Pfizer and BioNTech have announced that their Covid-19 vaccine BNT162b2 is 91.3% effective against Covid-19, measured seven days through up to six months after the second dose.

The updated top-line results are based on the analysis of 927 confirmed symptomatic Covid-19 cases in the phase 3 clinical trials, who were followed till 13 March 2021.

BNT162b2 was 100% effective against severe Covid-19, as defined by the US Centres for Disease Control and Prevention (CDC), and 95.3% effective against severe Covid-19 as defined by the US Food and Drug Administration (FDA).

Pfizer chairman and chief executive officer Albert Bourla said: “These data confirm the favourable efficacy and safety profile of our vaccine and position us to submit a Biologics License Application to the U.S. FDA.

“The high vaccine efficacy observed through up to six months following a second dose and against the variant prevalent in South Africa provides further confidence in our vaccine’s overall effectiveness.”

Pfizer and BioNTech said that the updated analysis of the Phase 3 clinical trial is in accordance with the FDA guidance for companies investigating Covid-19 vaccines.

Results from the analysis of 46,307 trial participants confirms the previous data and shows strong protection against Covid-19 through six months post-second dose.

The vaccine showed a favourable safety and tolerability profile, based on safety data from more than 12,000 participants vaccinated in the phase 3 trial.

Also, the vaccine efficacy was generally consistent across age, gender, race and ethnicity demographics, and across participants with a variety of underlying conditions.

In the phase 3 trials, a total of 697 Covid-19 cases were observed in the US, with 647 in the placebo group compared to 50 in the vaccine group, indicating vaccine efficacy of 92.6%.

In South Africa, where the B.1.351 variant is prevalent, 800 participants were enrolled in the study, and nine cases of Covid-19 were observed, all in the placebo group.

Jointly developed by BioNTech and Pfizer, BNT162b2 has not been approved or licensed by the US FDA, but was granted an Emergency Use Authorization (EUA), for active immunisation in people aged 16 years and above.

BioNTech CEO and co-founder Ugur Sahin said: “It is an important step to further confirm the strong efficacy and good safety data we have seen so far, especially in a longer-term follow-up.

“These data also provide the first clinical results that a vaccine can effectively protect against currently circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population.”

Furthermore, Pfizer and BioNTech have commenced a Phase 1/2/3 trial to evaluate the safety, tolerability, and immunogenicity of their Covid-19 vaccine in children, aged below 12 years.