US authorises the use of dual-variant covid-19 vaccine boosters

The US Food and Drug Administration authorised the use of versions of Moderna and Pfizer/BioNTech covid-19 vaccines that target both the original virus and two omicron subvariants

The US Food and Drug Administration (FDA) granted emergency use authorisation on 31 August to covid-19 vaccines that target two different coronavirus variants. These updated “bivalent” vaccine boosters from Moderna and Pfizer/BioNTech target both the original strain of the virus and the highly contagious BA.4 and BA.5 omicron subvariants.

People who have had their initial covid-19 vaccine doses or have received their most recent booster at least two months ago will now be eligible for Pfizer/BioNTech’s new booster if they are 12 years or older and Moderna’s updated booster if they are 18 years or older. A press release from Moderna said the company’s boosters should be available in the coming days at vaccination sites across the US; Pfizer/BioNTech announced that they will begin shipping their boosters as directed by the US government

“The updated boosters are expected to provide increased protection against the currently circulating omicron variants,” said Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, during a press conference on 31 August. “Ongoing studies will provide insight into the specific level of robustness of the protection.”

Currently, there is no data on the safety and effectiveness of these boosters in humans. Rather, the FDA made its decision based on data from animal studies, which found that the new vaccines provoked an immune response. The agency also used safety data from previous covid-19 vaccines, including a bivalent one approved for use in the UK, but not in the US, that is designed to target the BA.1 omicron subvariant. This vaccine is very similar to those targeting BA.4 and BA.5, said FDA commissioner Robert Califf in a press conference. The main difference is that the updated boosters contain genetic material for producing antibodies against BA.4 and BA.5 rather than BA.1, he said.

Both Marks and Califf said the approval without data from human trials is similar to how the FDA approves annual flu shots.

“We are pretty confident that what we have is very similar to what we have done in the past with influenza strain change where we don’t have clinical studies,” said Marks.

The FDA chose to authorise the BA.4 and BA.5 bivalent vaccines rather than the BA.1 version because these subvariants account for virtually all new cases in the US. “This gives us a [booster] that is most up to date,” said Marks.

The FDA will no longer authorise the use of the original covid-19 vaccines as a booster for people who are 12 years and older. However, it will still be used as the first and second dose for people who haven’t had both these jabs and will be available as a booster for those under the age of 12.

“The more updated you are on the vaccine, the greater the chance you will be protected,” said Califf. “We have to be a step ahead or at least try to be a step ahead [of covid-19].”

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