How Coronavirus Vaccine Side Effects Will Be Tracked in the U.S.

It looks increasingly likely that a COVID-19 vaccine may be approved in the coming weeks, with pharmaceutical companies Pfizer and Moderna both seeking Emergency Use Authorizations from the U.S. Food and Drug Administration (FDA).

Even after approval—if it comes—government agencies and manufacturers will keep a close eye on the safety of these products as they are administered to the public.

Regulators will only approve a vaccine if results from large Phase III clinical trials demonstrate that it is sufficiently safe and effective. This applies even in a public health emergency such as the COVID pandemic.

But these Phase III trials, which often involve tens of thousands of people, do not always uncover every potential side effect of a vaccine, so close scrutiny will continue.

"Once the vaccine is made available to the public, reports from health care professionals and from patients about side effects are monitored daily. Each safety or side effect report is reviewed individually as well as cumulatively with all other side effect reports, also employing advanced computer methods to identify safety signals for a product," said Dr. Craig Hartford, from the Faculty of Pharmaceutical Medicine in London.

In the United States, the Department of Health and Human Services has several ways to monitor and investigate adverse reactions to medicines.

One vaccine surveillance system, which has been jointly run by the Centers for Disease Control and Prevention and the FDA since 1990, is called the Vaccine Adverse Event Reporting System (VAERS.)

"VAERS takes reports of any adverse event a person experiences around the time of receiving a vaccine or that they think might be related to the vaccine. Anyone can report to VAERS—the vaccinated person, parents of vaccinated children, health care providers," Lisa Lee, a public health expert at Virginia Tech, told Newsweek.

The CDC has developed a second surveillance system, an app called V-SAFE. This will send a text or email at regular intervals to people who receive a COVID-19 vaccine, asking them questions about their health.

If a person reports that they have felt sick, missed work, been unable to carry out normal activities or received medical are, a VAERS expert will contact them to learn more.

"Monitoring adverse events is critical for all drugs and vaccines. Clinical trials are very useful for assessing safety and efficacy of a vaccine, but sometimes people will report things we did not observe in a trial," Lee said.

"One reason to monitor and follow up on reports of adverse events is to see if others have also experienced them, or to rule out that they are related to the vaccine. We all have a vested interest in ensuring the safest and most effective vaccines and long-term monitoring helps us do that."

Approved vaccines can have side effects, but these are unusual, typically mild and wear off within days, according to Hartford.

"Serious side effects are rare," he said. "The benefits of the vaccine outweigh the risks and the safety of vaccines is very closely monitored and assessed."