To determine whether depressed or anxious patients experience greater affective change than mentally healthy individuals following influenza vaccination.

Participants (n=112) completed the Positive and Negative Affect Schedule (PANAS) before influenza vaccination and 1–2days post-vaccination (M=32.3h). Pre- and post-vaccination PANAS scores were compared using two-tailed, paired-samples t-tests. Change in positive affect between participants with depression or anxiety and those without was compared using two-way ANOVA. Follow up positive affect was further examined using multiple linear regression.

Positive affect decreased following vaccination (M=2.18, 95% CI [1.07, 3.29], t(111)=3.89, p<0.001) for all participants and was more pronounced for those with anxiety or depression (F(1, 110)=7.51, p=0.009). Similarly, predicted follow up affect score was higher for those without a mental health conditions (β=3.67, 95% CI [1.18, 6.16], t(103)=2.92, p=0.004).

These data suggest that influenza vaccine has a greater effect on affect in patients with depression and anxiety than in mentally healthy individuals. This effect was focused on positive affect, suggesting that influenza vaccine induced inflammation may be best suited to examine alterations in positive affect and positive valence systems.