Early Phase III data show Pfizer, BioNTech's COVID-19 vaccine over 90% effective

Results from the first interim analysis of a Phase III study of Pfizer and BioNTech's BNT162b2 showed that the experimental mRNA-based vaccine candidate was more than 90% effective in preventing COVID-19 in participants without evidence of prior SARS-CoV-2 infection, the companies announced Monday. The data "provides the initial evidence of our vaccine's ability to prevent COVID-19," remarked Pfizer CEO Albert Bourla, adding "I think we can see light at the end of the tunnel."

The study began in July and has enrolled 43,538 participants to date, 38,955 of whom have received a second dose of the vaccine candidate as of November 8. Pfizer and BioNTech noted that while the original interim analysis was scheduled to be conducted after 32 confirmed cases of COVID-19 in trial participants, this was increased to a minimum of 62 cases following discussions with the FDA. The companies added that upon conclusion of the talks, the evaluable case count had reached 94 and the independent data monitoring committee (DMC) performed its first analysis on all cases on November 8.

Effectiveness tops expectations

According to the analysis, the case split between vaccinated individuals and those who received the placebo indicates a vaccine efficacy rate above 90% at seven days after the second dose. The drugmakers noted that the results mean that protection is achieved 28 days after the initiation of the vaccination, which consists of a two-dose schedule, although as the study continues, the final vaccine efficacy percentage may vary.

With effectiveness for the first vaccines against COVID-19 previously expected to be in the range of 60% to 70%, "more than 90% is extraordinary," remarked BioNTech chief executive Ugur Sahin. "It shows that COVID-19 can be controlled," Sahin said, adding "at the end of the day, it's really a victory of science." For further analysis, read ViewPoints: It works! – Pfizer, BioNTech deliver a COVID-19 vaccine breakthrough.

Safety data continue to accumulate

Pfizer and BioNTech said the DMC has not reported any serious safety concerns and recommends that the study continue as planned. Last month, Bourla reiterated that Pfizer would not apply for FDA emergency-use authorisation (EUA) for BNT162b2 until a key safety milestone is met, which is expected to be in the third week of November. Under recent guidance, the FDA requires that companies provide two months of safety data on half of trial participants following the final dose of a potential COVID-19 vaccine.

William Gruber, Pfizer's senior vice president for vaccine clinical R&D, remarked that the vaccine's efficacy was better than even the best result he had hoped for. However, he cautioned that it is not yet known how well BNT162b2 works in certain subgroups, such as the elderly, as these analyses have yet to be conducted. It also remains unknown whether the vaccine prevents severe disease, as none of the participants who got COVID-19 in the interim analysis had severe cases, Gruber explained. In addition, Bourla said "how long this protection lasts is something we don't know."

New secondary endpoints

Meanwhile, the study will continue through to its final analysis at 164 confirmed cases, while participants will continue to be monitored for long-term protection and safety for an additional two years after the second dose. Pfizer and BioNTech added that the trial will also evaluate the potential for BNT162b2to provide protection against COVID-19 in those who have had prior exposure to SARS-CoV-2, as well as vaccine prevention against severe COVID-19 disease.

In addition to the primary efficacy endpoints, the companies noted that the final analysis will now include new secondary outcome measures evaluating efficacy based on cases accruing 14 days after the second dose as well. Pfizer and BioNTech explained that these additional secondary goals, which have been agreed with the FDA, "will help align data across all COVID-19 vaccine studies and allow for cross-trial learnings and comparisons between different vaccine platforms."

Periodical vaccinations likely

"What we know right now -- it is with very, very high level of confidence these are very highly effective vaccines. What we know so far, it means that we don't have any safety concerns, but we need to wait until the results are there," Bourla remarked. The chief executive noted that although it's not yet known whether the COVID-19 vaccine will become a yearly or seasonal immunisation, "I think it is a likely scenario that you will need periodical vaccinations." Bourla explained "the reason why we selected the RNA technology was exactly that. This is a technology that you can boost without problems of creating antibodies against your vaccine, again and again and again."

Pfizer and BioNTech said that they currently expect to produce up to 50 million doses of BNT162b2 this year, rising to up to 1.3 billion doses in 2021. "Who will get this vaccine? We have two separate manufacturing lines. One is in the US. Those we prefer using mainly for Americans," Bourla commented, adding that the second line in Europe will be used to produce vaccines for the rest of the world.

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