Don’t let the needle get you down. While a flu shot is not traditionally a time of unbridled joy, being in a good mood might actually help some people avoid influenza.

British researchers recently found that a positive mood in older adults when they received their flu shot appeared to bolster the response from their immune system, perhaps providing greater protection against the flu bug.

The study involved people age 65 or older. Researchers were unable to say whether this effect might be seen in other age groups, but their findings may open new lines of investigation to help boost the effectiveness of immunization for everyone.

The findings aren’t completely out of left field. Previous studies have suggested that mood can impact different aspects of our body’s immune response. For example, watching a comedy movie has been shown to increase antibodies in mucous secretions. Those antibodies play an important role in staving off harmful pathogens that can invade our mouths, lungs and gut, thus making us sick.

The mechanism of how exactly mood affects the immune system is still not clear, but researchers think stress hormones may be involved.

The British study tracked 138 people who were quizzed about their mood, stress, negative thoughts, diet and sleep patterns while their blood was tested for antibody response. All this took place in the weeks before and after the shot.

A good mood over the six-week observation period increased flu antibodies. But the effect was greatest if someone’s mood was positive the day of the shot.

More research is required, so don’t wait until you’re in a cheery mood to get your flu shot. But at least try to smile.