended in many countries. Data from large randomized controlled trials are needed to assess the immunogenicity, reactogenicity and safety of this approach.MethodsThis phase IV, observer-blind, randomized, placebo-controlled, multicenter trial assessed immunogenicity, transplacental transfer of maternal pertussis antibodies, reactogenicity and safety of a reduced-antigen-content diphtheria-tetanus-three-component acellular pertussis vaccine (Tdap) during pregnancy. Women received Tdap or placebo at 27–36 weeks’ gestation with crossover ≤ 72-hour-postpartum immunization. Immune responses were assessed before the pregnancy dose and 1 month after, and from the umbilical cord at delivery. Superiority (primary objective) was reached if the lower limits of the 95% confidence intervals (CIs) of the pertussis geometric mean concentration (GMC) ratios (Tdap/control) in cord blood were ≥ 1.5. Solicited and unsolicited adverse events (AEs) and pregnancy-/neonate-related AEs of interest were recorded.Results687 pregnant women were vaccinated (Tdap: N = 341 control: N = 346). Superiority of the pertussis immune response (maternally transferred pertussis antibodies in cord blood) was demonstrated by the GMC ratios (Tdap/control): 16.1 (95% CI: 13.5–19.2) for anti-filamentous hemagglutinin, 20.7 (15.9–26.9) for anti-pertactin and 8.5 (7.0–10.2) for anti-pertussis toxoid. Rates of pregnancy-/neonate-related AEs of interest, solicited general and unsolicited AEs were similar between groups. None of the serious AEs reported throughout the study were considered related to maternal Tdap vaccination.ConclusionsTdap vaccination during pregnancy resulted in high levels of pertussis antibodies in cord blood, was well tolerated and had an acceptable safety profile. This supports the recommendation of Tdap vaccination during pregnancy to prevent early-infant pertussis disease.Clinical Trial Registration. ClinicalTrials.gov: NCT02377349.     

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.     

Inactivated influenza vaccine and spontaneous abortion in the Vaccine Safety Datalink in 2012–13, 2013–14, and 2014–15

IntroductionA recent study reported an association between inactivated influenza vaccine (IIV) and spontaneous abortion (SAB), but only among women who had also been vaccinated in the previous influenza season. We sought to estimate the association between IIV administered in three recent influenza seasons and SAB among women who were and were not vaccinated in the previous influenza season.MethodsWe conducted a case-control study over three influenza seasons (2012–13, 2013–14, 2014–15) in the Vaccine Safety Datalink (VSD). Cases (women with SAB) and controls (women with live births) were matched on VSD site, date of last menstrual period, age group, and influenza vaccination status in the previous influenza season. Of 1908 presumptive cases identified from the electronic record, 1236 were included in the main analysis. Administration of IIV was documented in several risk windows, including 1–28, 29–56, and >56 days before the SAB date.ResultsAmong 627 matched pairs vaccinated in the previous season, no association was found between vaccination in the 1–28 day risk window and SAB (adjusted odds ratio (aOR) 0.9; 95% confidence interval (CI) 0.6–1.5). The season-specific aOR ranged from 0.5 to 1.7 with all CIs including the null value of 1.0. Similarly, no association was found among women who were not vaccinated in the previous season; the season-specific aOR in the 1–28 day risk window ranged from 0.6 to 0.7 and the 95% CI included 1.0 in each season. There was no association found between SAB and influenza vaccination in the other risk windows, or when vaccine receipt was analyzed relative to date of conception.ConclusionDuring these seasons we found no association between IIV and SAB, including among women vaccinated in the previous season. These findings lend support to current recommendations for influenza vaccination at any time during pregnancy, including the first trimester.     

