COVID-19: Are the Vaccines Safe?

Page updated on Mar 12, 2021 at 1:51 PM

Are COVID-19 Vaccines Safe?

473 - Why Should I Get the Vaccine? Factsheet Vaccine icons
  • Vaccines are one of the safest and most effective ways to save lives, protect your loved ones, and help everyone return to normal.
  • Every major medical study has shown that Pfizer and Moderna vaccines are safe and effective.
  • The Pfizer and Moderna vaccines are Food and Drug Administration (FDA) authorized, and passed clinical trials with more than 40,000 participants, with almost 40% of the study coming from diverse populations.
  • The vaccines were produced quickly, which makes some people nervous. Scientists have been studying coronaviruses for 50 years, and working on vaccines since the SARS epidemic in 2002.
  • Your chance of experiencing a severe reaction to the COVID-19 vaccine is very low, less than 1%. Talk to your doctor if you have a history of allergic reactions to medicines.
  • Mild side effects such as arm pain or temporary headache or fever are normal signs that your body is building protection against future infections. Most side effects go away in a few days.
  • Medical experts recommend pregnant and lactating women to receive the current COVID-19 vaccines when it is available for their priority group.

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How Were the COVID-19 Vaccines Developed and Proven to be Safe?

Clinical development for vaccines is a three-phase process. Learn more about the process at a glance 

  • During Phase I, small groups of people receive the trial vaccine to help determine safety and side effects.
  • In Phase II, the clinical study is expanded and the vaccine is given to people who have characteristics (such as age and physical health) similar to those for whom the new vaccine is intended. The purpose of Phase II is to identify the optimal dose and schedule of the vaccine and how it impacts various groups of the population. In the case of COVID-19 vaccines, Phase II trials in the U.S. should have a demographic makeup similar to that of the country, spanning a wide range of ages, races, ethnicities, and any other factors that would affect risk and efficacy.
  • In Phase III, the final formulation of the vaccine is given to thousands of people and tested for efficacy and safety. During clinical development, a trial vaccine’s effectiveness is determined by comparing outcomes of patients who have received it with outcomes of patients who received the placebo.

Vaccine Safety Steps

In the U.S., the findings from clinical trials are presented to and reviewed by the FDA. The FDA also inspects manufacturing facilities to ensure safety and reviews product labels to ensure clarity. After approving a vaccine, the FDA continues to monitor and oversee its production to ensure that all safety protocols are followed. In addition, many vaccines undergo Phase IV formal and ongoing studies after the vaccine is approved and licensed. The FDA and CDC also collect and analyze information from reports of any side effects that may occur after a vaccine has been licensed.

In summary, before a new vaccine is available to the public, it has been given to thousands of people under stringent monitoring for safety and effectiveness. Sometimes, very rare side effects are recognized only after the vaccine is licensed because they occur so infrequently, but such side effects are very rare and must be weighed against the benefits the vaccine will provide.