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I'm thinking more about the Pfizer vaccine (and grateful for those who have clarified some key points). First, I agree that early efficacy (right after the second injection) prevents infection in this patient population. That seems statistically certain.
Second, the population is those the investigator deems to be at high risk. I know that we've all wanted "wiggle room" in our inclusion criteria and that's not wrong. But for generalizability we want to know what "high risk" really means. In the event, it looks like "high-risk"
meant ~40/10,000 in the placebo group got COVID in the first month, versus ~4/10,000 (having to estimate because not enough detail in the news release). Note that (contra some bizarre innumeracy in Vox), this doesn't mean it fully protects 9 out of every 10 people who receive it
but rather that, on average, your baseline risk of getting COVID drops by 90% 28 days after receiving the vaccine. Whether the vaccine has the same effect in people with extremely high risk (e.g. family members of a patient) is not yet known, but bear in mind that it probably
takes >2-3 weeks to work (assumption in the trial is 4 weeks), so it probably won't work as post-exposure prophylaxis. Biggest "bang for the buck" will likely be in nursing home residents and people who are incarcerated, where its effect may more than anything be to limit
big outbreaks. And, of course, the end game with any vaccine for this awful virus is to interrupt the pandemic, and a vaccine effectiveness of 90% is fabulously promising.
Third, I understand better their decision to continue enrolling because efficacy is only one piece of a vaccine, especially a vaccine based on fairly new technology. We really do need to know if there are safety risks that outweigh the benefits of the vaccine. It doesn't take
many cases of encephalitis or other auto-immune disease (or, heaven forbid, antibody-dependent enhancement) to invalidate even a 90% effective vaccine in this patient population. So we need to know. I also salute their decision to gather more data to make their results more
comparable to other current trials, since we're going to need a suite of vaccines to get through this. So let's look forward to the results from the safety checks and further efficacy experience after we have wrapped up our Zoom Thanksgiving.
And of course for now we need stricter physical distancing measures, universal masking, and steep restrictions on customer density and flow through restaurants, bars, gyms, etc. And no live parties or extended family dinners.
