Surprisingly simple way boost your flu shot's effectiveness

Unfortunately, getting a flu shot doesn’t absolutely guarantee that you’ll sail through flu season unaffected, or even that you’ll be safe from the specific flu strains contained in the shot. But there is one factor that might give you better odds: your mood.

A recent study recruited 138 adults aged 65 to 85, collecting data for two weeks before a flu shot about food and drink consumption, physical activity, stress levels, sleep, and having a positive or negative outlook. For a month after the shot, participants continued to track all of these factors.

Researchers found that only one of them was predictive of higher flu antibodies four weeks after the flu shot. They write in the study, “We found that greater positive mood, whether measured repeated over a 6-week period around vaccination, or on the day of vaccination, significantly predicted greater antibody responses to influenza vaccination.”

Previous studies have noted that chronic stress can negatively affect the immune response to vaccines, but this is the first one to look at whether lack of stress can have a positive impact, says Lisa Christian, PhD, at the Institute for Behavioral Medicine Research at Ohio State University Wexner Medical Center.

Having a sunnier outlook on life doesn’t just make you less likely to get the flu, either. Christian says research suggests that those with consistently low stress levels also have better health behaviors overall—they tend to exercise more, eat healthier foods, and sleep more soundly than their less-joyful peers.

“What we see is that the longer you maintain a positive mood, the better your health outcomes tend to be,” she says. “So, if you have that positivity for at least a few weeks before your flu shot, for example, you’ll likely be in a better position for that vaccine to work effectively.”

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This is especially important for seniors, she adds, since those over age 65 tend to have a poorer response to flu shots than kids, teens, or younger adults.

Don’t have weeks to turn your mood around? Even having a short-term feeling of uplift can be helpful, adds Loretta Graziano Breuning, PhD, author of Habits of a Happy Brain. That’s because a positive mood can decrease levels of cortisol, the hormone associated with the stressful “fight or flight” response.

When cortisol is high, she says, the body shuts down or depresses systems that aren’t necessary in an emergency, and that includes the immune system. But when that hormone decreases, others surge—such as dopamine, serotonin, and oxytocin—that support a healthy immune system.

“Even in the short term, this can have a beneficial effect,” says Breuning. “Your immune system will be stronger, and that can be helpful on the day you get your flu shot.”

This article first appeared on Prevention Magazine.