Fact check: It is standard practice for vaccine safety monitoring to continue after approval

Social media users have asked why clinical trials for COVID-19 vaccines are set to continue for several years if the jab is safe.

Reuters Fact Check. REUTERS

Examples can be seen (here) and (here).

“COVID-19 vaccine trials are ongoing. What does that mean for those taking the vaccine?”, one post shared on Facebook asks.

The post correctly notes that the Pfizer-BioNTech coronavirus vaccine has been given an “estimated study completion date” of Jan. 31, 2023 (here). For the COVID-19 vaccine created by Moderna, studies are expected to end on Oct. 27, 2022 (here).

However, it is standard practice for safety monitoring to continue after a vaccine has been approved for use.

After clearing final Phase III clinical trials, the Pfizer-BioNTech vaccine was granted approval for emergency use by U.S. regulators in December 2020 (here).

Pfizer reported that it would continue safety monitoring of participants in its Phase III trial. (here).

This means that “all trial participants will continue to be monitored to assess long-term protection and safety for an additional two years after their second dose” (here).

Similarly, Moderna said that it would continue to follow participants from its Phase III trial for the next two years (here).

Additional data collected will include “longer term safety follow-up, duration of protection against COVID-19, and efficacy against asymptomatic SARS-CoV-2 infection”.

How vaccinates are tested, licensed and monitored for safety is explained by Oxford University’s Vaccine Knowledge Project (here).

Vaccines are also monitored by government bodies as they are rolled out, with the UK using the Yellow Card scheme (here) and the U.S. government operating VAERS (

Although the vaccines have completed the necessary steps of each trial, the health and economic impact of COVID-19 has meant the process has been sped up.

There has been a global effort to pool resources in order to accelerate the development and production of vaccines (here).

On top of this, unprecedented financial investments and scientific collaborations have made it possible for some steps in research and development to happen “in parallel” (here).

For example, some clinical trials are evaluating multiple vaccines at the same time, though clinical and safety standards are maintained despite the acceleration.


Missing context. It is standard procedure for safety monitoring to continue after vaccines have been approved for use.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here .