Influenza vaccination uptake among Canadian adults before and during the COVID-19 pandemic: An analysis of the Canadian Longitudinal study on Aging (CLSA)

IntroductionUnderstanding how influenza vaccine uptake changed during the 2020/2021 influenza season compared to previous pre-pandemic seasons is a key priority, as is identifying the relationship between prior influenza vaccination and COVID-19 vaccine willingness.MethodsWe analyzed data from a large, nationally representative cohort of Canadian residents aged 50 and older to assess influenza vaccination status three times between 2015 and 2020. We investigated: 1) changes in self-reported influenza vaccine uptake, 2) predictors of influenza vaccine uptake in 2020/2021, and 3) the association between influenza vaccination history and self-reported COVID-19 vaccine willingness using logistic regression models.ResultsAmong 23,385 participants analyzed for aims 1–2, influenza vaccination increased over time: 14,114 (60.4%) in 2015–2018, 15,692 (67.1%) in 2019/2020, and 19,186 (82.0%; combining those already vaccinated and those planning to get a vaccine) in 2020/2021. After controlling for socio-demographics, history of influenza vaccination was most strongly associated with influenza vaccination in 2020/2021 (adjusted odds ratio [aOR] 147.9 [95% CI: 120.9–180.9]); this association remained after accounting for multiple health and pandemic-related factors (aOR 140.3 [95% CI: 114.5–171.8]). To a lesser degree, those more concerned about COVID-19 were also more likely to report influenza vaccination in fall 2020, whereas those reporting a very negative impact of the pandemic were less likely to get vaccinated. Among 23,819 participants with information on COVID-19 vaccine willingness during the last quarter of 2020 (aim 3), prior influenza vaccination was most strongly associated with willingness to get a COVID-19 vaccine (aOR 15.1 [95% CI: 13.5–16.8] for those who had received influenza vaccine at all previous timepoints versus none).ConclusionsOur analysis highlights the importance of previous vaccination in driving vaccination uptake and willingness. Efforts to increase vaccination coverage for influenza and COVID-19 should target individuals who do not routinely engage with immunization services regardless of demographic factors.     

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.     

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.     

Prenatal tetanus-diphtheria-acellular pertussis vaccine effectiveness at preventing infant pertussis

ObjectiveTo evaluate the effectiveness of the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine containing five pertussis components (Tdap5; Adacel®, Sanofi) when given during pregnancy at preventing pertussis in infants less than 2 months of age.MethodsThe US Centers for Disease Control and Prevention (CDC), in collaboration with the Emerging Infections Program (EIP) Network, undertook a case-control study evaluating the effectiveness of Tdap vaccination in pregnancy against pertussis in infants less than 2 months of age based on data collected by the EIP Network from 2011 through 2014. The dataset from the CDC/EIP Network study was used to conduct this product-specific vaccine effectiveness analysis of Tdap5 vaccination in pregnancy to prevent disease in young infants. The main outcome of interest was vaccine effectiveness in infants whose pregnant parents were vaccinated with Tdap5 between 27 and 36 weeks’ gestation, in accordance with the ideal timing for Tdap vaccination in pregnancy recommended by the US Advisory Committee on Immunization Practices. Odd ratios (ORs) and 95 % confidence intervals (CIs) were estimated using conditional logistic regression, and vaccine effectiveness was calculated as (1–OR) × 100 %.ResultsThere were 160 infant pertussis cases and 302 matched controls included in this Tdap5-specific study. Tdap5 effectiveness in preventing pertussis in infants whose pregnant parents were vaccinated between 27 and 36 weeks’ gestation was 92.5 % (95 % CI, 38.5 %–99.1 %). Effectiveness of Tdap5 against pertussis-related hospitalization in infants whose pregnant parents were vaccinated between 27 and 36 weeks’ gestation could not be calculated due to lack of discordance among matched cases and controls. Vaccination of the parents after pregnancy or less than 14 days before delivery did not protect infants from pertussis.ConclusionsTdap5 vaccination in pregnancy between 27 and 36 weeks’ gestation is highly effective at protecting young infants from pertussis.Study registration: ClinicalTrials.gov, NCT05040802.     

