NIH testing effectiveness, safety of mixing COVID-19 vaccines with potential boosters

BETHESDA, Md. - The National Institute of Health has begun clinical trials for patients who have received both doses of the COVID-19 vaccine to give them a different third booster shot to test the effectiveness and safety of mixing vaccines, the NIH announced on Monday. 

For example, if a patient received both doses of the Moderna vaccine, the NIH is attempting to determine whether or not receiving a third booster shot of Pfizer will be just as effective and safe as receiving a booster shot from Moderna. 

The trial is being funded by the NIH in correspondence with the Infectious Diseases Clinical Research Consortium, a network of clinical trials which cover the institute’s effort to test vaccines and treatments for deadly diseases like the novel coronavirus.

The trial comes as many medical experts are attempting to determine whether or not booster shots will be necessary if the current vaccine’s effectiveness begins to wane months after being administered. 

The CEO of pharmaceutical giant Pfizer said in April that people will "likely" need a third dose of the COVID-19 vaccine.

CEO Albert Bourla told CNBC that the shot would need to be administered within 12 months of getting fully vaccinated and then, possibly, every year after.

"It is extremely important to suppress the pool of people that can be susceptible to the virus," said Bourla to CNBC. 

Earlier this month, Pfizer announced that clinical trials have found its vaccine continued to be effective against COVID-19 up to six months later.

A recent study from Pfizer finds the company’s COVID-19 vaccine maintains more than 90% efficacy at six months after receiving the second dose. Moderna released similar findings on the efficacy of its own vaccine in March.

RELATED: Fauci says variants are ‘wild card’ in COVID-19 booster vaccine equation 

In an interview with FOX Television Stations April 6, Dr. Anthony Fauci, the nation’s top infectious disease expert, said it is entirely conceivable that vaccinated people may need to get booster vaccines down the road, but he doesn’t yet know what the intervals will be between getting a vaccine and a potential booster shot — if booster shots ever come. 

The current dearth of data on vaccine efficacy after the six-month mark illustrates how much remains unknown more than a year into the ever-changing pandemic.

The first person in the United States to receive a COVID-19 vaccination got their shot in December. That first vaccination gave way to an all-out effort to get shots into the arms of beleaguered front-line health care workers, who faced wave after wave of critically ill coronavirus patients filling the halls of ICUs across the U.S.

For those health care workers who were among the earliest vaccinated, the existing data on the length of vaccine efficacy paints an incomplete picture of how long they can expect to be fully protected against the virus. Fauci said it’s just too soon to tell.

RELATED: Immunity to COVID-19 could last for years, new studies suggest

"We don’t know the answer to that for the simple reason that we don't know what the durability of the protection against the standard virus is," Fauci said. "The most recent reports said at least six months but it might be much longer than it could be years for all we know."

"Although the vaccines currently authorized by the U.S. Food and Drug Administration offer strong protection against COVID-19, we need to prepare for the possibility of needing booster shots to counter waning immunity and to keep pace with an evolving virus," said Fauci, on Tuesday, regarding the most recent NIH trial. "The results of this trial are intended to inform public health policy decisions on the potential use of mixed vaccine schedules should booster doses be indicated."

As to what a potential COVID-19 vaccine booster could look like, Fauci previously said additional doses could be drawn from current vaccine stockpiles, but the NIH is currently testing a boost that would specifically target mutations of the virus. 

If vaccine booster shots do become necessary, Fauci said it would be optimal for people to get the same vaccine they received the first time, but there are currently studies underway to see if individuals can mix and match vaccines down the road.

For now, Fauci said the goal should be getting as many people vaccinated as possible — not just in the U.S., but around the world.

"If we suppress it in the United States or in the developed world, that’s going to be great," Fauci said. "Now, this brings up an important question: As long as you have virus replicating anywhere in the world, the chances of developing variants are considerable, which will ultimately come back and could perhaps negatively impact our own response. That’s one of the real prevailing arguments for why we need to make sure the whole world gets vaccinated – not just the people in the developed world."

This story was reported from Los Angeles.