This time last year, the brand new, stunningly effective Covid-19 vaccines were rolling out across the country, injecting a strong note of optimism into the United States’ once fumbling pandemic response.
Millions of people were lining up daily to get their shots. Instead of the steady drumbeat of cases, hospitalizations and deaths, we were tracking a new number: the percentage of Americans who had been vaccinated. This number, we believed, was our best chance to beat the virus.
The US was caught up in a fever dream of reaching herd immunity, a threshold we might cross where vulnerable individuals — including those too young to be vaccinated or those who didn’t respond well to the vaccines — might be protected anyway because, as a community, we would weave an invisible safety net around them.
With herd immunity, if someone does get infected by a virus, they are surrounded by enough people who are shielded against infection that the virus has nowhere to go. It fails to spread.
As a country, we had reached this point against some formidable viruses, such as rubella and measles. We thought we could get there with Covid-19. We were probably wrong.
“The concept of classical herd immunity may not apply to Covid-19,” Dr. Anthony Fauci, director of the National Institutes of Allergy and Infectious Diseases, said in an interview with CNN.
How we beat measles
Fauci points to measles as an ideal case study in herd immunity.
Like the virus that causes Covid-19, the measles virus spreads through the air. It is so contagious that if one person has it, 9 out of 10 people around them will catch it if they are not immune to it, according to the CDC. Some experts have estimated that the Omicron viruses are as contagious as the measles.
The US eliminated transmission of measles and has successfully kept the virus from circulating in this country because of three things: an extremely effective vaccine; a virus that doesn’t change, or mutate, in significant ways over time; and a successful childhood vaccination campaign.
The rest is here: https://www.cnn.com/2022/04/15/health/covid-19-herd-immunity/index.html