Prof Sir Andrew Pollard, Head of the Oxford Vaccine Group said MPs in the all-party parliamentary group on coronavirus that reaching herd immunity is not a possibility with the current Delta variant.
He shared evidence that the vaccines did not stop the spread of Covid-19, which made the threshold for herd immunity "mythical".
Pollard noted that the Delta variant is infecting people who have been vaccinated. And vaccinated people will be interacting with unvaccinated people at some point in their day. There is nothing that will completely stop that transmission.
He drew an analogy from measles and clarified that if 95% of the population were vaccinated against measles, only 5% is vulnerable to the virus. In the case of coronavirus, that is not the case, he explained.
Vaccines that have been designed so far have only been successful in preventing serious illness and death in Covid-19 patients. However, a fully vaccinated individual is not yet in the clear. A study at the Imperial College London says that fully vaccinated people of the age group 18-64 are at 49% lower risk of getting infected.
Meanwhile, about 75% of the UK's population have got vaccinated to date. The health secretary, Sajid Javid said that the government is planning to offer Covid booster shots to the most vulnerable groups. However, Pollar opined that booster shots are needed only if there is an increase in hospitalisation cases.
The Joint Committee on Vaccination and Immunisation (JCVI) recommended that vulnerable children in the age group of 12-15 be vaccinated. Those who live with high-risk adults are also eligible for vaccination in many countries. US, Ireland, and Israel have decided to vaccinate children under the age of 16 to contain the virus.