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Abstract
Background Annual vaccination against influenza virus is generally recommended to elderly and chronically ill, but the relative importance of factors influencing the outcome is not fully understood. Methods In this study of 88 individuals all aged 69 years, the increase in haemagglutinin-inhibiting (HI) antibodies to trivalent inactivated influenza vaccine was correlated with HI titres before vaccination, prior vaccinations against influenza, cytomegalovirus serostatus and, as an estimate of immune risk profile, the ratio between CD4 + and CD8 + T cells. Results Vaccine responses were impaired by high pre-existing HI antibody titres. For influenza B repeated vaccinations and an inverse CD4/CD8 ratio had a negative impact on the vaccine response. Cytomegalovirus seropositivity had no apparent effect on HI titres before or after vaccination. Conclusions It is concluded that both pre-existing HI antibodies and previous vaccinations to influenza may influence the humoral response to influenza vaccination and that a CD4/CD8 ratio < 1 may indicate an impaired ability to respond to repeated antigenic stimulation.
Acknowledgements
We are grateful to Annette Nilsson Bowers, Marianne Morken and Remilyn Ramos-Ocao for excellent technical support.
Disclosure statement
All co-authors declare no commercial relationship or potential conflict interest related to the submission.
Funding information
This study was supported by grants from FUTURUM – The Academy for Healthcare, Region Jönköping County and FORSS – Medical Research Council of Southeast Sweden. The funders had no role in study design, data collection and interpretation or the decision to submit the work for publication.