Experts say herd immunity is even harder to achieve with Delta Variant

BIRMINGHAM, Ala. (WBRC) - With Alabama’s low vaccination rates and the spread of the more contagious Delta variant, top doctors are predicting it will be even harder to reach herd immunity.

UAB infectious disease expert Dr. Michael Saag said the number of people who need to have immunity to reach herd immunity is dependent on the infectiousness of the virus.

Saag said the original Covid virus from 2020 reproduced or infected at a rate of two R naught. He said the Delta variant is reproducing and infecting at a rate of four or five R naught.

He said that means Delta spreads easier and faster, which means more people need to have immunity before we would reach herd immunity.

“That means the proportion of people that have to have immunity probably just went up by 20%,” Saag said. “It went from say 75% to 90 or 95 % who would have to have immunity in a herd immunity scenario.”

Dr. Saag said it’s important not to focus on herd immunity too much. He said it is more important to focus on getting everyone vaccinated. He said until that happens, we will likely still see Covid outbreaks over time.