Effect of BNT162b2 mRNA booster vaccination on VO(2) (max) in recreational athletes: A prospective cohort study

BACKGROUND AND AIMS: The goal of the present study was to systematically evaluate the effect of a booster vaccination with the BNT162b2 messenger RNA (mRNA; Pfizer‐BioNTech®) vaccine on maximum oxygen uptake (VO(2) (max)), potential signs of (peri)myocarditis, and sports participation. METHODS: Recreational athletes who were scheduled to undergo booster vaccination were evaluated with transthoracic echocardiography, serum measurements of high‐sensitivity C‐reactive protein(hsCRP) and high‐sensitivity troponin I, and a bicycle cardiopulmonary exercise test (CPET) with serum lactate evaluation before the booster vaccine administration. Seven days postvaccination the test battery was repeated. Additionally, the subjects were asked to fill in a questionnaire on side effects and a subjective evaluation of their relative training volume and intensity as compared to the weeks before vaccination. RESULTS: A group of 42 analysed athletes showed a statistically significant 2.7% decrease in VO(2) (max) after vaccination (mean standard error of mean pre: 48.6 (1.4) ml/kg/min; post: 47.3 (1.4) ml/kg/min; p = 0.004). A potentially clinically relevant decrease of 8.6% or more occurred in 8 (19%) athletes. Other CPET parameters and lactate curves were comparable. We found no serological or echocardiographic evidence of (peri)myocarditis. A slight but significant increase in hsCRP was noted 1 week after vaccination. Side effects were mild and sports participation was generally unchanged or mildly decreased after vaccination. CONCLUSION: In our population of recreational endurance athletes, booster vaccination with the BNT162b2 mRNA vaccine resulted in a statistically significant decrease in VO(2max) 7 days after vaccination. The clinical impact hereof needs to be further determined. No major adverse events were observed.