A Feasibility Trial of a Brief Positive Affect Intervention to Improve the Effectiveness of Influenza Vaccine Response in Older Adults.

The Centers for Disease Control (CDC) describe vaccinations as among the 10 most significant health achievements ever documented; and for many conditions they have been an unmitigated success (e.g., smallpox). There are, however, several populations in whom vaccine effectiveness is far from optimal. These populations are typically contending with underlying immune impairment by virtue of their advancing age and/or the presence of co-existing diseases (e.g., cancer). As a consequence, vaccines are most likely to fail those whom they most seek to benefit: individuals at the greatest risk of ill health.

This has prompted research into treatments that enhance immune function prior to vaccination, so called vaccine adjuvants. The aim of such treatments is to optimise the response the immune system makes to the vaccine antigens and, in so doing, increase the likelihood that the vaccine confers protection.

One area in which there has been interest is in the potential for developing psycho-behavioural vaccine adjuvants. There is considerable evidence that psychological and behavioural factors can modulate immunity; with diet, physical activity, stress, affect, sleep and social support all associated with immune response.

The investigators recently conducted a longitudinal observational cohort study of multiple psychological (positive affect, negative affect, stress) and behavioural (physical activity, sleep, diet) influences on short and long-term antibody responses to influenza vaccination in older adults. This identified positive affect as the most influential psycho-behavioural factor on influenza-specific antibody responses, independently predicting both short and long-term antibody responses in the weakest immunogenic strain above and beyond known demographic and clinical determinants. Intriguingly, the investigators also observed preliminary evidence that positive affect on the day of vaccination was more predictive of antibody responses following vaccination than mood measured over the longer period surrounding vaccination. As influenza-specific antibodies are a well-established correlate of protection from serologically and clinically diagnosed influenza incidence, these data suggest that increasing positive affect immediately prior to vaccination could be used as a non-pharmacological vaccine adjuvant.

Through a series of systematic steps, including focus groups and interviews with older adults and health care professionals, the investigators have recently developed a brief, positive affect intervention - designed to improve short-term mood in older adults and be deliverable within primary care. It is hoped this could act as a psycho-behavioural adjuvant to enhance poor responses to influenza vaccination in older adults. Before performing a definitive trial of the intervention's effectiveness, a feasibility trial is needed for number of reasons: