Abstract
BackgroundIn the United Kingdom (UK), in recent influenza seasons, children are offered a quadrivalent live attenuated influenza vaccine (LAIV4), and eligible adults mainly trivalent inactivated vaccine (TIV).AimTo estimate the UK end-of-season 2017/18 adjusted vaccine effectiveness (aVE) and the seroprevalence in England of antibodies against influenza viruses cultured in eggs or tissue.MethodsThis observational study employed the test-negative case–control approach to estimate aVE in primary care. The population-based seroprevalence survey used residual age-stratified samples.ResultsInfluenza viruses A(H3N2) (particularly subgroup 3C.2a2) and B (mainly B/Yamagata/16/88-lineage, similar to the quadrivalent vaccine B-virus component but mismatched to TIV) dominated. All-age aVE was 15% (95% confidence interval (CI): −6.3 to 32) against all influenza; −16.4% (95% CI: −59.3 to 14.9) against A(H3N2); 24.7% (95% CI: 1.1 to 42.7) against B and 66.3% (95% CI: 33.4 to 82.9) against A(H1N1)pdm09. For 2–17 year olds, LAIV4 aVE was 26.9% (95% CI: −32.6 to 59.7) against all influenza; −75.5% (95% CI: −289.6 to 21) against A(H3N2); 60.8% (95% CI: 8.2 to 83.3) against B and 90.3% (95% CI: 16.4 to 98.9) against A(H1N1)pdm09. For ≥ 18 year olds, TIV aVE against influenza B was 1.9% (95% CI: −63.6 to 41.2). The 2017 seroprevalence of antibody recognising tissue-grown A(H3N2) virus was significantly lower than that recognising egg-grown virus in all groups except 15–24 year olds.ConclusionsOverall aVE was low driven by no effectiveness against A(H3N2) possibly related to vaccine virus egg-adaption and a new A(H3N2) subgroup emergence. The TIV was not effective against influenza B. LAIV4 against influenza B and A(H1N1)pdm09 was effective.
Highlights
The United Kingdom (UK) has a long-standing selective influenza immunisation programme offering inactivated vaccine to persons ≥ 65 years of age and those aged months to 64 years of age with an underlying clinical risk factor
Six vaccinated cases aged between 2–17 years (three infected with influenza A(H3N2) and three infected with A(H1N1)pdm09) had no information on the type of vaccine (QIV or trivalent inactivated vaccine (TIV)) they received, so they are not included in the analyses presented in the table
The details of the 3,080 samples remaining stratified according to the swab result and by vaccination are described in Tables 1 and 2
Summary
The United Kingdom (UK) has a long-standing selective influenza immunisation programme offering inactivated vaccine to persons ≥ 65 years of age and those aged months to 64 years of age with an underlying clinical risk factor. By 2017/18, all children 2–8 years of age across the UK were being offered quadrivalent live attenuated influenza vaccine (LAIV4), with uptake higher than the previous season in targeted cohorts [2]. Ireland offered LAIV4 to all children of primary school age (including 9–11 years of age). In the United Kingdom (UK), in recent influenza seasons, children are offered a quadrivalent live attenuated influenza vaccine (LAIV4), and eligible adults mainly trivalent inactivated vaccine (TIV). Aim: To estimate the UK end-of-season 2017/18 adjusted vaccine effectiveness (aVE) and the seroprevalence in England of antibodies against influenza viruses cultured in eggs or tissue. All-age aVE was 15% (95% confidence interval (CI): −6.3 to 32) against all influenza;
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