Meningococcal B vaccination coverage among older adolescents in the United States

BackgroundSerogroup B meningococcal (MenB) vaccination recommendations for adolescents in the United States (US) include routine vaccination for all individuals at increased risk and vaccination for individuals not at increased risk aged 16–23 years (preferred age 16–18 years) based on shared clinical decision-making. The two licensed MenB vaccines require administration of ≥2 doses.MethodsThis cross-sectional study analyzed 2017–2018 National Immunization Survey-Teen (NIS-Teen) data to evaluate ≥1 dose and ≥2 dose MenB vaccination coverage among adolescents aged 17 years. Multivariable logistic regression was used to further evaluate determinants of MenB vaccination.ResultsNationally, MenB vaccination coverage among 17-year-olds increased from 14.5% in 2017 to 17.2% in 2018 for ≥1 dose and from 6.3% to 8.4% for ≥2 doses. MenB vaccination coverage (2017–2018) was the lowest in the South (≥1 dose: 14.6%; ≥2 doses: 6.3%) and highest in the Northeast region (18.3% and 9.3%), with variation observed by census division. Adolescents were more likely to have received ≥1 dose of MenB vaccine if they had any Medicaid insurance (odds ratio [OR], 1.77; 95% confidence interval [CI], 1.32–2.39) or had received human papillomavirus (OR, 1.94; 95% CI, 1.41–2.67) or meningococcal A, C, W, and Y (OR, 4.03; 95% CI, 2.92–5.56) vaccinations.ConclusionsMenB first-dose coverage in the US is low, and even lower for a second dose, with regional variation. Being up to date with other routinely administered vaccines increased the likelihood of receiving MenB vaccination.     

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.     

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.     

Trivalent inactivated influenza vaccine (IIV3) during pregnancy and six-month infant development

ObjectiveDespite recommendations by professional organizations that all pregnant women receive inactivated influenza vaccine, safety concerns remain a barrier. Our objective was to assess the effect of trivalent influenza vaccines (IIV3) during pregnancy on parent report 6-month infant development.MethodsWe conducted a multi-site prospective birth cohort study during the 2010–2011 influenza season and followed pregnant women and their newborns through 6 months of age. Information on IIV3 during pregnancy was ascertained from the EHR and self-report. The Ages and Stages Questionnaire-3 (ASQ-3) was completed by the mother to assess 6-month infant neurodevelopment in five domains (communication, gross motor, fine motor, problem-solving, and personal adaptive skills). Scores for each domain above the cut-off point indicating typical development were categorized as “on schedule” while scores in the zones indicating the need for either monitoring or further assessment were categorized as “not on schedule”. Multivariable logistic regression was conducted.ResultsOf the 1225 infant-mother pairs, 65% received IIV3 during pregnancy. In bivariate analysis, infants of women who received IIV3 during pregnancy were moderately-less likely to need monitoring or further assessment in the personal social domain compared with infants of unvaccinated women (10.0% vs. 14.1%, p = 0.033; crude OR (cOR): 0.68(95%CI:0.48,0.97)). However, after controlling for potential confounders, the findings were no longer statistically significant (aOR:0.72,95%CI: 0.49,1.06,p = 0.46). No significant unadjusted or adjusted associations emerged in any other ASQ-3 domain.ConclusionThere was no significant association between IIV3 exposure during pregnancy and 6-month infant development. Studies of IIV3 during pregnancy to assess longer-term developmental outcomes are indicated.     

Timeliness and factors associated with rotavirus vaccine uptake among Australian Aboriginal and non-Aboriginal children: A record linkage cohort study

