Effectiveness of the live attenuated and the inactivated influenza vaccine in two-year-olds – a nationwide cohort study Finland, influenza season 2015/16

Abstract

Although widely recommended, influenza vaccination of children is part of the national vaccination programme only in few countries. In addition to Canada and the United States (US), in Europe Finland and the United Kingdom have introduced live attenuated influenza vaccine (LAIV) for healthy children in their programmes. On 22 June 2016, the US Advisory Committee on Immunizations Practices, voted against further use of LAIV due to no observed vaccine effectiveness (VE) over three consecutive influenza seasons (2013/14 to 2015/16). We summarise the results of a nationwide, register-based cohort study (N=55,258 of whom 8,086 received LAIV and 4,297 TIV); all outcome (laboratory-confirmed influenza), exposure (vaccination) and confounding variable data were retrieved from four computerised national health registers, which were linked via a unique personal identity code assigned to all permanent Finnish residents regardless of nationality. Our study provides evidence of moderate effectiveness against any laboratory-confirmed influenza of the quadrivalent LAIV vaccine (VE: 51%; 95% confidence interval (CI): 28–66%) as well as the inactivated trivalent vaccine (VE: 61%; 95% CI: 31–78%) among two-year-olds during the influenza season 2015/16 in Finland. Based on these data, Finland will continue using LAIV for young children in its National Immunisation Programme this coming influenza season.

Influenza Vaccine Effectiveness in the United States during the 2015–2016 Season

“…23 A Finnish cohort study involving 2-year-old children showed a significant vaccine effectiveness against influenza A — predominantly against A(H1N1)pdm09 — of 48% for the quadrivalent live attenuated vaccine and 80% for the trivalent inactivated vaccine. 24 Finally, a U.K. study involving children 2 to 17 years of age showed a non-significant vaccine effectiveness of 42% against A(H1N1)pdm09 for the quadrivalent live attenuated vaccine, as compared with an effectiveness of 100% for the trivalent inactivated vaccine. 25 In light of these data, the ACIP made an interim recommendation not to use the quadrivalent live attenuated vaccine in the United States for the 2016–2017 influenza season.…”

Summary of the NACI Statement on Seasonal Influenza Vaccine for 2017–2018

“…This article also presents information not provided in the published addenda or statement: figures summarizing the LAIV vaccine effectiveness data from the cited studies, by influenza season and influenza strain, as well as LAIV vaccine effectiveness data used to inform NACI's decision that were not publicly available when the Addendum was finalized, but have subsequently been published (30,31).…”

Live attenuated influenza vaccine (LAIV): recent effectiveness results from the USA and implications for LAIV programmes elsewhere

“…Among children 2 years of age eligible for vaccination, the LAIV4 VE was 47.9% (significant) for influenza A and 57.2% (non-significant) for B. This compares with an IIV VE of 79.5% for influenza A (significant) and -1% for influenza B (non-significant) 3. It is also noteworthy that previous vaccination with TIV improved VE both for LAIV and TIV.…”