Vaccination, Strength & Fitness: What Does the Science Actually Say?

Over the last few years, few topics have generated more debate in gyms, sports clubs and fitness circles than vaccinations. Questions around whether vaccines reduce strength, impair recovery, or affect long-term fitness performance are common; particularly amongst people who train hard and value consistency.

As with most things in health and fitness, the truth sits somewhere between extremes.

The current body of peer-reviewed evidence suggests that vaccinations can produce short-term effects on training performance in some individuals, but there is no convincing evidence that vaccines cause long-term reductions in strength, cardiovascular fitness, muscle growth or athletic capability in healthy people. In fact, the opposite may often be true: by reducing the severity of infectious disease, vaccination may help preserve long-term health and training consistency. 

Short-Term Effects on Training Performance

Most vaccine side effects are temporary and related to the immune system doing exactly what it is designed to do, recognising a threat and preparing the body to respond.

Common short-term symptoms include:

• Fatigue

• Muscle soreness

• Mild fever

• Headaches

• Temporary reduction in energy output

For someone trying to hit a heavy deadlift session or perform high-intensity intervals, these symptoms can absolutely affect performance for 24–72 hours.

Research examining athletes and exercise immunology consistently shows that intense exercise performed immediately around vaccination may temporarily increase systemic stress and recovery demands. Several reviews recommend reducing training intensity for a short period following vaccination, particularly after COVID-19 or influenza vaccines. 

This is not unique to vaccination. The immune response itself requires energy and resources. If your body is mounting an immune response, it makes sense that maximal athletic output may temporarily decline.

In practice, most recreational lifters and athletes simply benefit from applying common sense:

• avoid maximal sessions immediately after vaccination,

• prioritise hydration and sleep,

• resume normal training once symptoms settle.

For most healthy individuals, this means little more than one or two slightly compromised training sessions.

What About Strength Loss or Muscle Wasting?

This is where misinformation often overtakes evidence.

There is currently no strong peer-reviewed evidence showing that routine vaccinations cause long-term muscle loss, reduced testosterone, impaired hypertrophy, or chronic reductions in strength performance in healthy individuals. 

What we do know is that actual viral illness can significantly impair training capacity for weeks or months.

Respiratory infections are associated with:

• reduced aerobic capacity,

• increased fatigue,

• muscle weakness,

• decreased training tolerance,

• prolonged recovery periods.

In some cases, viral infections can lead to myocarditis, chronic fatigue symptoms, or long-term reductions in exercise tolerance. Preventing severe illness therefore matters greatly for athletes and active adults alike. 

From a coaching perspective, missing two days of training due to vaccine fatigue is very different from losing six weeks of progression because of severe infection.

Vaccination and the Immune System in Athletes

Exercise itself has a complex relationship with immunity.

Moderate, consistent training appears to improve immune function and vaccine response, especially in older adults. Physically active individuals often demonstrate stronger antibody responses following vaccination than sedentary individuals. 

However, excessively intense training without adequate recovery may temporarily suppress certain aspects of immune function. This is one reason elite athletes are often advised to carefully manage training loads around vaccination periods. 

Again, context matters.

For the average person training 3–5 times per week, the evidence does not support fears of long-term performance decline from vaccination.

The Bigger Picture

Health and performance are built over years, not days.

The people who maintain strength, mobility and fitness into their 40s, 50s and beyond are rarely the ones chasing perfection, they are the ones staying healthy enough to train consistently.

Vaccination is ultimately a medical decision between an individual and their healthcare professional. But from a purely performance-based standpoint, the current scientific literature does not support the claim that vaccines cause lasting reductions in strength or fitness in healthy populations.

Temporary disruption? Possibly.

Permanent impairment? Current evidence says no.

And as always in fitness, consistency beats intensity over the long term.

Peer-Reviewed References

• Dinas PC et al. Effects of Exercise and Physical Activity Levels on Vaccination Efficacy: A Systematic Review. Medicina, 2022. 

• Agha-Alinejad H et al. A Guide to Different Intensities of Exercise, Vaccination, and Nutritional Strategies in Athletes During COVID-19. International Journal of Environmental Research and Public Health, 2022. 

• Barni L et al. Does Physical Exercise Enhance the Immune Response after Vaccination? Vaccines, 2023. 

• Ruuskanen O et al. Vaccinations for Elite Athletes. Vaccines, 2025. 

• Simpson RJ et al. Can Exercise Affect Immune Function to Increase Susceptibility to Infection? Exercise Immunology Review, 2020. 

• Campbell JP & Turner JE. Debunking the Myth of Exercise-Induced Immune Suppression. Frontiers in Immunology, 2018. 

• Edwards KM & Booy R. Effects of Exercise on Vaccine-Induced Immune Responses. Human Vaccines & Immunotherapeutics, 2013.