* A study was conducted in South Africa to test the hypothesis that exercise improves the effectiveness of COVID vaccination.
* The study used data for approximately 200,000 PCR tests where the vaccination status and exercise levels of the people tested were known.
* Only approximately 5% of people were vaccinated in the study. This is vastly different to vaccination rates in the rest of the English speaking world.
* The vaccinated people were all healthcare workers. Unvaccinated individuals included both health care workers and non-healthcare workers. This introduced important confounders, which were not adjusted for. Ethnicity and other important factors were also not adjusted for.
* The main claim was "Vaccine effectiveness against a COVID-19-related admission among vaccinated individuals within the low activity group was 60.0%, 72.1% for the moderate activity group, and 85.8% for the high activity group."
* The secondary claim was "physical activity enhances vaccine effectiveness."
* I found support for the main claim, but not the secondary one. However, there were many issues with the paper, which undermined the robustness of these findings.
* An interesting, and unexpected, finding was that there appeared to be a 'sweet spot' for vaccination. There were lower levels of hospitalisation among people defined as fully vaccinated (28 or more days after vaccination). The highest level of hospitalisation was in the first few days, post vaccination. This should have been highlighted, for people to be able to make informed choices about medical interventions.
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