Updated data show 91% efficacy for Pfizer, BioNTech COVID-19 vaccine at six months

Pfizer and BioNTech on Thursday said updated topline results from a pivotal Phase III study of their COVID-19 vaccine BNT162b2 show it was 91.3% effective at preventing the disease up to six months after the second dose. The new analysis of 46,307 participants in the trial is based on 927 confirmed symptomatic cases of COVID-19 observed through March 13, with 850 cases reported in the placebo group and 77 among those who received BNT162b2.

In terms of severe disease, the companies said there were 32 cases as defined by the US Centers for Disease Control and Prevention, all in the placebo group, for an efficacy rate of 100% against severe illness. When looking at severe COVID-19 as defined by the FDA, there were 21 cases in the study's placebo arm versus one in the BNT162b2 vaccinated group, translating to 95.3% effectiveness. "Efficacy was generally consistent across age, gender, race and ethnicity demographics, and across participants with a variety of underlying conditions," the companies said.

Early signs of efficacy against B.1.351

Moreover, Pfizer and BioNTech noted that BNT162b2 was 100% effective at preventing COVID-19 cases among trial participants in South Africa, where the B.1.351 lineage is prevalent. They said that among the 800 study participants enrolled in the country, nine cases of COVID-19 were observed, all in the placebo group. In an exploratory analysis, the nine strains were sequenced and six of them were confirmed to be of the B.1.351 lineage. The companies said that while the vaccine had induced a lower antibody response to the B1.351 variant in recent laboratory studies than against the original SARS-CoV-2 strain, "it does not appear to affect the high observed efficacy against [the South African] variant."

Ugur Sahin, CEO of BioNTech, stated the updated findings "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." Meanwhile, a total of 697 cases of COVID-19 were observed among trial participants in the US, including 647 cases in the placebo group and 50 among vaccinated individuals, for an efficacy rate of 92.6%.

The companies also said BNT162b2 continues to have a favourable safety and tolerability profile, based on pivotal trial data now collected from more than 12,000 vaccinated participants followed-up for at least six months after the second dose. The companies say they plan to submit detailed results for scientific peer review and potential publication in the near future.

Enough data to seek full FDA approval

A previous analysis of the pivotal trial released last November had shown BNT162b2 to be 95% effective at seven days after the second dose, calculated based on 170 cases of COVID-19. Those findings have been used to support emergency authorisations of the mRNA-based vaccine for people 16 years and older in multiple markets, including the UKUS and EU. However, these latest results "position us to submit a [full] biologics license application to the FDA," remarked Pfizer CEO Albert Bourla.

Earlier this week, the companies reported the first results from a Phase III study testing BNT162b2 in younger adolescents, saying the vaccine was safe and 100% effective in those aged 12 to 15 years old, based on 18 cases of COVID-19, all of which were in the placebo arm. Pfizer and BioNTech indicated they plan to seek authorisation of the vaccine for this age group as well. Meanwhile, new real-world data from a small study in the UK also showed high immune responses among people ages 80 to 96 years who received two doses of the vaccine three weeks apart. Those findings have not yet been peer-reviewed.

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