How boosters will work: Doctors prepare for third vaccine doses for all Americans

TAMPA, Fla. - Federal health officials announced Wednesday third doses of Pfizer and Moderna's COVID-19 vaccines will be available to all vaccinated people eight months after their second dose starting September 20, and Tampa Bay public health experts are weighing on what that means for the public.

Some infectious disease researchers said they wonder what prompted the government to come up with eight months as the threshold for a third dose to boost immunity again.

"None of the data suggest that eight months is any particular number that we should worry about," said Dr. Michael Teng, a USF Health virologist. "There were indications at six months that immunity started waning a little bit."

Dr. Teng said third doses for Pfizer and Moderna are not yet approved for everyone by the FDA and the CDC. The FDA is also still working through the application for Pfizer’s full license that’s expected next month. It’s adding on to a massive task within one month.

"It takes a little bit of time for FDA to review those data, and then they can fairly rapidly amend the emergency use authorization. But then they have to send it over to CDC to say how the immunizations should be done," said Teng.

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Third doses are already approved for immuno-compromised people to bring them to the same level as everyone else. Moffitt Cancer Center in Tampa is ready to help its patients.

"For those immune-compromised people, it's especially important that they get access to that third dose to generate as much of a response as they possibly can. For you or I, if we've got a normal immune system what we know is that this vaccine, like others, frankly, does wane over time, but it's still protective even today," said Dr. Robert Keenan, Moffitt Cancer Center’s chief medical officer.

"There actually have been a reasonable number of people, both in the states and elsewhere, who have gotten a third dose. And as best we can tell, whatever reaction you might have had is not any worse than the reaction after the second dose. So use that as your guide, if you will."

About 13 million people who got the Johnson and Johnson are left out of the booster shot talks for now. That vaccine first went out in March.

"There's no data on Johnson and Johnson's second dose. J & J is actually doing a second dose as part of their clinical trial," said Teng about a current study on the company’s doses. "They had to do a longer duration between doses because they were worried about developing immunity to the vaccine itself rather than SARS-CoV-2."

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Dr. Teng said researchers are getting answers on whether mixing doses can work.

"There are studies going on to look at that for sure.  Moderna enrolled a clinical trial to look at three Moderna doses, two Pfizer doses and a Moderna dose, a dose of J&J and a Moderna dose," said Teng.

National Institutes of health is also testing a mix of vaccine boosters. But whether it’s your third or your first, doctors said you cut your risk of ending up in the hospital.

"It was always a concern was two enough. Well, now we're in a situation we're saying maybe it is enough, but there's enough data out there to say, yeah, a third dose is reasonable and go ahead and do it," said Dr. Keenan. "In Florida, we are seeing hospitalizations of COVID patients at levels we've never seen before. We're seeing large numbers of patients in the ICU and upwards of 85, 90 percent of those individuals are unvaccinated."

With the COVID boosters expected to start during flu season, the CDC recommends spacing out the third COVID dose and the flu shot two weeks apart.

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