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The impact of repeated vaccination on relative influenza vaccine effectiveness among vaccinated adults in the United Kingdom

Lim, Wey Wen; Cowling, Benjamin J; Nakafero, Georgina; Feng, Shuo; Nguyen-Van-Tam, Jonathan S; Bolt, Hikaru


Wey Wen Lim

Benjamin J Cowling

Shuo Feng

Hikaru Bolt


Annual seasonal influenza vaccination is recommended for individuals at high risk of developing post-infection complications in many locations. However, reduced vaccine immunogenicity and effectiveness have been observed among repeat vaccinees in some influenza seasons. We investigated the impact of repeated influenza vaccination on relative vaccine effectiveness (VE) among individuals who were recommended for influenza vaccination in the United Kingdom with a retrospective cohort study using primary healthcare data from the Clinical Practice Research Datalink (CPRD), a primary care database in the United Kingdom. Relative VE was estimated against general practitioner-diagnosed influenza-like illnesses (GP-ILI) and medically attended acute respiratory illnesses (MAARI) among participants who have been repeatedly vaccinated compared with first-time vaccinees using proportional hazards models. Relative VE against MAARI may be reduced for individuals above 65 years old who were vaccinated in the current and previous influenza seasons for some influenza seasons. However, these findings were not conclusive as we could not exclude the possibility of residual confounding in our dataset. The use of routinely collected data from electronic health records to examine the effects of repeated vaccination needs to be complemented with sufficient efforts to include negative control outcomes to rule out residual confounding.


Lim, W. W., Cowling, B. J., Nakafero, G., Feng, S., Nguyen-Van-Tam, J. S., & Bolt, H. (2022). The impact of repeated vaccination on relative influenza vaccine effectiveness among vaccinated adults in the United Kingdom. Epidemiology and Infection, 150, Article E198.

Journal Article Type Article
Acceptance Date Oct 28, 2022
Online Publication Date Nov 4, 2022
Publication Date Nov 4, 2022
Deposit Date Nov 3, 2022
Publicly Available Date Nov 3, 2022
Journal Epidemiology and Infection
Print ISSN 0950-2688
Electronic ISSN 1469-4409
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 150
Article Number E198
Keywords Infectious Diseases; Epidemiology
Public URL
Publisher URL


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