Could being in a positive mood predict flu vaccine effectiveness?

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Researchers from the University of Nottingham (UK) have reported that being in a positive mood on the day of influenza vaccination could help predict, and improve, its effectiveness.

Flu vaccination is estimated to be effective in only 17–53% of the elderly, compared with 70–90% of younger people. It has previously been demonstrated that patient psychological and behavioural factors can influence immunity, and consequently vaccination outcomes. However, the relative importance of the psycho-behavioral influences was unknown. This study, published recently in Brain, Behavior and Immunity, therefore hoped to understand which factors had the greatest impact on influenza vaccination.

The researchers enrolled a cohort of 138 individuals aged 65–85 years who were due for a flu jab, monitoring factors including mood, physical activity, sleep and diet three-times per week over a 6 week period – 2 weeks prior to vaccination and 4 weeks after. In addition, the team measured IgG responses at 4 and 16 weeks post-vaccination.

The group discovered that of all the factors monitored, only positive mood predicted vaccine effectiveness, observing that a good mood across the 6 week reporting period was associated with higher antibody levels. The researchers then assessed mood on the day of the vaccination itself, demonstrating an even greater effect, with a positive mood appearing to improve vaccine effectiveness, accounting for 8–14% if the variability in antibody levels.

Author, Kavita Vedhara (University of Nottingham), commented: “Vaccinations are an incredibly effective way of reducing the likelihood of catching infectious diseases. But their Achilles heel is that their ability to protect against disease is affected by how well an individual’s immune system works. So people with less effective immune systems, such as the elderly, may find vaccines don’t work as well for them as they do in the young.

“We have known for many years that a number of psychological and behavioural factors such as stress, physical activity and diet influence how well the immune system works and these factors have also been shown to influence how well vaccines protect against disease.”

Due to the flu vaccine in this study being the same composition as the previous year – a very unusual event – the researchers only focused on one of the viruses vaccinated against, which had the lowest antibody levels prior to vaccination, in their assessments. Although focusing on one strain isn’t an uncommon approach, the team state that in order to confirm these findings it would be best to assess psycho-behavioural influences in the context of a vaccination with more novel strains.

Sources: Ayling K, Fairclough L, Tighe P et al. Positive mood on the day of influenza vaccination predicts vaccine effectiveness: A prospective observational cohort study. Brain Behav. Immun. doi:10.1016/j.bbi.2017.09.008 (2017) (Epub ahead of print); https://www.eurekalert.org/pub_releases/2017-09/uon-sfb092517.php

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