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Researchers say exercise can help the immune response in older adults after a flu vaccine. The Good Brigade/Getty Images
  • In a new study, researchers say exercise before and after a flu vaccination can boost a person’s immune response.
  • They say the benefits are particularly noticeable in older adults.
  • However, some experts caution against physical activity when you are feeling sick.

A new study out of Australia and the United Kingdom reports that exercise can boost a person’s immune response after they get a flu shot.

However, the benefits seem to be more pronounced in those who already exercise or exercise “acutely.” The benefits also appear to help older adults more than other age groups

Antibody response was measured before vaccination, immediately after vaccination, and at 4 to 6 weeks after vaccination, the time for peak antibody development.

Researchers examined data from six databases and two clinical registries. They identified nine studies, seven of which they used. In all, they examined data from 550 participants.

“Clinical measures of antibody response tended to be higher in the acute-exercised participants compared to rested controls and physically active compared to inactive,” the study authors wrote.

The periods of exercise comprised 15 to 50 minutes of resistance work or aerobic exercise. Most participants were monitored immediately before vaccination and immediately after.

Three potential moderators were included in the model: sex, body mass index (BMI), and age.

“Sex had no effect on outcomes for any strain. BMI had no effect on H1 or B strains, but in the H3 strain increasing BMI predicted smaller change in the titer,” the study authors said.

“Improved response with [physical activity] is more consistently identified among older populations. This suggests the young have the ability to respond well to vaccination regardless of sufficient (physical activity),” they added.

The study authors concluded: “Though we found some benefit from either acute exercise or [physical activity] on antibody titer levels, our finding did not support our hypothesis: there was no added benefit of acute exercise to inactive participants. Our findings point to new directions for exploration as subset analysis suggests acute exercise-PA interaction effects on immune response may be more pronounced in older populations. Such investigation has potential to identify means of improving antibody response for vaccines, particularly those for diseases which disproportionately affect older persons.”

Experts told Healthline the study results weren’t surprising.

“We know there are a myriad of health benefits to exercise. It is well established that exercise boosts the immune system, so this study makes perfect sense and fits into the existing body of knowledge,” said Dr. Alex McDonald, a family physician based in San Bernardino, California, and an expert on infectious diseases and sports medicine.

“It depends on the patient and their symptoms,” McDonald told Healthline. “There is a simple rule that I recommend to patients called ‘check the neck.’

“If a patient has called symptoms above the neck like a stuffy nose, headache, congestion, or a mild cough, then light aerobic exercise is recommended, since it may help boost the immune system and lessen symptoms,” he explained. “However, if a patient has symptoms below the neck such as body aches, fevers, chest congestion, or a deep cough this often indicates a more severe illness and exercise is not recommended as this may prolong recovery.”

McDonald said the optimal amount of exercise after vaccination depends on the person and their normal activity level.

“I generally recommend patients spend 50 percent of the time exercising at 50 percent the intensity they typically exercise at,” McDonald said. “For example, if someone usually walks 30 minutes at a brisk pace, I recommend 15 minutes at a slow pace. Alternatively, if a patient normally [does] strength training at the gym, I recommend half the weight and half the reps they normally engage.”

Dr. David Culpepper, the clinical director of telehealth company LifeMD, told Healthline exercise helps blood flow, which is important after receiving a vaccine.

“It seems logical to me that exercise after a flu shot would help circulate the vaccine throughout the body, thereby increasing the immune system’s response,” Culpepper said. “Since exercise increases the body’s metabolism, this can increase immune function as well.”

“However, I would use caution before exercising when sick, as your body might need its energy to recover. If you have a mild cold, however, I could see how some mild exercise could be beneficial, as long as you listen to your body when you get tired,” he added.

“For the average person, I would say about 20 to 40 minutes of cardiovascular exercise could be enough to increase circulation and improve your immune system’s response to the vaccine,” Culpepper said. “Though the research focused on the flu vaccine, it stands to reason that exercise would have the same beneficial effect for any vaccine. As vaccines can have varying side effects, I would advise you to check with your doctor just to make sure there is no specific caution against exercising after receiving a particular vaccine.”

Dr. Charles Bailey, medical director for infection prevention at Providence St. Joseph and Providence Mission Hospitals in Orange County, California, was skeptical.

He told Healthline the study was limited. He added it’s important not to send a message that exercising while ill is a good idea.

“While regular exercise while well does improve general health, including the immune system, exercising while ill wouldn’t be something I, or most clinicians, would recommend,” he said.

Dr. Natasha Trentacosta, a pediatric and adult sports medicine specialist and orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, told Healthline it comes down to what we already know about exercise boosting the immune system. Especially for older people.

“The healthier we are, the better we will be at combatting viral and bacterial infections that may enter the body,” Trentacosta said. “This is especially true as we age because the immune system’s responsiveness becomes reduced as we get older. As has been evidenced by our annual flu season and the COVID-19 epidemic, older people are more susceptible to contracting it due to underlying health conditions and weakened immune systems.”

“Improved circulation allows the cells and substances of the immune system to flow efficiently throughout the body, helping the immune system do its job most effectively and this study indicates that in tandem with the flu shot, there may be an added benefit,” Trentacosta added.