Objectives To assess the safety of live attenuated influenza vaccine (LAIV) in children in high-risk groups.
Design Non-interventional cohort study.
Setting England during 2013–2014 and 2014–2015 influenza seasons.
Participants LAIV recipients identified from the Clinical Practice Research Datalink, aged 2–17 years, and with at least one underlying high-risk condition. LAIV recipients were matched with inactivated influenza vaccine (IIV) recipients and unvaccinated controls.
Primary outcome measures Primary safety endpoints were any hospitalisation documented in the linked Hospital Episodes Statistics database within 42 days and up to 6 months after vaccination.
Results 11 463 children and adolescents were included: 4718 received the trivalent LAIV formulation during the 2013–2014 influenza season and 6745 received the quadrivalent formulation during the 2014–2015 influenza season. The risks of hospitalisation within 42 days were 231 per 1000 person-years (95% CI 193 to 275) in season 2013–2014 and 231 (95% CI 198 to 267) in season 2014–2015. These risks were not significantly different when compared with matched unvaccinated children (relative risks (RR) 0.96 (95% CI 0.78 to 1.19) in season 2013–2014, 0.90 (95% CI 0.76 to 1.07) in season 2014–2015) and consistently lower than after IIV administration (RR 0.47 (95% CI: 0.37 to 0.59) in season 2013–2014, 0.42 (95% CI 0.35 to 0.51) in season 2014–2015). A similar pattern was observed up to 6 months postvaccination with a risk of hospitalisation after LAIV administration that did not differ from what was observed in unvaccinated controls and was lower than after IIV administration.
Conclusions This study did not identify new safety concerns associated with the administration of LAIV in children and adolescents with high-risk conditions. However, as with any other observational study, treatment administration was not randomly assigned and our findings may be confounded by differences between the groups at baseline.
Trial registration number EUPAS18527.
- live attenuated influenza vaccine
- post-licensure safety
- high-risk conditions
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Contributors CSA and HC contributed to the study design. HC and AS contributed to the acquisition of data and data analysis. All authors contributed to interpretation of data, revised the manuscript critically for important intellectual content and approved the final version to be published.
Funding This study was sponsored by AstraZeneca. The funder provided support in the form of salaries for authors HC, RMM and CSA and funding to AS to conduct the study. Members of AstraZeneca were permitted to review the manuscript and offer comments, but the authors decided whether or not to address these comments.
Disclaimer AstraZeneca did not have any additional role in the study design, data collection and analysis, decision to publish or preparation of the manuscript.
Competing interests HC, RMM and CSA are full-time employees of AstraZeneca. Amy Steffey is an independent contractor who received funding from AstraZeneca for the data management and analysis of this study.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All source data were obtained from the Clinical Practice Research Datalink (CPRD) and linked with the Hospital Episodes Statistics database. Those data sources are made available for scientific and medical research after submission of a study protocol to be reviewed and approved by the CPRD Independent Scientific Advisory Committee (ISAC). All aggregate data from the study were presented in this manuscript. The only relevant data that were not shared are patient-level data for children presenting adverse events, consistently with the data privacy rules set up by CPRD/ISAC.
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