A new study from the Center for Disease Control and Prevention, which shows that a single dose of either the Pfizer-BioNTech or the Moderna vaccine protects against infection by the SARS-CoV-2 virus that causes COVID-19, raises the strong likelihood that we are close to achieving herd immunity for the pandemic. Herd immunity occurs when enough people become immune to a disease—either through being infected and recovering or being vaccinated—to make its further spread unlikely. It is believed that roughly 70 to 75 percent of the population needs to be immune to reach herd immunity for COVID-19.
The study found that the two vaccines, which account for nearly all the vaccines administered in the U.S. so far, reduced the risk of infection with SARS-CoV-2 by 80 percent following a single vaccine dose and by 90 percent for the full two dose regimen. That is far better than the effectiveness of the annual influenza vaccine where the effectiveness in preventing infection ranges from year to year between 10 and 60 percent. The U.S. has fully vaccinated 16 percent of the population against COVID-19 and provided at least one dose to 29 percent. That means nearly a third of the population already has good vaccine protection.
It is significant that vaccinations have been concentrated in the population at highest risk. COVID-19 presents minimal risk to the under-18 age group. Only 238 people under 18 have died—0.05 percent of total COVID-19 deaths. Twenty-one percent of the population 18 and older has been fully vaccinated and 38 percent have received at least one dose. In the most vulnerable population, 65 and older, which accounts for 81 percent of COVID-19 deaths, more than half are fully vaccinated and 74 percent have received at least one dose.
Adding in the people who have natural immunity because of recovery from COVID-19 gets us close to the herd immunity threshold. There have been over 30 million confirmed COVID-19 cases in the U.S. Since the true number of infections may be eight times as high, there may be over 200 million recovered people—about two thirds of the total population—with natural immunity.
Given the number of people vaccinated, the ongoing pace of vaccinations, at over 2 million administered per day, the now ample supply of vaccine doses, and the number of people with natural immunity, we are likely close to reaching herd immunity. We should start to see new cases, hospitalizations, and deaths level off and begin to decline. This will permit the lifting of restrictions and the resumption of normal activities and business.