The researchers speculate that the athletes’ immune systems had been strengthened and fine-tuned by the daily physical demands and damages of training, allowing them to respond so effectively to the vaccine.
But those results, while notable, did not look at the acute effects of exercise and whether a single, intense workout might alter the body’s reactions to a vaccine, for better or worse. So, for the second of the new studies, which was published in July in Medicine & Science in Sports & Exercise, the scientists returned to the same data, but focused now only on the immune reactions of the athletes.
They compared the numbers of immune cells and antibodies in those athletes who happened to have gotten their flu shot within two hours of their most recent training session against those of athletes whose shot had come a day after their last workout. If intense training blunted immune reactions, then the first group of athletes would be expected to show fewer new immune cells than those who had gotten their shot after a longer rest.
But the researchers found no differences. Whether the athletes’ inoculations came almost immediately after training or a day later, their immune reactions were the same. A strenuous workout beforehand had not lowered — or boosted — the response.
Together, the two studies tell us that being in shape is likely to increase our protection from a vaccination, no matter how intensely or when we work out before the shot, Dr. Sester says.
Of course, these studies focused on elite, competitive athletes, which most of us are not. But Dr. Sester believes even more-casual recreational athletes are likely to mount better flu-vaccine responses than sedentary people. Likewise, she and her colleagues expect high fitness should improve immune responses to other vaccines, including, potentially, a Covid-19 shot.
“The basic principles of vaccine response are probably the same,” she says. Future studies will have to confirm that possibility, though, if and when a vaccine becomes available.