US could reach herd immunity by summer through vaccinations alone, analysis finds

The pace of Covid-19 vaccine administration in the US continues to improve, each day bringing the country closer to herd immunity — the point at which enough people are protected against a disease that it cannot spread.

This week, President Joe Biden said that the US will have enough vaccine for every adult by the end of May, and a CNN analysis of federal data shows that herd immunity is likely not far behind.

At the current pace of about 2 million shots per day — the latest seven-day average of doses administered reported by the US Centers for Disease Control and Prevention — the US could reach herd immunity by summer through vaccinations alone. It will likely be even sooner, if factoring in individuals who may have some natural immunity due to prior infection.

Herd immunity thresholds for Covid-19 are only estimates at this point. But experts generally agree that somewhere between 70% and 85% of the population must be protected to suppress the spread, a range that Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases has recently cited.

More than 8% of the population — nearly 28 million people — is already fully vaccinated, according to the latest data from the CDC.

If vaccination continues at its current rate and the two-dose vaccines from Pfizer/BioNTech and Moderna were the only options available, 70% of the US population could be fully vaccinated by mid-September.

But the US Food and Drug Administration recently authorized the Johnson & Johnson’s one-dose vaccine for emergency use, and the company has promised to deliver 100 million doses to the US in the first half of the year.

At the current pace of about 2 million doses per day, including 100 million doses of the single-shot Johnson & Johnson vaccine, 70% of the US population could be fully vaccinated around the end of July and 85% by mid-September, according to a CNN analysis.

The CDC estimates that more than a quarter of the population may have been infected by Covid-19, bumping the share of the population already protected up to nearly a third. Assuming there’s no overlap between people with natural immunity and those protected through vaccination, herd immunity could be reached as early as June.

Experts note that some new variants threaten progress, potentially lessening protection offered by vaccines and skirting some degree of natural immunity, and vaccine hesitancy may also create some limitations.