ObjectivesRotavirus vaccines (RV), included in Australia’s National Immunisation Program from mid-July 2007, are unique in strict time limits for administration. Here, we report on timeliness of RV uptake, compare cumulative RV coverage to age 12 months with DTPa, and assess factors associated with receipt of RV among Aboriginal and non-Aboriginal children.MethodsBirth records for 681,456 children born in two Australian states in 2007–2012 were probabilistically linked to national immunisation records. We assessed on-time coverage (defined as receipt of vaccine dose between 4 days prior to scheduled date and the recommended upper limit) for RV and compared this to diphtheria-tetanus-pertussis (DTPa) vaccine. Logistic regression modelling was used to assess independent determinants of receipt of RV.ResultsCompared to non-Aboriginal infants, on-time RV coverage was lower for all doses among Aboriginal infants. Post the upper age limit of RV dose2, DTPa dose2 coverage increased by 9–16% to ≥90%, whereas RV coverage remained around 77% (Aboriginal) and 85% (non-Aboriginal). Compared to first-born children, the adjusted odds of receiving ≥1 RV dose if born to a mother with ≥3 previous births was 0.30 (95%CI: 0.27–0.34) among Aboriginal, and 0.53 (95%CI: 0.51–0.55) among non-Aboriginal children. Prematurity (<33 weeks), low birthweight (<1500 g), maternal age <20 years, maternal smoking during pregnancy and living in a disadvantaged area were independently associated with decreased vaccine uptake.ConclusionsAboriginal children are at greater risk of rotavirus disease than non-Aboriginal children and delayed vaccine receipt is substantially higher. Although specific programs targeting groups at risk of delayed vaccination might improve RV coverage, relaxation of upper age restrictions is most readily implementable, and its overall risk-benefit should be evaluated.     

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.     

Effectiveness of seasonal influenza vaccine in adult Japanese workers, 2017–2020

BackgroundPrevious studies have not estimated vaccine effectiveness (VE) against influenza in the working-age Japanese population. In this study, we determined VE in adult workers at a Japanese company.MethodsWe estimated VE based on self-reported data regarding influenza infections and vaccinations in employees of an auto parts manufacturing company during three influenza seasons from 2017 to 2020. VE was estimated as 100% × [1 ? odds ratio (the ratio of the odds of being diagnosed with influenza among enrollees with and without influenza vaccination)]. Odds ratios were estimated using logistic regression.ResultsWe included 11,347 worker records [3,592 (2017–18), 3,663 (2018–19), and 4,092 (2019–20)] from employees who had worked with the company throughout each influenza season. The adjusted VE was moderate and significant in the 2019–20 season (VE = 53%; 95% confidence interval [CI] = 30% to 69%) but low or negative and non-significant during the 2017–18 (VE = 28%; 95% CI = -5% to 50%) and 2018–19 (VE = -11%; 95% CI =  - 42% to 14%) seasons.ConclusionsInfluenza vaccines were moderately effective during the 2019–20 season but showed low or negative effectiveness during the 2017–18 and 2018–19 seasons. Self-reports from worker records can successfully help determine VE against influenza.     

Statin use and medically attended acute respiratory illness among influenza vaccine recipients

BackgroundPrevious studies have suggested that statins decrease influenza vaccine effectiveness and increase risk of medically attended acute respiratory illness (MAARI).ObjectivesTo examine the association of incident statin use and MAARI in a cohort of influenza vaccine recipients.MethodsThis retrospective cohort study evaluated influenza vaccine recipients within the Tricare population. The primary outcome compared MAARI incidence during the follow-up period in a propensity score-matched cohort of incident statin users and statin non-users. Secondary analysis included propensity score-adjusted comparisons between incident statin users and statin non-users in the entire cohort and prespecified sub-cohorts with and without comorbidities. The propensity score was derived from 72 variables encompassing demographics, medical history, comorbidities, medication use, and healthcare utilization.ResultsMAARI incidence in statin users was similar to non-users in the propensity score-matched cohort (odds ratio [OR] 0.92; 95% confidence interval [CI] 0.84–1.01). In contrast, statin users with lower comorbidity had lower OR for MAARI compared to non-users (Charlson Score zero cohort: 0.85 [CI 0.74–0.98]; No Diabetes cohort: 0.88 [CI 0.80–0.96]).ConclusionIncident statin use was not associated with increased MAARI incidence and may be associated with lower incidence of MAARI in those with less comorbidity. This study thus offers reassurance regarding the effectiveness of the influenza vaccine in statin users.     

