FRIDAY, April 30, 2021 (HealthDay News) — Systemic and local side effects to BNT162b2 and ChAdOx1 nCoV-19 vaccines occur at relatively low frequencies, according to a study published online April 27 in The Lancet Infectious Diseases.

Cristina Menni, Ph.D., from King’s College London, and colleagues conducted a prospective observational study to examine the proportion and probability of self-reported systemic and local side effects within eight days of vaccination among individuals receiving one or two doses of the BNT162b2 vaccine or one dose of the ChAdOx1 nCoV-19 vaccine.

A total of 627,383 individuals reported being vaccinated with 655,590 doses between Dec. 8, 2020, and March 10, 2021. The researchers found that systemic side effects were reported by 13.5 and 22.0 percent of individuals after the first and second doses of BNT162b2, respectively, and by 33.7 percent after their first dose of ChAdOx1 nCoV-19. Local side effects were reported by 71.9 and 68.5 percent after the first and second doses of BNT162b2, respectively, and by 58.7 percent after the first dose of ChAdOx1 nCoV-19. Compared with those without known past infection, systemic side effects were more common after the first BNT162b2 and ChAdOx1 nCoV-19 doses (1.6 and 2.9 times, respectively) among individuals with previous severe acute respiratory syndrome coronavirus 2 infection. Starting 12 days after the first dose, there was a significant reduction in the infection risk, reaching 60 percent for ChAdOx1 nCoV-19 and 69 and 72 percent for BNT162b2 at 21 to 44 and 45 to 59 days, respectively.

“Short-term adverse effects of both vaccines are moderate in frequency, mild in severity, and short-lived,” the authors write.

Several authors disclosed financial ties to pharmaceutical companies, including Pfizer and AstraZeneca, and to ZOE Global.

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