One Dose of Coronavirus Vaccine May Be Enough for Most People

A new analysis of Pfizer data suggests good protection starting 14 days after the first shot.

Data sleuths trolling through the FDA filings for the Pfizer and Moderna vaccines have uncovered, what they say, is a critical fact — these vaccines may be highly effective after just a single dose. Given that vaccine demand vastly outpaces supply, as well as the concern that more coronavirus variants will emerge if we don’t rapidly squelch the infection rate, calls for a one-shot-only approach abound.

Is that the right move? Well, like all things public health, it’s complicated.

But first let’s reconstruct what the researchers did.

If you dig a bit into Pfizer’s FDA filing, you’ll find this table, which breaks down the number of cases in the vaccine and placebo group from the very first dose.

You see 50 cases total in the vaccine group, and 275 in the placebo group, for 82% efficacy. Of course, we wouldn’t expect the vaccine to be effective the instant it is injected. That’s why the primary outcome looked at infection…