Surveillance for Guillain-Barré syndrome after influenza vaccination among U.S. Medicare beneficiaries during the 2017–2018 season

BackgroundThe U.S. Food and Drug Administration and the Centers for Medicare & Medicaid Services have been actively monitoring the risk of Guillain-Barré syndrome (GBS) following influenza vaccination among Fee-for-Service (FFS) Medicare beneficiaries every season since 2008. We present our evaluation of the GBS risk following influenza vaccinations during the 2017–2018 season.MethodsWe implemented a multilayered approach to active safety surveillance that included near real-time surveillance early in the season, comparing GBS rates post-vaccination during the 2017–2018 season with rates from five prior seasons using the Updating Sequential Probability Ratio Test (USPRT), and end-of-season self-controlled risk interval (SCRI) analyses.ResultsWe identified approximately 16 million influenza vaccinations. The near real-time surveillance did not signal for a potential 2.5-fold increased GBS risk either in days 8–21 or 1–42 post-influenza vaccination. In the SCRI analyses, we did not detect statistically significant increased GBS risks among influenza-vaccinated Medicare beneficiaries ≥65 years for either the 8–21 or 1–42-day risk windows for all seasonal vaccines combined, high-dose vaccine, or standard-dose vaccines; we did detect an increased GBS risk in days 8–21 post-vaccination for individuals vaccinated with the adjuvanted vaccine (OR: 3.75; 95% CI: 1.01, 13.96), although this finding was not statistically significant after multiplicity adjustment (p = 0.146).ConclusionsOur multilayered surveillance approach—which allows for early detection of elevated GBS risk and provides reliable end-of-season SCRI estimates of effect size—did not identify an increased GBS risk following 2017–2018 influenza vaccinations. The slightly increased GBS risk with the adjuvanted vaccine, which was not statistically significant following multiplicity adjustment, is consistent with the package inserts of all U.S.-licensed influenza vaccines, which warn of a potential low increased GBS risk. The benefits of influenza vaccines in preventing morbidity and mortality heavily outweigh this potential risk.     

School immunization coverage in adolescents during the COVID-19 pandemic: A retrospective cohort study

IntroductionFew studies have assessed the impact of the coronavirus disease 2019 (COVID-19) pandemic on immunization coverage for adolescents, and little is known about how coverage has changed throughout the pandemic. We aimed to: (1) assess the change in coverage for school-based vaccines in Alberta, Canada resulting from the pandemic; (2) determine whether coverage differed by geographic health zone and school type; and (3) ascertain whether coverage has returned to pre-pandemic levels.MethodsUsing a retrospective cohort design, we used administrative health data to compare coverage for human papillomavirus (HPV) and meningococcal conjugate A, C, Y, W-135 (MenC-ACYW) vaccines between pre-pandemic (2017–2018 school year) and pandemic (2019–2020 and 2020–2021 school years) cohorts (N = 289,420). Coverage was also compared by health zone and authority type. The 2019–2020 cohort was followed over one year to assess catch-up.ResultsCompared to 2017–2018, immunization coverage for HPV was significantly lower in the 2019–2020 (absolute difference: 60.8%; 95% CI: 60.4–61.3%) and 2020–2021 cohorts (absolute difference: 59.9%; 95% CI: 59.4–60.3%). There was a smaller, significant decline in MenC-ACYW coverage comparing 2017–2018 to 2019–2020 (absolute difference: 6.1%; 95% CI: 5.6–6.5%) and 2020–2021 (absolute difference: 32.2%; 95% CI: 31.6–32.7%). Private schools had low coverage overall, while coverage fluctuated by zone. During follow-up of the 2019–2020 cohort, coverage for HPV and MenC-ACYW increased from 5.6% to 50.2%, and 80.7% to 83.0%, respectively.ConclusionThere was a substantial decrease in school-based immunization coverage during the COVID-19 pandemic, and coverage has not returned to pre-pandemic levels, suggesting further catch-up is needed.