Achieving herd immunity with Covid vaccines when the highly infectious delta variant is spreading is “not a possibility,” a leading epidemiologist said.
Sir Andrew Pollard, head of the Oxford Vaccine Group, told British lawmakers Tuesday that “I think we are in a situation here with this current variant where herd immunity is not a possibility because it still infects vaccinated individuals,” said Pollard, one of the lead researchers in the creation of the AstraZeneca-University of Oxford vaccine.
“And that does mean that anyone who’s still unvaccinated, at some point, will meet the virus. That might not be this month or next month, it might be next year, but at some point, they will meet the virus and we don’t have anything that will stop that transmission.”
Pollard noted on Tuesday that Covid, and the current virulent delta variant, are different. “The problem with this virus is [it is] not measles. If 95% of people were vaccinated against measles, the virus cannot transmit in the population,” he told the U.K.’s All-Party Parliamentary Group on the coronavirus.
“I suspect that what the virus will throw up next is a variant which is perhaps even better at transmitting among vaccinated populations and so that’s even more of a reason not to be making a vaccine program around herd immunity.”
“The delta variant is highly transmissible meaning that the proportion of people needing to be fully vaccinated for herd immunity is probably not achievable,” he said. “The vaccines provide very effective protection against severe disease/hospitalisation/death but are less effective in preventing infection, mild disease and transmission, especially for the delta variant.”
“However, even without complete ‘herd immunity,’ the higher the proportion of the population fully immunized, the lower the incidence of infection in the community,” he said.
Danny Altmann, professor of immunology at Imperial College London, told CNBC that he also agreed with Pollard. “The whole herd immunity thing was one of those bits of medical textbook-speak that was adopted early on by policy advisors, then the press, then the public and has throughout been contorted and over-simplified,” he said Thursday.
What was important, Altmann said, was that “the more people on the globe effectively vaccinated, the fewer viral copies we’ll have on the planet, thus the less spread and fewer lungs in which for the virus to mutate and spread the next wave of variants.”