Herd Immunity “Not a Possibility” Due to Delta Variant, AstraZeneca Scientist Says

The Delta variant has made it quite impossible to achieve herd immunity, as the variant has changed the equation for vaccines.

In a UK parliamentary meeting held 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 is circulating."

"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," he said.

While it is "unlikely that herd immunity will ever be reached," outbreak of the next coronavirus variant will perhaps be "even better at transmitting in vaccinated populations."

The Delta variant can still infect vaccinated people

Experts previously hoped to achieve herd immunity through vaccines, like that with the highly infectious measles, which ended the endemic transmission in the U.S. in year 2000, but could be a 'perpetual battle' at this time.

With Covid vaccines still fulfilling their primary role which is to protect and develop antibodies to fight against virus, hopes in reaching immunity among herd could be highly unlikely, especially with the Delta variant around.

US Centers for Disease Control and Prevention said that even a vaccinated population could catch the Delta variant with 25 times less likely to have a severe case, posing a mounting threat in the US, and around the world, with mild to no symptoms.

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

Fully vaccinated people could transmit the Delta variant

CDC said that 'the war has changed' with the more infectious Delta variant.

In fact, "the Delta coronavirus variant spreads more easily than the viruses that cause Ebola, the common cold, and smallpox," according to an internal presentation from the Centers for Disease Control and Prevention, and people who are fully vaccinated can spread Delta as easily as those who are unvaccinated.

Nonetheless, updated guidelines recommend using masks again, even for vaccinated people, as the "Delta variant makes it easier for vaccinated people to transmit the virus," CDC said.

"Although it's rare, we believe that at an individual level, vaccinated people may spread the virus, which is why we updated our recommendation," an anonymous federal health official said. "Waiting even days to publish the data could result in needless suffering, and as public-health professionals, we cannot accept that."

Although vaccines remain highly effective in preventing severe illness, hospitalization, or death, Delta infections have generated more severe cases than those of earlier coronavirus variants, increasing demand for oxygen and ICU admissions.

Still, "the vast majority of transmission, the vast majority of severe disease, hospitalization, and death is almost exclusively happening among unvaccinated people," said CDC director Rochelle Walensky.

Assuming that vaccines are 90% to 95% effective, only about 1 in 20, or even 1 in 10 transmission could lead a breakthrough infection.