LONDON (AP) — Regulators in the U.K. and four other countries have announced new rules to fast-track the development of modified COVID-19 vaccines to ensure drugmakers can move swiftly to target emerging variants of the disease.

Previously authorized vaccines that are modified to combat new variants “will not need a brand new approval or ‘lengthy’ clinical studies,” Britain’s Medicines and Healthcare Products Regulatory Agency said Thursday.

“The clear goal is that future vaccine modifications that respond to the new variants of coronavirus can be made available in the shortest possible time to U.K. recipients without compromising at any stage on safety, quality or effectiveness,” Dr. June Raine, the head of the agency, said in a briefing for reporters.

The new guidance is based on the model already used to modify the seasonal flu vaccine to keep up with annual changes in the virus and was issued jointly by regulators in the U.K., Australia, Canada, Singapore and Switzerland. The U.S. Food and Drug Administration and European Medicines Agency have issued similar guidance.

Under the new rules, developers will be required to provide “robust evidence” that modified COVID-19 vaccines produce a strong immune response to the variant, as well as data showing they are safe and meet quality standards.

This means developers will be required to carry out small-scale trials on a few hundred people, rather than the trials in tens of thousands of individuals that were required for initial approval, said Dr. Christian Schneider, the MHRA's chief scientific officer.

“I’d like to emphasize that to date we don’t have evidence that the vaccines in use in the U.K. are significantly lacking in effectiveness,” Raine said.

The announcement comes amid concerns that the virus that causes COVID-19 may mutate to create new variants that are resistant to existing vaccines. The U.K. has banned direct flights from 33 countries in an effort to prevent variants first discovered in Brazil and South Africa from becoming established in Britain.

Vaccine makers have already been developing booster shots to target the new variants.

Moderna said Feb. 24 that it had shipped a variant-specific vaccine candidate to the U.S. National Institutes of Health for review.

The coronavirus pandemic has infected over 115 million people around the world and killed at least 2.5 million, according to Johns Hopkins University.

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