Some individuals experience side effects to the COVID-19 vaccine including mild to moderate headache, fever, and fatigue that resolves within a day or two. Side effects were more common after the second dose of the mRNA vaccines compared to the first. Side effects after the single Johnson & Johnson shot were similar to those seen after dose 2 of the mRNA vaccines. Side effects from the COVID booster shots are similar to those experienced following the initial vaccine series, and often milder.
In clinical trials for children, side effects were similar to those seen in adults and older children but less severe. The most common side effects reported included pain at the injection site, fatigue, headache, and muscle pain. No serious side effects including myocarditis (inflammation of the heart tissue) were seen in clinical trials of children ages 6 months and older.
Rare cases of myocarditis, or inflammation of the heart muscle, were seen in a very small number of teens and young adults after receiving an mRNA vaccine (Moderna or Pfizer). The vast majority of these cases were seen in males after the second dose and were mild. Myocarditis can also result from COVID infection. After careful review, the FDA determined that the benefits of vaccination against COVID infection outweigh the extremely rare risk of myocarditis.
Following approval of the Johnson and Johnson vaccine, very rare but serious blood clots were observed, mostly in women under the age of 50. For this reason, the CDC recommends mRNA vaccines (Pfizer or Moderna) when available. Individuals who received Johnson and Johnson originally should receive an mRNA booster. No increased risk of blood clots have been observed for the mRNA vaccines.
After you are fully vaccinated there is still a low risk that you may become infected and spread COVID-19. For this reason, it is still important for you to take steps to prevent the spread of COVID-19. Get more information from the CDC about what you can do safely after you are vaccinated.