The European drugs regulator is holding firm with plans to review Covid-19 vaccines designed to tackle the original coronavirus and the Omicron variant, its head said, in contrast with US authorities who plan to approve these jabs before the release of clinical data on their efficacy.

It might mean Europe receives vaccines tailored to the highly infectious BA.4 and BA.5 Omicron sub-variants later than the US.

It is unclear whether the jabs would be better than shots tailored for BA.1, a previously circulating form of Omicron, because no data is available.

Emer Cooke, head of the European Medicines Agency, said in an interview that reviewing available data was paramount and that her agency would stand firm. The EMA is reviewing two so-called bivalent shots, which incorporate elements from the coronavirus as it appeared in 2019 and BA.1.

“Irrespective of what is happening, we have to have confidence in the vaccines that we authorise, and that is our primary responsibility as we have done with all the vaccines that have been presented to us,” Cooke said.

“All this comparison between BA.1 and BA.4/BA.5 is something I think we’re over-focusing on at the moment,” she added. “Promises are not enough for me.”

Cooke’s remarks contrast with calls made by industry figures who have urged regulators to approve vaccines that incorporate BA.4/BA.5 components without waiting for clinical data.

BioNTech chief executive Uğur Şahin said in June it would be “useful” to adapt vaccines “without the requirement to do extra clinical trials” so that jabs could target the latest strains before the virus mutated further. Moderna has made similar remarks.

The US Food and Drug Administration has recommended manufacturers incorporate BA.4/BA.5 components to the upcoming booster campaign.

Cooke said recent studies indicated that effective rollout campaigns played a more significant role in tackling the virus than the specific effectiveness of each vaccine.

“Frankly, if we started a new wave tomorrow, I’d take the old vaccine, because that’s what is available.”

“Our priority is to ensure that the member states have a plurality of options available that would meet their individual strategies,” she said, noting the state of the epidemic differed greatly within member countries, and that the BA.5 wave had peaked in about half of the EU’s 27 member states.

She said reviews of the BioNTech/Pfizer and Moderna shots would be completed in early September, “if there are no surprises”.

Cooke stressed the agency would be able to move quickly if it became clear that a bivalent shot made to target BA.4/BA.5 turned out to be a better approach. But, she added, this would only be clear when data showing this was the case becomes available.

Health experts have repeatedly said it is possible that a Covid-19 resurgence could put health systems under significant pressure later this year if vaccine protection wanes in the face of new mutation.

Shots currently on the market only target the so-called ancestral strain of coronavirus, as it first emerged in China in late 2019. Those vaccines lose efficacy against transmission of Omicron within months, although they retain good protection against severe disease over time. European health authorities have recommended widening fourth-shot eligibility in the bloc following a recent surge in cases.

The World Health Organization, which has tended to adopt a conservative approach in Covid-19 vaccine policy, has also signalled support for variant-specific vaccines deployed against a virus that is “likely” to continue to evolve.

Asked if she thought the pandemic was over, Cooke said she did not think that was the case. “We need to be prepared for what could be a difficult time in the autumn,” she said.