US FDA authorises two Covid boosters targeted at Omicron subvariants

US approves Omicron vaccines from Moderna and BioNTech/Pfizer

The US Food and Drug Administration on Wednesday authorised updated COVID-19 booster shots from Pfizer /BioNTech and Moderna that target the dominant BA.4 and BA.5 Omicron subvariants, as the government prepares for a fall vaccination campaign that could begin in a few days.

Both vaccines also include the original version of the virus targeted by all the previous COVID shots.

The FDA authorized the shots for everyone over aged 12 who has had a primary vaccination series and is at least two months out from a previous booster shot, shorter than prior recommended intervals. That marks a shift from the current shots based only on the original virus that are available to people 50 and older or who are immunocompromised.

Moderna's retooled vaccine was authorized for those aged 18 and above while the Pfizer/BioNTech shot will be available for those aged 12 and above, the FDA said.

“As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a (duel targeted) COVID-19 vaccine to provide better protection against currently circulating variants,” FDA Commissioner Robert Califf said in a statement.

Experts have said that the updated vaccines will be important for older people and those who are immunocompromised but said there is limited data to support the level of protection the government has promised.

"The idea is they want protection against infection to be generated as quickly as possible in the population, but it's unclear yet how clinically efficacious these vaccines are against BA.5 infection, and if a shorter wait period will impact efficacy because of interference by the prior immunity," said Dr. Amesh Adalja, infectious disease expert at the Johns Hopkins Center for Health Security in Baltimore.

The government has already started working on the fall rollout, which could begin in the next few days after the U.S.

Centers for Disease Control and Prevention's (CDC) outside expert panel meets on Thursday and agency Director Rochelle Walensky makes a final recommendation.

Pfizer said it has some doses ready to ship immediately and can deliver up to 15 million doses by Sept 9.

The U.S. government has secured 105 million doses of Pfizer's updated shots and 66 million doses of Moderna's to stave off the worst effects of a likely surge in infections as schools reconvene and people spend more time indoors as the weather grows colder.

Other countries including Canada and the UK also have ordered updated Omicron vaccine boosters for fall campaigns, although they have purchased shots tailored to the BA.1 Omicron subvariant that caused the record surge in COVID cases last winter.

The FDA in June diverged from other countries when it asked vaccine makers to tailor shots to the BA.4/BA.5 subvariants of the virus that are responsible for the most recent surge in infections worldwide. The BA.5 subvariant accounts for more than 88% of U.S. infections.

The vaccine makers have not completed testing of the updated BA.4/BA.5-based boosters in humans. The FDA is basing its decision on safety and effectiveness data from the original shots as well as from clinical trials conducted on boosters using the BA.1 Omicron subvariant.

"We are confident in the evidence supporting these authorizations," said Dr. Peter Marks, a senior official overseeing vaccines at the U.S. FDA.

Dr. Gregory Poland, a vaccine expert at the Mayo Clinic, said the new shots are unlikely to help those who have been recently infected.

"Its greatest advantage will be in those who are not vaccinated or not fully vaccinated, or those who are immunocompromised," he said.