Psychological stress and antibody response to influenza vaccination: a meta-analysis.

Vaccination is an important public health strategy for reducing the risk of influenza at the societal level. However, at the individual level, not everyone is protected by vaccination, and increases in antibody titers may fail to reach protective levels. Several recent studies suggest that psychological stress may contribute to these individual differences. Exploring this hypothesis, we conducted a meta-analysis of 13 studies examining the influence of psychological stress on antibody responses following influenza vaccination. The studies were identified through systematic searches in MEDLINE and PsychINFO and included a total of 1158 men and women. In five studies, the increased antibody levels of caregivers following vaccination were compared to those of non-caregivers. The remaining studies focused on associations between self-reported stressful life events or perceived stress and increased antibody titers following vaccination. The meta-analysis revealed a significant negative association between psychological stress and antibody responses to influenza vaccination. While effect sizes were similar across different indicators of stress, antibody responses to the A/H1N1 and B-influenza types appeared to be more sensitive to stress than the A/H3N2 type. It was investigated whether the association between stress and antibody response differed between young and elderly, and the results revealed significant negative associations between stress and peak antibody titers in both age groups. These findings suggest the importance of additional research to explore responsible mechanisms and possible contributions of stress to the public health problem of inadequate responses to vaccination.