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

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 21; no. 38; p. 1
• Main Authors: Nohynek, Hanna, Baum, Ulrike, Syrjänen, Ritva, Ikonen, Niina, Sundman, Jonas, Jokinen, Jukka
• Format: Journal Article
• Language: English
• Published: Sweden Centre Europeen pour la Surveillance Epidemiologique du SIDA (European Centre for the Epidemiological Monitoring of AIDS) 22.09.2016; European Centre for Disease Prevention and Control (ECDC)
• Subjects: Child, Preschool; Children & youth; Cohort Studies; Effectiveness; Female; Finland - epidemiology; Follow-Up Studies; Humans; Immunization Programs; Influenza; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - immunology; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - epidemiology; Influenza, Human - immunology; Influenza, Human - prevention & control; Laboratories; Male; Outcome Assessment (Health Care); Polymerase Chain Reaction; Seasons; Sentinel Surveillance; Surveillance and Outbreak Report; Vaccination - statistics & numerical data; Vaccines; Vaccines, Attenuated - administration & dosage; Vaccines, Attenuated - immunology; Vaccines, Inactivated - administration & dosage; Vaccines, Inactivated - immunology; Finland; influenza; immunisation; vaccines; live attenuated vaccine, inactivated vaccine, children
• ISSN: 1560-7917; 1025-496X; 1560-7917
• DOI: 10.2807/1560-7917.es.2016.21.38.30346

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.