Soon we’ll find out whether vaccine holdouts meant it when they said they didn’t want the shot because it’s “experimental.”

That’ll no longer be true as of Monday. A new excuse for not getting immunized will need to be found.

Then again, given the cascade of employer mandates this is likely to trigger, some holdouts will have their arms twisted into getting vaccinated whether they feel reassured by the announcement or not.

The Food and Drug Administration is pushing to approve Pfizer-BioNTech’s two-dose Covid-19 vaccine on Monday, further expediting an earlier timeline for licensing the shot, according to people familiar with the agency’s planning.

Regulators were working to finish the process by Friday but were still working through a substantial amount of paperwork and negotiation with the company. The people familiar with the planning, who were not authorized to speak publicly about it, cautioned that the approval might slide beyond Monday if some components of the review need more time…

The approval is expected to pave the way for a series of vaccination requirements by public and private organizations who were awaiting firmer regulatory backing before implementing mandates. Federal and state health officials are also hoping that an approved vaccine will draw interest from some Americans who have been hesitant to take one that was only authorized for emergency use, a phenomenon suggested by recent polling.

I’ve seen at least three segments on Fox News this week celebrating antibody treatments for those who’ve already been infected with COVID, each of which has insinuated that they’re an alternative to vaccination. (They aren’t.) It’ll be interesting to see if the wider availability of those treatments becomes a new excuse for vaccine resisters not to get their shots.

If so, it’ll be ironic since antibody treatments remain under emergency-use authorization. Come Monday, they’ll be the “experimental” option, not the vaccine.

There’s good news on vaccinations, by the way. For the first time since June 30-July 1, the U.S. has topped a million doses on consecutive days:

There’s no mystery behind what’s responsible for that upward trend. Exactly one month ago, the seven-day daily average bottomed out at 507,000 doses per day. Coincidentally, that was around the time that the threat from a hyper-contagious new variant began penetrating the public consciousness. By July 27, the CDC had revised its mask guidance to recommend masking indoors even for vaccinated people in the name of containing Delta. Obviously, anxiety about the variant and the daily barrage of warnings that getting immunized is an insurance policy against being hospitalized has knocked some fencesitters into the pro-vax camp over the past month.

The mandates that will follow full authorization next month will knock more.

Boosters are coming too beginning next month. There’s good news there as well, via Israel:

Israel is reporting a 4-fold increase in protection from infection after a 3rd booster shot, compared to an age-gender matched cohort of 2 doses

And 5-6 fold increased protection from hospitalization and severe disease

3rd dose now approved for all, tomorrow starting in 40+ y/o pic.twitter.com/NpSRVhyKu7

— Eran Segal (@segal_eran) August 19, 2021

The first group of Israelis to receive boosters were age ≥60. The impact is apparent with divergence of the curves. https://t.co/PcbFJpgJaH pic.twitter.com/cRd6pdajmR

— Eric Topol (@EricTopol) August 20, 2021

There’s some anxiety among the feds that authorizing a third shot for the vaccinated while they’re busy trying to convince the unvaccinated to get their first will discourage the latter by leading them to believe they’re signing up for an endless series of shots. But the fact that Israel is experiencing a nasty wave from Delta in tandem with the data showing waning immunity in older people over time evidently convinced the CDC that they can’t wait. To protect the country this fall they need to run on parallel tracks and try to get shots into the vaccinated and the unvaccinated.

Which brings us to a mystery. Why is Israel enduring a major wave of COVID when the UK’s experience with Delta has been more mild? They have similar shares of their respective populations vaccinated and they’re battling the same variant. The disparity in outcomes is leading scientists like Scott Gottlieb to wonder if it has to do with the different timing used by the two countries in dispensing doses. I wondered about that myself in a post last week:

The time between the first and second doses of Pfizer is typically three weeks; the time between the first and second doses of Moderna is four weeks. Does that extra week matter? Maybe. A UK study published last month found that delaying the second dose induces the body to generate more antibodies once that dose is finally given. The “sweet spot” for Pfizer against Delta, according to the researchers, was eight weeks between doses, not three. Maybe having to wait an extra week for their second dose was a blessing in disguise for Moderna recipients, boosting their immune system meaningfully beyond what a three-week interim would have.

And maybe the UK finding explains why that country has done so much better with its summer Delta wave than we have. Remember that the UK followed a “first doses first” strategy that ignored the recommended three-week interval for Pfizer doses. The British government believed they’d slow the spread of the virus more efficiently by generating partial immunity in a large share of the population than by generating full immunity in a smaller share. The available vaccine supply was used to give everyone a first dose and only once that was done, months later, did second doses start going out. That had two benefits. By delaying the second dose, the Brits got closer to the immunity interval “sweet spot” than we did. And by giving out many of their second doses later in the year than we in the U.S. did, they fortuitously boosted the immunity of a huge share of their population right before Delta arrived.

A new report from the UK provides further evidence: “COVID vaccines were more effective against symptomatic disease with at least six weeks between doses than with only three to four weeks between doses.” Like us, however, Israel followed the dosing schedule recommended by Pfizer, dishing out the second dose after only three weeks. Pfizer used that schedule for testing because we were in the middle of a pandemic and they needed to know ASAP if the vaccine was effective. Three weeks wasn’t necessarily the optimal interval, just an interval which they were confident would show whether the shots were working or not. Spacing them out longer might have created more durable immunity here — and may very well have done so in the UK, which could explain why their Delta wave has been gentler than Israel’s and ours.

I’ll leave you with Gottlieb, who’s also intrigued by the possibility. If a long duration between doses is the key to building lasting immunity then you can see why a booster after eight months has some scientists convinced that we won’t need a fourth shot for a long time, if ever.

When it comes to predicting new cases and hospitalization rates from the Delta variant, should the U.S. take its cues from developments out of the UK or Israel? @scottgottliebmd weighs in. pic.twitter.com/1OtkrYliw5

— CNBC's Closing Bell (@CNBCClosingBell) August 20, 2021