“Some individuals experience systemic symptoms post-vaccination, which overlap with COVID-19 symptoms,” wrote the researchers.
The study compared early post-vaccination symptoms in individuals who subsequently tested positive or negative for SARS-CoV-2 (the coronavirus that causes COVID-19), using data from the COVID Symptom Study app.
The COVID Symptom Study app has logged data on coronavirus symptoms, vaccination rates and side effects from over four million users throughout the pandemic.
The researchers compared participants who were asymptomatic when vaccinated with Pfizer-BioNTech vaccine or Oxford-AstraZeneca vaccine between 8 December 2020 and 17 May 2021, who subsequently reported symptoms within seven days (other than local symptoms at injection site) and were tested for SARS-CoV-2.
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