LONDON — Achieving herd immunity with Covid-19 vaccines when the highly-infectious delta variant is spreading is “not a possibility,” a leading epidemiologist has said, with experts agreeing that such a goal — where overall immunity in a population is reached and the spread of the virus is stopped — is not likely for several reasons.
Professor Andrew Pollard, the head of the Oxford Vaccine Group, told British lawmakers Tuesday that as Covid vaccines did not stop the spread of the virus entirely — with vaccinated people still able to be infected and transmit the virus — the idea of achieving herd immunity was “mythical.”
“I think we are in a situation here with this current variant (the delta variant) where herd immunity is not a possibility because it still infects vaccinated individuals,” Pollard, one of the lead researchers in the creation of the AstraZeneca-University of Oxford vaccine, said.
“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.”
Read more: Fully vaccinated people are still getting infected with Covid. Experts explain why
What is herd immunity?
Put simply, herd immunity relates to the idea that a high level of immunity to a virus in a population can be achieved by both natural infection (through the forming of antibodies when the body fights a virus) and by vaccination.
The latter method is preferred as vaccines overwhelmingly create immunity without causing illness or adverse health complications, unlike the natural infection route.
The antibodies procured by both natural infection and vaccination usually protect against future infection and if enough people in a population are immune this leads to lower rates of prevalence of disease or viruses in a community. If a virus has less opportunity to spread and infect, it can be greatly controlled or even eradicated.
With herd immunity, those who are not vaccinated (whether through choice or because they cannot be immunized at a given point — newborn babies, for example) are protected by the overall level of immunity present in a population.
Mass, successful vaccination programs have meant deadly, contagious viruses and diseases such as polio, tuberculosis and measles have been largely eradicated in parts of the world or greatly suppressed by vaccination programs and the herd immunity they foster.
