Delta’s surging and antibodies are waning: What to know about when we’ll need COVID-19 booster shots

• Should the US start offering people an extra COVID-19 vaccines dose?
• Supporters cite signs of waning protection and data suggesting a booster shot would help.
• Others say boosting now is unnecessary, because the shots still prevent hospitalizations and death.
• See more stories on Insider's business page.

The debate over whether the US should roll out extra doses of coronavirus vaccines is reaching a fever pitch.

Pfizer and Moderna, the pharmaceutical companies selling two of the widely used US vaccines, have forcefully argued that booster doses will be necessary before the winter. Some vaccine experts have been just as forceful in saying they aren't needed yet.

"No vaccine, at least not within this category, is going to have an indefinite amount of protection," Dr. Anthony Fauci, the nation's top infectious-disease expert, said in an interview with NBC News on Thursday.

"What we're doing literally on a weekly and monthly basis is following cohorts of patients to determine if, when, and who should get it," he said later. "But right now, at this moment, other than the immunocompromised, we're not going to be giving boosters to people."

Whether it's the opinions of independent experts, recommendations from drug companies, or the latest research fueling the debate, there are compelling arguments for and against rolling out booster doses to the broad US population.

It isn't obvious there's a clear answer at this point, which makes for a good argument as well as a tricky public-health situation. The rise of the Delta variant, which partially lowers protection from vaccines, is adding to the urgency of the situation.

Read more: We got an exclusive look inside Moderna's labs, where the biotech upstart is planning what comes after its blockbuster coronavirus vaccine

The narrow exception here, where both sides agree, is that some Americans do need to be boosted now. Regulators have OK'd third shots for certain people who have severely weakened immune systems, in the hopes of increasing their protection against the coronavirus.

The case in favor: Better safe than sorry

We know that protection from the coronavirus vaccines peaks a few weeks after people get the second dose of a Pfizer or Moderna shot, then gradually declines.

The critical unknown is how fast it wanes and when we should care enough to act.

The vaccine developers Pfizer and Moderna have recently said that third doses should be rolled out between six and 12 months after the first two doses.

In part, that's because data from Pfizer's massive study testing its vaccine shows protection against symptomatic cases of COVID-19 fell from 96% to 84% over six months. Moderna has presented data showing the antibodies produced by its shot are not nearly as abundant and powerful when exposed to circulating variants after about six months.

The companies have also presented lab data showing a third dose significantly increases the level of virus-killing antibodies in people. Those boosted antibodies are also active in fighting the Delta variant. That matters because there's more research suggesting that neutralizing antibodies correlate strongly to protection against COVID-19.

The vaccine makers do have a clear financial incentive to pitch booster doses. Moderna, in particular, has seen its valuation explode from $7 billion to more than $160 billion through the pandemic, thanks to its COVID-19 vaccine work that is now bringing in billions in revenue.

Reports of waning protection are spurring booster shots

Still, information from the UK, Israel, and Mayo Clinic researchers does show that protection from the vaccines seems to be decreasing, adding to the case for boosters.

Perhaps most shockingly, Israeli health officials said they have seen protection against severe illness tumble from 97% in April to 81% in July among people who are 60 and over. While that data has yet to be published or posted on a preprint server, it is informing that country's public-health strategy.

Israel is in the middle of an aggressive booster campaign, opening eligibility for extra doses to everyone 50 years and older and healthcare workers, among others. France and Germany are also forming booster plans that will start to give third shots in September.

So much of the pandemic has boiled down to problems of reacting rather than anticipating and preventing. Signs are emerging that protection is waning, and a booster shot holds the promise of patching up immunity. Why not try to maximize protection with the tools available?

The case against: Boosters are unnecessary, selfish

Dr. Paul Offit, a longtime vaccine developer who sits on the FDA's vaccine advisory committee, says it's not yet time for booster shots.

That's because the objective of these vaccines is not to prevent every infection. Instead, the aim is to prevent people from being hospitalized with COVID-19 or dying. They're still doing that extraordinarily well, Offit said.

When you take that perspective, some of the same studies driving concern look reassuring.

Take the Mayo Clinic study (and it's worth emphasizing that this is preliminary research).

While a sharp drop in effectiveness for Pfizer's vaccine in July has drawn attention, the same study found that its effectiveness at preventing the worst COVID-19 outcomes held up.

The shots are still working

Pfizer's shot was 75% effective at preventing hospitalizations, roughly in line with previous month. Moderna's vaccine was 81% effective by that measure.

Overall, the Mayo results show the vaccines are working, said Maria Elena Bottazzi, a vaccine developer at Baylor College of Medicine.

"It's still not really, really clear by the data if it's advantageous to get a third boost now if you're a normal, healthy person with a normal immune response," Bottazzi said. "We're still seeing great protection by the vaccines against the Delta variant."

Another good example is the outbreak in Provincetown, Massachusetts, which drew headlines because most of the people infected were also fully vaccinated. But a CDC analysis of a subset of those cases found that out of 346 fully vaccinated people who got infected, only four, or roughly 1%, were hospitalized and no one died.

"That's a vaccine that is still working," Offit said.

Much of the world still needs doses

If outbreaks increasingly send fully vaccinated people to the hospital, that's when you'll know we need boosters. That's not happening as of now, Offit said.

Finally, giving boosters overlooks the far more pressing issue of getting more people vaccinated, Offit and Bottazzi said.

The World Health Organization is pleading with rich nations to hold off on boosters until at least the end of September so other countries can get more of their populations immunized.

"I would rather see more people get protected against severe disease and deaths and hospitalizations, even if we all have breakthrough infections because that's what's going to stop this virus from continuing to mutate," Bottazzi said.