Developing COVID-19 Vaccines

New vaccines are first developed in laboratories. Scientists have been working for many years to develop vaccines against coronaviruses, such as those that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). SARS-CoV-2, the virus that causes COVID-19, is related to these other coronaviruses. The knowledge that was gained through past research on coronavirus vaccines helped speed up the initial development of the current COVID-19 vaccines.

Before vaccines are made available to people in real-world settings, FDA assesses the findings from clinical trials.  Initially, they determined that three COVID-19 vaccines met FDA’s safety and effectiveness standards and granted those vaccines Emergency Use Authorizations (EUAs)external icon. The EUAs allowed the vaccines to be quickly distributed for use while maintaining the same high safety standards required for all vaccines. Learn more in this video about EUAs.

FDA has now granted full approval for Pfizer-BioNTech (COMIRNATY) COVID-19 Vaccineexternal icon for people ages 16 years and older and for Moderna (Spikevax) COVID-19 Vaccine for people ages 18 years and older.  Before granting approval, FDA reviewed evidence that built on the data and information submitted to support the EUA. This included preclinical and clinical trial data and information, as well as details of the manufacturing process, vaccine testing results to ensure vaccine quality, and inspections of the sites where the vaccine is made. These vaccines were found to meet the high standards for safety, effectiveness, and manufacturing quality FDA requires of an approved product. Learn more about the process for FDA approvalexternal icon.

As vaccines are distributed outside of clinical trials, several monitoring systems continue to track them to ensure their safety. Hundreds of millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring in U.S. history. Some people have no side effects. Many people have reported common side effects after COVID-19 vaccination, like pain or swelling at the injection site, a headache, chills, or fever. These reactions are common and are normal signs that your body is building protection.

Reports of serious adverse events after vaccination are rare. CDC and FDA continue to closely monitor several reporting systems, like the Vaccine Adverse Event Reporting System (VAERS), Vaccine Safety Datalink (VSD), and v-safe, which help look for safety issues now that the vaccines are being given to patients in real-world settings across the country. CDC provides timely updates on selected serious adverse events reported after COVID-19 vaccination.