NEW YORK (Reuters) – A top Pfizer Inc scientist said on Thursday the company is in intensive discussions with regulators to test a booster shot version of its coronavirus vaccine specifically targeted for a highly contagious variant that is spreading widely in South Africa and elsewhere.

Phil Dormitzer, one of Pfizer’s top viral vaccine scientists, said in an interview that he believes the current vaccine – developed with Germany’s BioNTech SE – is highly likely to still protect against the concerning variant first discovered in South Africa.

“We’re not doing that primarily because we think that that means that we’re going to need to change that vaccine,” he said. “It’s primarily to learn how to change strain, both in terms of what we do at the manufacturing level, and especially what the clinical results are.

“So if a variant comes along for which there is clinical evidence of escape, we’re ready to respond very quickly,” Dormitzer added.

Dormitzer, chief scientific officer of viral vaccines at Pfizer Vaccines Research and Development, said the company has already made a DNA template for a prototype vaccine and plans to manufacture a batch of that prototype.

The company is proposing to do a Phase I clinical trial of a booster shot of that prototype vaccine that it would test against a booster for the current vaccine.

“This will be a immunogenicity study where you look at the immune response. And those studies are much, much smaller than the giant efficacy studies,” Dormitzer said.

“In immunogenicity studies you can look at the immune response of every person in the study. So that enables you to have much smaller, easier studies to run. It’s not as definitive as efficacy data, for sure. But it can be gathered much more quickly,” he explained.

The U.S. Food and Drug Administration has not yet released a roadmap for how companies should design trials of booster shots.

A laboratory study released on Wednesday suggested that the South African variant of the coronavirus may reduce the proportion of protective antibodies elicited by the Pfizer/BioNTech vaccine by two-thirds, but it is not clear how much that reduces the shot’s effectiveness against the variant.

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