FDA greenlights mix-and-match booster doses

The Food and Drug Administration (FDA) amended its emergency use authorization for all COVID-19 vaccines on Wednesday to allow for mix-and-match boosters for patients who initially received a different vaccine.

The federal agency also authorized booster shots for Americans who received the Moderna and Johnson & Johnson inoculations. The FDA had previously authorized boosters for the Pfizer vaccine. 

The decision will allow recipients of all three vaccines to get booster doses from other companies, if and when the Centers for Disease Control and Prevention (CDC) issues an official recommendation, which could come as early as Thursday.

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"The available data suggest waning immunity in some populations who are fully vaccinated. The availability of these authorized boosters is important for continued protection against COVID-19 disease," acting FDA Commissioner Janet Woodcock said in a statement. 

“As the pandemic continues to impact the country, science has shown that vaccination continues to be the safest and most effective way to prevent COVID-19, including the most serious consequences of the disease, such as hospitalization and death,” she added.

The FDA’s move supporting mixed vaccine doses follows a preprint study from the National Institutes of Health that found that mixing and matching any of the three vaccines authorized in the U.S. was safe and effective. 

Allowing mixed boosters is likely to smooth the messaging and logistics of the booster rollout by allowing pharmacists and doctors the flexibility to administer available shots to patients.

Peter Marks, director of the FDA’s vaccines division, in a statement said the agency included the use of mix-and-match boosters to address a “public health need.” 

Moderna was granted authorization for a half dose of its vaccine as a booster, for people older than 65, adults with underlying conditions and those with jobs or living situations that put them at risk of contracting the virus at least six months after the initial series. 

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Johnson & Johnson’s extra dose would be available at least two months after vaccination for everyone 18 years and older.

The broader eligibility is a reflection that the vaccine offers a lower level of protection than the shots from Moderna and Pfizer.

During a media briefing late Wednesday, Marks and Woodcock acknowledged that the different eligibility criteria for boosters can be confusing for the general public, but the agency is developing charts other material to help providers better understand.

"We have tried to keep this as uniform as possible but it was not possible to have it totally uniform, because we're dealing with different vaccines," Woodcock said.

"Although it is not simple ... it's not utterly, hopelessly complex, and so hopefully with some clear illustrations, it will be somewhat more accessible what's going on here," Marks added.

The majority of fully vaccinated people, at almost 105 million, received the Pfizer-BioNTech doses, according to CDC data. 

Almost 70 million Americans are fully vaccinated with the Moderna series, while slightly more than 15 million received a Johnson & Johnson shot. That number reflects a later arrival on the market and a troubled rollout that included manufacturing problems and a ten day pause to investigate rare but serious blood clots. 

CDC Director Rochelle WalenskyRochelle WalenskyEurope's COVID-19 surge highlights warnings for US Tensions emerge over redefining the fully vaccinated Israel begins vaccinating kids aged 5 to 11 MORE signed off on booster doses of the Pfizer-BioNTech vaccine late last month, which gave nearly 60 million Americans eligibility.

The CDC’s Advisory Committee on Immunization Practices is likely to provide more detailed guidance during its meeting Thursday, and experts hope the agency emphasizes that people who need a booster should try to receive the same vaccine as their primary dose.

Woodcock said during the briefing she anticipates people will not seek out different doses.

"We would expect many people will continue to get the same series that they had already received," Woodcock said. 

The FDA is also reportedly considering lowering the age of eligibility for booster shots to people aged 40 and older, without any underlying health conditions.

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During the briefing, Marks indicated such a move was likely to happen but did not give a timeframe.

"There is evidence to suggest potentially that lowering the age of those eligible for boosters may make sense in the future, something we're looking at closely," Marks said.  

"The nice thing about our [emergency use authorization] authority is that we are relatively nimble. It is something that can happen as soon as we see and feel that we need to take that action, and the exact age that we take will be based on what we see in terms of the emerging situation."

Updated at 7:34 p.m.