Safety of Intranasal Quadrivalent Live Attenuated Influenza Vaccine (QLAIV) in Children and Adolescents: A Pilot Prospective Cohort Study in England

INTRODUCTION Fluenz Tetra is an intranasal quadrivalent live attenuated influenza vaccine (QLAIV) and is recommended as the vaccine of choice for children in the 2014/2015 influenza season vaccination programme in the UK. OBJECTIVE The primary objective of the study was to estimate the crude incidence rate of adverse events of interest (AEIs) following vaccination with the nasal QLAIV early in the 2014/2015 influenza season in children and adolescents in England. METHODS A pilot non-interventional cohort post-authorisation safety study (PASS) was conducted during the 2014/2015 influenza season in England. Vaccinees were recruited via the mass vaccination programme in England. Participant outcomes, validated by a healthcare professional (general practitioner) where appropriate, were captured through questionnaires (surface mail, telephone, e-questionnaire). Data analysis comprised descriptive statistics and calculation of event risks and incidence rates, stratified by age group and selected co-morbidities. RESULTS The final evaluable cohort consisted of 385 participants; the median (interquartile range) age was 4 (3-9) years with a range of 2-17 years, and 53.2 % were female. The most frequently reported AEI was nasal congestion (n = 167; 43.4 %; 312.3 per 1000 patient-weeks [95 % CI 267.3-364.8]). Further frequently reported AEIs were malaise (n = 87; 22.6 %; 123.4 per 1000 patient-weeks [95 % CI 98.9-154.1]) and cough (n = 80; 20.8 %; 118.5 per 1000 patient-weeks [95 % CI 95.1-147.8]). Five hypersensitivity-type reactions were reported, although on follow-up none were true hypersensitivity reactions or required hospitalisation. No serious adverse events (SAEs) were reported, with no hospitalisations or deaths. No significant change in reactogenicity or other apparent safety signals was detected as part of this study. CONCLUSION The pilot study showed no significant change in reactogenicity or other apparent safety signals from the data collected. Continued enhanced surveillance of seasonal influenza vaccines will ensure their ongoing safety for the prevention of serious illness from seasonal influenza outbreaks.