In a new study, European scientists found evidence that being in a positive mood on the day of a flu vaccination can increase its protective effect.
Investigators from the University of Nottingham said their study is the first to examine several psychological and behavioral factors that have been shown to affect how well vaccinations work.
The researchers set out to understand which factor, or combination of factors has the greatest impact on the ability of vaccinations to protect against disease. Study results appear in the journal Brain, Behavior and Immunity.
The findings are important as flu vaccinations are estimated to only be effective in 17-53 percent of older adults compared to 70-90 percent of younger people. With the onset of winter and flu season, the research is likely to be of interest to anyone having their autumn immunizations.
The investigative team measured negative mood, positive mood, physical activity, diet, and sleep three times a week over a six week period in a group of 138 older people due to have their flu shot. Then they examined how well the inoculation was working by measuring the amount of influenza antibody in the blood at four weeks and 16 weeks after the vaccination.
The results showed that of all of the factors measured, only positive mood over the six week observational period predicted how well the jab worked, with good mood associated with higher levels of antibody.
In fact, when the researchers looked at influences on the day of vaccination itself, they found an even greater effect on how well it worked, accounting for between eight and 14 percent of the variability in antibody levels.
Professor Kavita Vedhara, from the University’s Division of Primary Care, said, “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 behavioral 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.”
The study was unusual in that, by chance, the vaccination that participants received was identical to the one they had received in the previous year. This has happened only once before since the turn of the century. As a result, the researchers found that participants had very high levels of antibody — and therefore protection — for two out of three of the viruses present in the vaccination, even before they were vaccinated.
This so-called “ceiling effect” meant that this study was unlikely to see further large increases in antibody levels for these two viruses and therefore was unlikely to reveal an effect of psychological and behavioral factors. As a result, the team focused its analyses on the one strain which was the least “immunogenic;” i.e., the strain with low levels of antibody prior to vaccination.
The researchers said focusing on individual viral strains is not uncommon, but recommended that future research would be best conducted in the context of a vaccination with more novel viral strains to further confirm the positive mood effect on vaccination.