Fact check: COVID-19 vaccines did have clinical trials

Social media users have shared a video that falsely claims clinical trials for the COVID-19 vaccines did not take place.

Reuters Fact Check. REUTERS

The video features a conspiracy theorist who was banned from Facebook, YouTube and Twitter in 2020 for violating policies on misinformation (here , here).

The individual states: “What about the trials, that didn’t take place. Ladies and Gentlemen, the trial is the rolling out the vaccine fake. There were no trials, you’re the trial.” (here , 1:52). This is false.

The Oxford-AstraZeneca and Pfizer BioNTech vaccines, which are available in the UK, went through clinical trials (here) to prove their safety and efficacy. During the trials, half of the volunteers were given the vaccine and half were given a placebo dummy treatment (here).

Pfizer’s phase three clinical trial began in late July 2020 and the results were published in December 2020 (here). The trial enrolled 46,331 participants at 153 sites around the world in Argentina, Brazil, Turkey, South Africa and the United States, according to Pfizer’s website (here).

Oxford-AstraZeneca’s clinical trials involved 23,848 people across the UK, Brazil, and South Africa between April and November 2020, according to a report published by the Oxford Vaccine Group in the medical journal The Lancet (here , page 1).

A record of both trials can be viewed at, an online resource created by the US’ National Institutes of Health (here) and (here).

Reuters also reported on Pfizer and AstraZeneca’s clinical trials (here , here) and (here).

Clinical trials for other COVID-19 vaccines are ongoing, including those by Janssen (here) , Novavax (here) and Moderna (here).


False. Clinical trials for COVID-19 vaccines were carried out before they were approved by governments and rolled-out to the public. Pfizer’s trial enrolled over 45,000 participants across the globe and Oxford recruited over 23,000 people in the UK, Brazil, and South Africa.

This article was produced by the Reuters Fact Check team. Read more about our fact-checking work here.