Why Second Doses Of Covid-19 Coronavirus Vaccines May Have More Side Effects

Some people have reported experiencing more side effects when getting their second doses of the Moderna or Pfizer/BioNTech Covid-19 vaccine compared to when they got their first doses. For example, the COVID Symptom Study website states that “after effects are more common the second time around, with around one in five who received their second dose of the Pfizer vaccine logging at least one systemic effect.” Indeed, a December 31, 2020, publication in the New England Journal of Medicine had indicated that in the Phase 3 clinical trial of the Pfizer/BioNTech vaccine, side effects that involved more than just the injection site were reported “more often after dose 2 than dose 1.”