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

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 ), potential signs of (peri)myocarditis, and sports participation. 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. A group of 42 analysed athletes showed a statistically significant 2.7% decrease in VO after vaccination (mean standard error of mean pre: 48.6 (1.4) ml/kg/min; post: 47.3 (1.4) ml/kg/min; = 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. In our population of recreational endurance athletes, booster vaccination with the BNT162b2 mRNA vaccine resulted in a statistically significant decrease in VO 7 days after vaccination. The clinical impact hereof needs to be further determined. No major adverse events were observed.