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Are COVID-19 vaccines safe and effective? How were they tested and approved?

Last Updated: 04/04/2022

COVID-19 vaccines are safe and effective.

Millions of people in the United States have received COVID-19 vaccines since they were authorized for emergency use by FDA. These vaccines have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.

COVID-19 vaccination reduces the risk of COVID-19 and its potentially severe complications. All COVID-19 vaccines currently approved or authorized for use in the United States helped protect people against COVID-19, including severe illness, in clinical trial settings.

Compared to fully vaccinated people, recent studies have shown that unvaccinated people have:

  • 6.1x greater risk of testing positive for COVID-19
  • 11.3x greater risk of dying from COVID-19

Are COVID-19 vaccines safe even though they were developed rapidly?

The vaccines were able to be developed rapidly because of the following:

  • Vaccines have already been created for coronaviruses similar to SARS-CoV-2 (the virus that causes COVID-19), so a lot of the work was already done.
  • All vaccines have gone through the same steps to show safety and effectiveness.
  • Many steps occurred at the same time (e.g., vaccines were being made while testing was taking place). No steps were skipped.
  • Collaboration between medical experts and researchers, along with plentiful funding helped to bring vaccines to the public sooner

COVID-19 vaccines are safe and effective. Millions of people in the United States have received COVID-19 vaccines since they were approved or authorized for emergency use by FDA. These vaccines have undergone and will continue to undergo the most intensive safety monitoring in U.S. history.

What vaccines are approved or authorized for use?

The following are the COVID-19 vaccines available in the United States

  • Pfizer/BioNTech/ Comirnaty
  • Moderna
  • Johnson & Johnson's Janssen

Everyone 6 months or older is eligible for a COVID-19 vaccine in New Jersey and encouraged to get vaccinated as soon as possible. Learn more.

Everyone 5 and older should get a booster shot – if it has been at least 5 months (3 months for immunocompromised children and adults) after your primary Pfizer or Moderna series, or at least 2 months after your one dose J&J shot. At this time, only the Pfizer vaccine is authorized and recommended for children aged 5 through 17. Learn more.

For more information, visit the CDC's webpages on:

For FDA fact sheets for authorized vaccines, visit the FDA's "COVID-19 Vaccines" page. For additional resources in over a dozen languages, visit the FDA's multilingual COVID-19 resources page.

Side Effects

After receiving an injection of a COVID-19 vaccine, you will be observed for 15 minutes by healthcare staff to monitor any side effects. Observation may be longer (30 minutes) if you have a history of anaphylaxis (severe allergic reaction).

Like many vaccines, a COVID-19 vaccine may cause some temporary discomfort. In addition to a sore arm, side effects of the vaccines may include tiredness, headache, muscle pain, chills, joint pain, fever, injection site swelling, injection site redness, nausea, feeling unwell, and swollen lymph nodes.

There is a small chance that vaccines could cause a severe allergic reaction. A severe allergic reaction would usually occur within a few minutes to one hour, which is why all individuals should be observed for at least 15 minutes after vaccination and 30 minutes if they have a history of a severe allergic reaction due to any cause.

There is a remote chance that the Johnson & Johnson vaccine could increase risk of blood clots with low levels of platelets. Nearly all reports have been in adult women younger than 50 years old. After a temporary pause in the use of the Johnson & Johnson vaccine, the FDA and CDC determined that the vaccine's known and potential benefits outweigh its known and potential risks and recommended use of the Johnson & Johnson vaccine resume.

There have been reports of cases of inflammation of the heart – called myocarditis and pericarditis – happening after mRNA COVID-19 vaccination (Pfizer and Moderna). In most cases, patients have responded well to medications and rest and had prompt improvement of symptoms. Reported cases have occurred predominantly in male adolescents and young adults 16 years of age and older. The CDC continues to recommend COVID-19 vaccination for everyone 12 years of age and older given the greater risk of other serious complications related to COVID-19.

The CDC and FDA are monitoring rare reports of Guillain-Barré syndrome (GBS) after the Johnson & Johnson vaccine. The majority of cases have occurred in males aged 50 and older about two weeks after vaccination, mostly within six weeks.

For more information on vaccine safety, visit https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html and speak with your healthcare provider.

Source: https://www.state.nj.us/health/cd/documents/topics/NCOV/Public_FAQ.pdf; https:/www.cdc.gov/coronavirus/2019-ncov/vaccines/safety.html; https://www.fda.gov/coronavirus-disease-2019-covid-19/covid-19-vaccines