Study Shows a Positive Mood Could Boost Effectiveness of Flu Vaccine

Researchers at the University of Nottingham in England have found evidence that being in a positive mood when receiving an influenza (flu) vaccine can increase its protective effect. The study is the first to examine several psychological and behavioral factors that have been shown to affect how well vaccinations work. In this study, researchers investigated which factor or combination of factors has the greatest impact on the ability of the vaccinations to protect against disease. The investigators 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 adults due to have their flu vaccine. They then measured the amount of influenza antibody in the blood at four weeks and 16 weeks after vaccination. Results showed only positive mood over the six-week observational period was associated with higher levels of antibody. And, they found influences on the day of the vaccination had an even greater effect on how well it worked, accounting for between 8 percent and 14 percent of variability in antibody levels.

“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,” said professor Kavita Vedhara from the university’s division of primary care. “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, however, because participants received the identical flu vaccine that they had the previous year. Therefore, the researchers found 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. Because of this “ceiling effect,” antibody levels for these two viruses were unlikely to reveal effects of psychological and behavioral factors. As a result, the researchers focused only on the one strain that was the least immunogenic (i.e., the strain with the low levels of antibody prior to vaccination).