Biden receives another negative Covid-19 test after close contact with positive staffer

Most people who have been vaccinated against Covid-19 experience some side effects, but most are mild or very mild, and serious adverse effects are rare, according to a study published Wednesday in the medical journal JAMA Open Network.

After receiving a second dose of the Pfizer/BioNTech or Moderna vaccine or one dose of the Johnson & Johnson vaccine, about 80% of people reported some side effects – the most common being fatigue, muscle pain, headache and chills. But only 0.2% of people reported experiencing an allergic reaction or anaphylaxis after full vaccination – a total of 27 people out of more than 11,000 responses.

For this study, researchers from the University of California, San Francisco, conducted daily, weekly and monthly surveys about health and Covid-19-related events among an online cohort of adults between March 26 and May 19, 2021. The survey included nearly 20,000 participants, though not all participants responded to all questions. 

The study also found that there was a “strong association” to adverse reactions to the Covid-19 vaccine among those who reported being infected with Covid-19 prior to being vaccinated.

People who received the Moderna vaccine were about twice as likely to report experiencing side effects than those who received the Pfizer/BioNTech vaccine, as were women. Those who received the J&J vaccine had lower odds of adverse effects, along older people and those with asthma.

More on the study: The researchers note that while the surveyed group was diverse, rural residents and people reporting lower subjective social status are underrepresented. Also, not all participants responded to all surveys, which may affect results.