Interpretational considerations when using healthy individuals as a surrogate for elite athletes in response to vaccination.

to the editor: We read with interest the article, “Recent COVID-19 vaccination has minimal effects on the physiological responses to graded exercise in physically active healthy people” by Batatinha and colleagues (1). The authors compared physiological responses to standardized exercise in physically active, disease-free adults pre- and post-COVID-19 vaccination (Pfizer or Johnson and Johnson), and in an unvaccinated control group. We believe this study has great merit and applaud the authors’ creative thinking and quick action to investigate a novel scientific question pertinent to current public health. However, there are a few considerations that we believe are important when interpreting and making recommendations on the strength of the study’s findings. First, the study rationale was the reluctance of some elite athletes to receive a vaccination on account of the potential for future impaired physical performance. The study population may not have been representative of the specific rationale of the study or from which to formulate recommendations for elite athletes. For example, the mean predicted maximal oxygen uptake (V̇o2max) of the study population was 40.7 mL/kg/min and would be considered “Poor” according to the American College of Sports Medicine (ACSM). Furthermore, elite athletes have more robust immune responses compared with poorly conditioned individuals (2). A second consideration is the temporal distance (21 days) between the second dose of the vaccination and the postvaccination exercise tests. The authors mention athletes’ concern regarding proximity of vaccination to competition and loss of training days due to vaccination side effects. Elite athletes often train daily, thus understanding the potential impact of vaccination on physiological responses to exercise at different postvaccination time points is important to exercise/training prescription. Finally, the authors report an increase in heart rate (HR) without a change in stroke volume or cardiac output in response to vaccination. These data seem incompatible as an increase in HR without a decrease in stroke volume would necessarily increase cardiac output. However, it is possible that the study was not sufficiently powered or the methods the authors used were not sensitive enough to detect a change in stroke volume or cardiac output. We agree with the authors that true tests of performance (such as time trials) in elite athletes warrant future study, and we also suggest that a future study incorporate varying temporal proximities to the vaccination such that athletes will have a greater appreciation for performance changes relative to the date of vaccination.

DISCLOSURES

No conflicts of interest, financial or otherwise, are declared by the authors.

AUTHOR CONTRIBUTIONS

T.R.E. drafted manuscript; T.R.E. and K.S.S.A. edited and revised manuscript; T.R.E. and K.S.S.A. approved final version of manuscript.