At some point, however, herd immunity is achieved: Enough of the population is immune to make the risk of infection minimal in the population as a whole. Anthony Fauci puts the threshold for herd immunity at full vaccination of 85% of the U.S. population, including children. Since the vaccine has been authorized only for patients 16 and older and not all adults are willing to accept it, Dr. Fauci’s goal almost certainly won’t be reached for another year, if ever. The current figure is only 17% of total population.

Dr. Fauci’s benchmark is unreasonably high. He ignores that many unvaccinated Americans—perhaps as many as 120 million, as seroprevalence studies suggest true incidence levels to be three to 20 times captured infections—have immunity owing to prior infection. A recent large-scale Danish study estimates that prior infection confers approximately 80% protection to patients younger than 65 and 47% protection to those older. That difference is why it’s important to prioritize the elderly for vaccination, as U.S. authorities have done. Because of this combination of factors, we will likely surpass 50% combined immunity within the next week or two.