Pfizer and BioNTech’s Covid-19 vaccine candidate shows 90% efficacy, raising expectation for mRNA vaccines

Pfizer and BioNTech announced positive results from the interim analysis of their Covid-19 vaccine candidate BNT162b2, showing greater than 90% efficacy in 94 confirmed Covid-19 cases that occurred in Phase III trial participants without prior SARS-CoV-2 infection.

These results greatly exceed the 50% efficacy bar set by the US Food and Drug Administration (FDA). The announcement comes less than one year since SARS-CoV-2 was identified and seven months after the companies started their first Phase I study. More than 43,000 participants from diverse backgrounds were enrolled in the Phase III trial.

However, the 90% efficacy reported in the interim read-out can still decrease in the final analysis, which aims to include 164 cases of confirmed Covid-19.

Furthermore, important questions about how well the vaccine can prevent severe cases of Covid-19, its effect on carriage and transmission of the virus, and the long-term protection it offers will likely take many more months to be answered.

Pfizer and BioNTech will apply for Emergency Use Authorization once the FDA-required two month safety data are made available in the third week of November.

Experts initially assumed that the first iterations of a Covid-19 vaccine would show efficacies not much better than common seasonal influenza vaccines, which are usually only 40%–60% effective.

These results show that mRNA technology can be a powerful tool to quickly respond to emerging infectious disease threats. With a rising number of Covid-19 cases globally and the beginning of winter in North America and Europe, which is typically a higher-risk season for respiratory diseases, those hoping for a quick end to the pandemic will be excited by these new results.

Pfizer has said that 50 million vaccine doses will be available by the end of the year and 1.3 billion doses will be made available in 2021. However, concerns have been raised about the supply and distribution of Covid-19 vaccines, especially for mRNA vaccines that require deep-freeze storage and have a rather short shelf-life at refrigerator temperatures.

Dozens of other companies are also developing Covid-19 vaccines, and Phase III data are expected soon from AstraZeneca, Johnson & Johnson and Moderna, which is also developing an mRNA-based Covid-19 vaccine. Many manufacturing and supply deals have been made, and most of the companies have already started manufacturing ahead of Phase III results.

Having multiple vaccines available with even slightly lower efficacy would be immeasurably beneficial for controlling the outbreak, giving runway to ramping up manufacturing and bolstering distribution channels for more effective vaccines.

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