Human factors and vaccine responses: how behaviours impact reactogenicity and immunogenicity

A healthy lifestyle can optimize immune system function, but its ability to benefit vaccine responses is less established. The effects of external factors, such as weather, which influence our health behaviours are also less clear. This thesis investigated whether there is an interaction effect from acute exercise and physical activity (PA) on antibody responses; whether adverse events following immunization (AEFI) vary with time or weather; and whether lifestyle behaviours affect the likelihood of AEFI or post-vaccination disease incidence. Study one evaluated the interaction effect on antibody responses in individual participant data (n = 550) from a meta-analysis. Study two examined associations between ambient temperature and AEFI using a large active surveillance dataset; study three similarly evaluated the time of day and AEFI relationship. Study four examined associations between behaviours and vaccine effectiveness and reactogenicity in a 16-week study of 1301 participants. Some health behaviours were associated with vaccine immunogenicity but had minimal associations with reactogenicity. Sufficient PA increased the likelihood for seroconversion. Usual sleep quality was inversely associated with illness; other associations included a sex × age interaction, indicating the higher illness frequency in women dissipated with age, and a positive association between AEFI and illness. In contrast, the only behaviour associated with AEFI was usual sleep duration. AEFI were also associated with vaccine coadministration and showed a sex × age interaction, with increased AEFI in females relative to males from 7.5-87.5 years of age. The thesis demonstrated that health behaviours can affect vaccine responses. Future research with objective measures addressing the roles of PA and sleep in immunogenic responses would improve understanding and potentially provide avenues for improving vaccination effectiveness and experience