People are waiting in line for coronavirus disease vaccines (COVID-19) at Martin Luther King Jr. Community Hospital. in Willowbrook, Los Angeles, California, on February 25, 2021.
Lucy Nicholson
The United States is not “very close” to securing herd immunity against Covid, and more transmissible variants mean even more people will have to be vaccinated to get there, a CDC scientist said Friday.
Herd immunity occurs when there are enough people in a given community who have antibodies against a specific disease, either through vaccination or prior exposure to the virus. This makes it difficult to spread from person to person and even protects people who have no immunity.
“We now know that the majority of the U.S. population is not immune to SARS-CoV-2 and that variants can cause an increase in that portion of the population that is not immune,” said Adam MacNeil, an epidemiologist at the Centers for Disease Control and Prevention.
To reach the herd’s immunity threshold as it fights new strains of more contagious viruses, a larger proportion of the population needs to be vaccinated, MacNeil said at a meeting of the Food and Drug Administration reviewing the application Johnson & Johnson to authorize its Covid-19 vaccine for emergency use.
Scientists do not believe that immunity lasts forever. It weakens over time and this could aggravate the outbreak as previously protected people become vulnerable to infection, MacNeil said.
MacNeil’s comments come a week after a Wall Street Journal opinion piece claimed that the United States will achieve herd immunity in April.
Although Covid variants have been shown to decrease the effectiveness of a Covid vaccine in protecting against infection, vaccines have been shown to be effective in preventing serious disease and hospitalizing against the most infectious strains.
The increase in vaccination would substantially slow down the current trajectory of a highly contagious Covid variant that was first identified in the UK to become the dominant virus strain in the US in March, MacNeil said.
MacNeil said the increase in vaccination will be critical for the country to reach the benchmark.
“Vaccination has begun and we hope this will bring us closer to filling the herd’s immunity gap.”