‘Mix & match’ Covid boosters may gird immunity: EMA

The use of so-called “mix and match” Covid-19 vaccine boosters may give a stronger immune response than sticking to one type of jab, the EU’s drug watchdog said on Thursday.

The European Medicines Agency (EMA) said it was studying data to see if it will follow a decision by US authorities on Wednesday to allow the use of a different vaccine for follow-up shots.

The Pfizer-BioNTech, Moderna, Johnson & Johnson and AstraZeneca vaccines are authorised in the EU. So far only Pfizer is cleared for boosters in adults.

“We are seeing some promising results from studies that confirm that this approach would trigger, with certain vaccine combinations, a stronger immune response than when the same vaccine is used for an additional shot,” Marco Cavaleri, the EMA’s head of vaccine strategy, told a news conference.

Several countries have already approved Covid booster shots to increase immunity in people who have already been vaccinated but whose protection may have dipped after several months, although usually using the same type of vaccine.

A study released in the United States last week showed that people who have received the J&J vaccine — which like AstraZeneca uses viral vector technology — may benefit from a booster dose of a different, messenger-RNA vaccine such as Pfizer or Moderna.

Messenger RNA vaccines “seem to be working quite well” as boosters and “are really able to mount quite a robust immune response”, Cavaleri said.

But Cavaleri added that “overall it seems that the strategy is something that all types of vaccines could be benefitting from,” he added.

The Amsterdam-based EMA is also due to decide on October 25 whether to approve Moderna boosters, Cavaleri said.

Pfizer said earlier Thursday that a booster shot of its vaccine is 95.6 percent effective against symptomatic infection.

The EMA meanwhile said it expects to decide within “approximately two months” whether to extend approval of the Pfizer jab to children aged 5-11, after its makers submitted data last week.

The regulator also expects to start a review next week of an oral Covid drug produced by the US pharmaceutical firm Merck, Cavaleri said.

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