Delta Variant Makes Herd Immunity Impossible – AstraZeneca Scientist

According to the developer of the Oxford/AstraZeneca vaccine, the Delta variant has changed the equation for achieving herd immunity. He said this while speaking at a UK parliamentary meeting on Tuesday.

Sir Andrew Pollard, a professor of pediatric infection and immunity at the University of Oxford, said that achieving herd immunity is "not a possibility" now that the Delta variant has taken over.

"We know very clearly with coronavirus that this current variant, the Delta variant, will still infect people who have been vaccinated, and that does mean that anyone who’s still unvaccinated, at some point, will meet the virus," Pollard said.

Andrew Pollard

Andrew Pollard
BSc MBBS PhD (Lond), DIC, MRCP (UK), FHEA, FIDSA, FRCPCH, MA, FMedSci
PROFESSOR OF PAEDIATRIC INFECTION AND IMMUNITY
Current research activities include clinical trials of new and improved vaccines for children and adults, surveillance of invasive bacterial diseases and pneumococcal vaccine impact in children in Nepal, studies of cellular and humoral immune responses to glycoconjugate and typhoid vaccines, and development of a serogroup B meningococcal vaccine.

He also said it was very unlikely that herd immunity will ever be reached because the next Covid-19 variant will be "perhaps even better at transmitting in vaccinated populations". Vaccinated people can still be infected with the Delta variant, but as a milder case.

This might dampen the hopes for some experts had hoped that herd immunity could be reached with COVID-19, just like with the case of measles, which is also highly infectious. Many countries have achieved herd immunity with measles by vaccinating 95 percent of the population against it. That is because once a person is vaccinated against measles, they cannot transmit the virus. However, with COVID-19, vaccines still protect against severe disease but a vaccinated person can still transmit the virus.

According to the US Centers for Disease Control and Prevention, vaccinated people who catch the Delta variant are 25 times less likely to have a severe case or die. The overwhelming majority of vaccinated people who do catch Covid-19 will have mild to no symptoms at all. However, with the Delta variant, fully vaccinated people can still transmit the virus.

"We don’t have anything which will stop that transmission to other people," Pollard said.

A good example of what Pollard is saying happened in Israel. COVID-19 cases dropped in the country after it vaccinated about 80 percent of adults – prompting hopes that it had reached herd immunity. However, the Delta variant has since brought another surge of cases.


Sydney Chako

Mathematics, Chemistry and Physics teacher at Sytech Learning Academy. From Junior Secondary School to Tertiary Level Engineering Mathematics and Engineering Science.

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