CDC scientists say the US is “nowhere shut” to herd immunity

People await vaccinations against coronavirus disease (COVID-19) at Martin Luther King Jr. Community Hospital in Willowbrook, Los Angeles, California on February 25, 2021.

Lucy Nicholson

The US is “far from” achieving herd immunity to Covid, and more communicable variants mean even more people will need to be vaccinated to reach them, a CDC scientist said Friday.

Herd immunity occurs when enough people in a particular community have antibodies to a particular disease, either through vaccination or through previous exposure to the virus. That makes it difficult to spread from person to person and protects even people who don’t have immunity.

“Currently we know that the majority of the US population is not immune to SARS-CoV-2 and variants can cause that portion of the population that is not immune to gain weight,” said Adam MacNeil, epidemiologist at Centers for Disease Control and Contraception.

Reaching the herd immunity threshold in combating new, contagious strains of the virus requires vaccinating a higher proportion of the population, MacNeil said at a meeting of the Food and Drug Administration at which Johnson & Johnson’s application for approval of the Covid-19- Emergency vaccine checked for use.

Scientists don’t believe that immunity lasts forever. It weakens over time, and that could make the outbreak worse as previously protected people become vulnerable to infection, MacNeil said.

His comments come a week after a Wall Street Journal statement claimed the U.S. would achieve herd immunity by April.

While virus variants have been shown to reduce the effectiveness of a Covid vaccine at protecting against infection, vaccines have been shown to be effective at preventing serious illness and hospitalization against the more infectious strains.

Increased vaccination would significantly slow current development of a highly contagious variant of Covid, first identified in the UK, as it became the dominant strain of virus in the US by March, MacNeil said.

He said increased vaccination was critical for the country to hit the benchmark.

“Vaccination has started and hopefully this brings us closer to closing the herd immunity gap.”