Herd immunity ‘not a possibility’ with Delta variant

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Head of Oxford Vaccine Group says vaccination won’t stop spread altogether.


LONDON — Herd immunity is “not a possibility” with the current spread of the Delta variant due to it still infecting vaccinated individuals, the head of the Oxford Vaccine Group Andrew Pollard said Tuesday.

Pollard, who was involved in the development of the Oxford/AstraZeneca COVID-19 vaccine, told the U.K.’s All-Party Parliamentary Group on coronavirus that, unlike measles — where 95 percent vaccination of the population would stop transmission — the same couldn’t be said for coronavirus spread by the Delta variants.

“That does mean anyone still unvaccinated at some point will meet the virus,” he warned. Pollard said that vaccines may slow the process of transmission, with data indicating that people who are vaccinated and test positive seem to be shedding the virus for a slightly shorter period of time. However, given the circulation of the highly transmissible Delta variant vaccination wouldn’t stop spread altogether.

“We are in a situation with this current variant where herd immunity is not a possibility because it still infects vaccinated individuals,” he said. “I suspect that what the virus will throw up next is a variant which is perhaps even better at transmitting in vaccinated populations. So that’s an even more of a reason not to be making a vaccine program around herd immunity.”

Pollard explained that one of the strongest arguments for vaccinating children is to protect adults. However, he said that vaccinating children wouldn’t completely stop transmission and that there was an urgent need to ensure adults are vaccinated the world over. Countries around Europe are currently discussing whether to offer a vaccine to all teenagers — with varying decisions being made.

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