Studies have found convincing evidence that regular exercise can prevent the more serious consequences of infection with SARS-CoV-2, the virus that causes COVID-19. Physical activity reduces the risk of hospitalization, need for ventilation and death.

Physical activity does more than this, however. A South African study has found it also ratchets up the effectiveness of the COVID-19 vaccine, helping prevent serious outcomes. Fully vaccinated people who got the most exercise were almost three times less likely to need to be hospitalized for COVID-19 compared to those were vaccinated but who got the least exercise. Those who got some exercise were 1.5 times less likely to be hospitalized.

The findings may inform recommendations for physical activity, particularly for people who are immunocompromised and at greater risk for serious outcomes from COVID-19, such as those with comorbidities and older persons. “Public health messaging should encourage physical activity as a simple, cost-effective way of enhancing vaccine effectiveness to mitigate the risk of severe COVID-19 requiring hospitalization,” the researchers said.

Fully vaccinated people who got the most exercise were almost three times less likely to need to be hospitalized for COVID-19 compared to those were vaccinated but who got the least exercise.

The study relied on data collected from almost 200,000 adults who were enrolled in the Discovery Health insurance plan and the Vitality healthy lifestyle program, using participants’ anonymized medical records and readings from wearable activity trackers.

People in the study were placed in three subgroups based on their exercise intensity: those who got low levels of physical activity (less than 60 minutes per week); moderate levels of activity (60 to 149 minutes per week); and high levels of activity (150 minutes or more per week).

Vaccinated participants had received a single dose of the Johnson and Johnson vaccine against SARS-CoV-2 more than 28 days prior to enrollment. All the vaccinated participants were healthcare workers, while the unvaccinated control group included all Discovery Health members, not just healthcare workers.

All participants were followed for over three months. During this period, participants who were fully vaccinated and had high levels of physical activity had an 86 percent lower risk of hospitalization with COVID-19 during this time than those who were unvaccinated; those who got medium levels of levels of activity had a 72 percent lower risk; and those who got low levels of physical activity had a 60 percent lower risk.

How physical activity boosts vaccine effectiveness is not yet known. The researchers believe it may involve increased antibody levels, enhanced T-cell activity and psychosocial factors. Mitochondria, the powerhouses of cells, may also play an important role. Physical activity helps protect and repair mitochondria, and promotes the development of new mitochondria.

The researchers point out that this was an observational study and so cannot establish a cause and effect relationship between physical activity levels and the risk of COVID-19 hospitalization. The results also might not be applicable to other populations, SARS-CoV-2 variants such as Omicron and other types of COVID-19 vaccines, such as the mRNA vaccines from Pfizer/Bio-N-Tech and Moderna.

Future studies might look at the effect of activity on waning vaccine effectiveness, as well as the effect of an additional dose of the Johnson and Johnson vaccine, which is now a standard recommendation.

The study was published in the British Journal of Sports Medicine.