Vaccines are an important preventive measure against influenza, but they are often much less effective in the elderly. A new study suggests that seniors who get their flu shots while in a good mood have a better response to the vaccine.

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Researchers suggest that positive moods may have something to do with how effective flu vaccines are in seniors.

Flu vaccines are an easy and important preventive measure against seasonal influenza viruses. Many, if not most, of us choose to go through the mild and short-lived discomfort of getting a flu shot each year so that we may avoid coming to more grief later.

The most recent data provided by the Centers for Disease Control and Prevention (CDC) show that vaccination reduces the risk of catching the virus by 40 to 60 percent among the general United States population.

Overall, however, the vaccines tend to be more effective for children, teenagers, and adults up to 65 years of age. Seniors, studies suggest, tend to have a poorer response, and the vaccines are not always effective in keeping the illness at bay.

Still, the CDC urge adults aged 65 and over to keep getting their flu shots, since influenza viruses can have much more serious effects on seniors, possibly leading to hospitalization and a higher mortality risk.

Now, a study conducted by researchers based at Nottingham University in the United Kingdom looks at why vaccines may be more effective for some older adults, but not for others.

Prof. Kavita Vedhara and colleagues noted that the vaccine was more effective in seniors who turned up for their flu shot in a good mood, but less so in their unenthusiastic counterparts.

“Vaccinations are an incredibly effective way of reducing the likelihood of catching infectious diseases,” explains Prof. Vedhara. “But their Achilles heel is that their ability to protect against disease is affected by how well an individual’s immune system works.

“So,” she adds, “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.”

This is why she and her team decided to investigate which additional factors may be responsible for good – or poor – outcomes following vaccination in the elderly. The researchers published their findings in the journal Brain, Behavior, and Immunity.

Prof. Kavita Vedhara and team worked with 138 people aged between 65 and 85 who were due to get vaccinated for influenza. The participants were followed over 6 weeks and monitored for mood, dietary practice, physical activity, and sleep patterns three times each week.

The researchers then tested the effectiveness of the flu shot at 4 weeks and 16 weeks after inoculation, by testing the levels of antibodies in the participants’ blood.

Of all the factors monitored, it was found that positive mood was the best predictor of effectiveness. Participants who were in a good mood on the day of the vaccination itself exhibited an even better response to the flu shot, and the inoculation was significantly more effective for this group of people.

Good mood, the scientists explain, was responsible for between 8 and 14 percent of the difference in antibody levels between participants.

“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,” says Prof. Vedhara, “and these factors have also been shown to influence how well vaccines protect against disease.”

Now, it has become apparent just how much psychological factors could influence the “receptiveness” of the immune system.

One peculiarity of this study, the team explains, is that the vaccine administered to the participants was the same as the one they had received the previous year. The paper indicates that everyone “received a standard dose of the 2014/15 northern hemisphere influenza vaccine.”

This is an extremely rare occurrence, yet it meant that the subjects already had high antibody levels for two of the three viruses contained by the vaccine: the A H3N2 and B viral strains.

As a consequence, Prof. Vedhara and colleagues focused on the response to the third viral strain, A H1N1, to which the participants had not previously developed significant antibody levels.

The researchers emphasize in their paper that this study is the first of its kind, shedding additional light on the factors at play in the context of vaccine effectiveness in old age.

Despite these limitations, this is the first study to comprehensively examine patient behaviors and psychological factors on the vaccine-induced protective antibody response in older adults using a robust methodology.”

Prof. Vedhara and her research team hope that future studies will test the influence of the factors they monitored on multiple viral strains, to confirm the effect of mood on vaccine efficacy in the elderly.