Effects of Influenza Vaccination in the United States During the 2017–2018 Influenza Season

Abstract

Background The severity of the 2017–2018 influenza season in the United States was high, with influenza A(H3N2) viruses predominating. Here, we report influenza vaccine effectiveness (VE) and estimate the number of vaccine-prevented influenza-associated illnesses, medical visits, hospitalizations, and deaths for the 2017–2018 influenza season. Methods We used national age-specific estimates of 2017–2018 influenza vaccine coverage and disease burden. We estimated VE against medically attended reverse-transcription polymerase chain reaction–confirmed influenza virus infection in the ambulatory setting using a test-negative design. We used a compartmental model to estimate numbers of influenza-associated outcomes prevented by vaccination. Results The VE against outpatient, medically attended, laboratory-confirmed influenza was 38% (95% confidence interval [CI], 31%–43%), including 22% (95% CI, 12%–31%) against influenza A(H3N2), 62% (95% CI, 50%–71%) against influenza A(H1N1)pdm09, and 50% (95% CI, 41%–57%) against influenza B. We estimated that influenza vaccination prevented 7.1 million (95% CrI, 5.4 million–9.3 million) illnesses, 3.7 million (95% CrI, 2.8 million–4.9 million) medical visits, 109 000 (95% CrI, 39 000–231 000) hospitalizations, and 8000 (95% credible interval [CrI], 1100–21 000) deaths. Vaccination prevented 10% of expected hospitalizations overall and 41% among young children (6 months–4 years). Conclusions Despite 38% VE, influenza vaccination reduced a substantial burden of influenza-associated illness, medical visits, hospitalizations, and deaths in the United States during the 2017–2018 season. Our results demonstrate the benefit of current influenza vaccination and the need for improved vaccines.

Vaccine effectiveness against influenza A(H3N2) and B among laboratory‐confirmed, hospitalised older adults, Europe, 2017‐18: A season of B lineage mismatched to the trivalent vaccine

“…Adjusted IVE against hospitalised influenza A(H3N2) among the elderly in the European region was 24%, only slightly higher than that found in the previous 2016-17 season (17%). 7 which were below 50%, 8,9 as they have been for almost a decade. [10][11][12][13][14][15][16][17] A recent systematic review of studies using the test-negative design estimated a pooled IVE of 24% (95% CI: −6 to 45) against influenza A(H3N2) in older adults (>60 years) for the consecutive seasons 2004-2015.…”

“…Vaccination against influenza has been described as having low or very low effectiveness among the older adult population, 28 as well as among patients with these co-morbid conditions. [29][30][31][32][33] Yet, influenza vaccination is considered the best available public health intervention to protect against influenza infection, and there is evidence of reduction in severe outcomes from influenza (hospitalisation 8,34,35 or Adjusted for study site, sex, age (modelled as a linear term) and onset date (modelled using a restricted cubic spline [RCS] with 5 knots). g Adjusted for study site, sex, age (modelled using a RCS with 3 knots) and onset date (modelled using a RCS with 5 knots).…”

Put a cork in it: Plugging the M2 viral ion channel to sink influenza

“…While prophylactic vaccines can confer immunity against circulating virus strains, their effectiveness and extent of immunization coverage vary across populations from year to year. This variability contributed in part to the recent and notable 2017-2018 seasonal outbreak which is estimated by the Centers for Disease Control and Prevention to have caused approximately 710,000 hospitalizations and up to 79,400 deaths in the United States alone (CDC, 2018;Rolfes et al, 2019). Of particular concern are less common but historically regular pandemic outbreaks in populations with limited or no immunity that can result in hundreds of thousands to millions of deaths worldwide.…”

Serious outcomes of medically attended, laboratory‐confirmed influenza illness among school‐aged children with and without asthma, 2007‐2018

“…This is a secondary analysis of data from annual populationbased studies of influenza vaccine effectiveness conducted by Marshfield Clinic Research Institute in Marshfield, Wisconsin as part of the US Influenza Vaccine Effectiveness (US Flu VE) Network between 2007 and 2018. [20][21][22][23][24][25][26][27][28] In this community, residents receive nearly all outpatient and inpatient care from the Marshfield Clinic Health System, where both inpatient and outpatient records are accessible. 29 , was ≤7 days in duration, and they had not received antiviral medication before enrollment.…”