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kottke.org posts about Pfizer

Initial Data Shows Covid-19 Vaccine Is More than 90% Effective

posted by Jason Kottke   Nov 09, 2020

In a press release (and not a paper in a peer-reviewed journal) based on a preliminary outside review of data from its phase 3 trial, Pfizer says its Covid-19 vaccine was more than 90% effective in preventing the disease.

The company said that the analysis found that the vaccine was more than 90 percent effective in preventing the disease among trial volunteers who had no evidence of prior coronavirus infection. If the results hold up, that level of protection would put it on par with highly effective childhood vaccines for diseases such as measles. No serious safety concerns have been observed, the company said.

I really hope this analysis holds up when more data from the study is released:

The data released by Pfizer Monday was delivered in a news release, not a peer-reviewed medical journal. It is not conclusive evidence that the vaccine is safe and effective, and the initial finding of more than 90 percent efficacy could change as the trial goes on.

The world, and the United States, could really really use some good news like this about the pandemic.

Update: Here’s Pfizer’s press release. And a thread from Dr. Natalie Dean on how she is interpreting this news (“Celebrate, but let the process play out over time as intended.”)

Pfizer’s first analysis was planned for 32 events, which they pushed back after discussions with FDA. But by the time they analyzed the data, 94 had accrued. This shows how quickly trials can generate results when placed in hotspots (and how much transmission is ongoing!).

These vaccines are tested until a certain number of infections happen. So you have this interesting paradoxical situation where if a potential vaccine is more successful at curbing infection, the longer it takes for the study to conclude. You get a better vaccine but wait longer for it. Countering that are the rising transmission counts in the US — more community transmission will get you to the target number of infections more quickly.

Update: From virologist Dr. Florian Krammer, a thread about what Pfizer and other companies will be looking for in terms of the efficacy of vaccines in a number of different situations. Overall, he is optimistic about these preliminary results. And here’s a FAQ about the vaccine from the NY Times.

Another open question is whether children will get protection from the vaccine. The trial run by Pfizer and BioNTech initially was open to people 18 or older, but in September they began including teenagers as young as 16. Last month, they launched a new trial on children as young as 12 and plan to work their way to younger ages.

Update: A very simplified explanation of Pfizer’s RNA-based vaccine.