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Vaccine side effects

Vaccine side effects, such as anaphylaxis and myocarditis, are rare and usually treatable, with public health guidance emphasizing preparedness and monitoring.

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Jan 15, 2026
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How do booster doses of Pfizer and Moderna affect the frequency and severity of side effects compared with the primary series?

Booster doses of the mRNA COVID-19 vaccines tend to cause local and systemic reactions that are generally similar in type but not more severe than reactions seen after the primary series, with most tr...