Days are getting shorter and evenings cooler in temperate regions. With the onset of winter and the “flu season,” the research is likely to be of interest to people who are having their flu shot. The annual flu vaccine is the best way to reduce your risk of getting sick with seasonal flu and spreading it to others. The flu vaccine is not 100 percent effective ― not only because of the differences in virus strains attacking us, but also based on the person getting the shot and whether they develop a strong protective immune response.
This study conducted by University of Nottingham experts is the first to look into several psychological and behavioral factors that have been shown to have an effect on the effectiveness of vaccinations. The study investigators aimed to identify which factor, or combination of factors, has the greatest impact on the ability of vaccines to protect against disease.
The team measured positive mood, physical activity, diet, stress, negative thoughts, sleep patterns, and other measures of psychological and physical health, three times a week over a six-week period in a group of 138 older people due to have their flu shot. Then, the amount of influenza antibody in the blood was measured at four weeks and 16 weeks to examine how well the flu shot was working.
The results showed that of all of the factors measured, only positive mood, whether measured repeatedly over a six-week period around vaccination, or on the day of vaccination, was associated with higher blood levels of antibodies to H1N1, a potentially dangerous flu strain, at both four and 16 weeks post-vaccination. When the researchers looked at influences on the day of vaccination, they found an even greater effect on how well it worked, accounting for between 8 and 14 percent of the variability in antibody levels.
According to Professor Kavita Vedhara, from the University’s Division of Primary Care:
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 that 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.
Flu viruses are constantly changing, thus the flu strains in the vaccine is reviewed each year and updated as needed based on which flu viruses are circulating, making people sick, and how well the flu strains in the previous season’s vaccine protects against those viruses.
The study was unusual in that the flu strains in the vaccine that participants received was identical to the one they had received in the previous year. As a result, the researchers found that participants had very high levels of antibody ––two out of three flu strains were present in the vaccine given in the previous year.
This so-called “ceiling effect” meant that this study was unlikely to see further significant 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 say that the approach of focusing on individual viral strains is not uncommon, but recommend that future research is best conducted in the context of a vaccination with more novel viral strains to further confirm the positive mood effect on vaccination. This is certainly a fascinating finding, and these surprising results could really help researchers looking for new ways to boost the efficacy of the seasonal flu vaccine. The investigators acknowledge they were unable to control for all possible variables, and that their observational study does not prove cause and effect. The investigators now plan to conduct clinical trials, to attempt to show whether good mood definitely cause flu vaccines to work better in older people.
Nevertheless, be happy; feel good — it might make your flu shot more effective.