Another terrible idea brought to you by the people who passed on purchasing several hundred million more doses of Pfizer’s A+ vaccine when offered the chance and still haven’t been able to explain why.

I doubt Trump bears any blame for either decision. Given his disinterest in policy detail, it’s hard to imagine him giving specific orders on vaccine procurement or distribution. Both of these cases were probably instances of his health-care bureaucrats telling him “here’s what we want to do” and him saying “fine, whatever you think is best.”

Which makes it that much worse. Experts are supposed to know what they’re doing. Why don’t they?

A top federal vaccine official said Wednesday that 2.9 million doses of Pfizer’s Covid-19 vaccine will be shipped around the country in the first week after it is authorized by the Food and Drug Administration — half of the initial shipment from Pfizer.

On a call with reporters, Gen. Gustave F. Perna, the chief operating officer for Operation Warp Speed, the federal effort to speed a vaccine to market, said that 2.9 million doses would be sent out once the vaccine is authorized, and 2.9 million saved for booster shots, which are given three weeks later. The remaining 500,000 of an available 6.4 million doses are to be held in reserve, in case they are unexpectedly needed.

That would make sense *if* it were true that someone receiving the first dose of the vaccine has zero immunity from the virus until they receive the second dose. In that case there’d be logic to making sure 2.9 million people are fully vaccinated, especially if we’re worried that supply-chain problems and manufacturing delays will make the second dose hard to come by for awhile. Once they’re immunized, that’s 2.9 million people who can no longer spread the virus to others — we hope. (Pfizer’s not sure yet whether people who’ve been vaccinated can still be infectious.)

But it’s not true. On the contrary, Pfizer’s own data suggests that the first dose alone provides quite a lot of immunity:

Pfizer reports “52.4% efficacy” for single dose but that includes the first seven days, before things kick in, when most new infections happened. At 10-12 days, the chart (eyeballing, no underlying data yet) looks ~80-85% efficacy. Unpleasant trade-off but reality is unpleasant.

— zeynep tufekci (@zeynep) December 10, 2020

If you can produce 80 percent immunity in 5.8 million people, hopefully rendering them incapable of transmitting the disease in the process, obviously that’s a better outcome than full immunity in just 2.9 million people at a moment when you’re desperate to slow down community spread. Even if vaccinated people remain infectious after contracting the virus, it might be that 80 percent immunity is enough to reduce some of the load on hospitals by turning cases that would have otherwise been severe into mild ones.

Former FDA chief Scott Gottlieb also favors partial immunity for the many over full immunity for a few as a means of pandemic control, going so far as to say that he’d use the entire first batch of vaccines stretching into January for first doses only. Get as many people partially immunized as you can and then hope and trust that Pfizer’s and Moderna’s manufacturing capacity catches up.

“We should get as many shots in our arms as possible right away,” he told the USA TODAY Editorial Board on Monday. “The idea that we need to cut (the doses) in half and give half of it now and hold onto it, so we have supply in January to get the second dose … I just fundamentally disagree with that.”

As the U.S. continues to suffer from a surge with nearly 200,000 new cases each day, according to a USA TODAY analysis of Johns Hopkins data, Gottlieb says the government should focus on vaccinating as many people as possible with first doses. He anticipates another 40 million doses should be ready in time for the second shot of the two-dose regimen.

The counterargument is that there’s a risk that the second doses won’t be available in three or four weeks’ time, which means people who got the first dose would end up as guinea pigs in an impromptu experiment to see what happens when you go longer than a month between doses. Is there any realistic likelihood of adverse side effects from that, though? The chief risk, one would think, would be that their immunity would fall off a bit by the time they finally got the second dose, possibly requiring them to get a third dose in order to be fully immunized.

Seems like a risk worth taking with 3,000 people dying every day without the vaccine, though. How many of those 3,000 who died yesterday would be alive if they’d had 80 percent immunity against the virus when they were infected?

Besides, we’re already out on a limb in managing the vaccine timetable. Despite the feds’ assurances that everyone who wants a vaccine by May will be able to get one, the number of doses on order from Moderna and Pfizer will only cover 100 million people. To get the rest of the population immunized in a timely manner will require approval of vaccines from other manufacturers that are still in trials, and it’s an open question right now whether any will meet the safety and efficacy benchmarks. If not, we’re staring at a shortage. The man who’ll inherit this problem six weeks from now promised a few days ago that 100 million doses would be distributed within the first 100 days of his administration, which would mean 50 million people fully vaccinated by April 30. That’d be nice, but that’s just 15 percent of the population. Assuming another 15 percent have natural immunity by that point, we’d still have a ways to go before herd immunity set in.

Moderna might come to the rescue on a looming vaccine shortage, though:

Existing U.S. deals with Pfizer and Moderna for 100 million doses of each company’s vaccine are only enough to inoculate a maximum of 100 million people combined. But earlier this year, Moderna said the U.S. has the option to buy 400 million more doses at a fixed price of $16.50 per shot…

“The U.S. Supply Agreement provides the U.S. Government with four additional and separate options to purchase 100 million doses per option of mRNA-1273,” Moderna said in the filing earlier this year. “Each option is exercisable at the sole discretion of the U.S. Government,” at various times during the first half of 2021.

Half a billion doses from Moderna plus 100 million from Pfizer would cover nearly the entire U.S. population, and since some Americans are destined to refuse the vaccine, it would almost certainly ensure that everyone who wants the shot will get one soonish. The question is purely whether Moderna can hit its goal of producing 500 million to one billion doses next year and how quickly. Either way, it’s a no-brainer that the feds should exercise their option and make sure those extra 400 million doses are on order, just in case. But that’s not to say that Moderna will be their best choice when all of the vaccine data is in: Remember that Johnson & Johnson is testing a one-dose vaccine that can be produced a bit more easily than Pfizer’s and Moderna’s products can. If the efficacy data confirms that that’s another A+ inoculation, it’ll be a godsend in terms of fully immunizing millions of recipients in much less time than the competition. That’s the only reason I can think of for why the feds might not want to go all-in on Pfizer and Moderna. Maybe they’re hoping to go all-in on J&J instead. Fingers crossed that they have reason to.