The New York Times published an article on May 3 with the headline: “Reaching ‘Herd Immunity’ Is Unlikely in the U.S., Experts Now Believe.” “Herd immunity” spiked in search interest on Google, with many searching for the percentage to achieve herd immunity.
The latest articles have social media users talking about how many people actually need to be vaccinated to achieve herd immunity, claims that herd immunity is impossible to obtain, and that vaccinations for children could help the U.S. reach herd immunity.
THE CLAIM: Herd immunity can only be reached if the entire U.S. population is vaccinated
No. Herd immunity protects portions of the population that are unable to be vaccinated, so it means a majority of the population is vaccinated but not 100% of the population.
WHAT WE FOUND
The World Health Organization explains in its definition of herd immunity that “a substantial proportion of a population would need to be vaccinated” to achieve herd immunity. It further explains one of purposes of herd immunity “is to keep vulnerable groups who cannot get vaccinated (e.g. due to health conditions like allergic reactions to the vaccine) safe and protected from the disease.”
“Even individuals not vaccinated (such as newborns and the immunocompromised) are offered some protection because the disease has little opportunity to spread within the community,” the Association for Professionals in Infection Control and Epidemiology includes in its definition of herd immunity.
The reason this works, according to the Department of Health and Human Services, is because “when enough people are vaccinated against a certain disease, the germs can’t travel as easily from person to person — and the entire community is less likely to get the disease.”
Many experts believe that the herd immunity threshold for COVID-19 will be 70% at minimum, but could be higher. The Centers for Disease Control and Prevention says 44.4% of the total U.S. population has received at least one dose and 31.8% of the total U.S. population is fully vaccinated as of the afternoon of May 3.
THE CLAIM: Herd immunity can be achieved without vaccinating children
It’s extremely unlikely. Children are included as part of the total population when calculating herd immunity and nearly every adult in the United States would have to get vaccinated to reach the thresholds in current estimates.
WHAT WE FOUND
The United States Census Bureau estimated in 2019 children younger than 18 made up about 22.3% of the total population. While that includes 17 year olds and 16 year olds who are eligible for the vaccine, that still tells us roughly 80% of the population is eligible for the vaccine.
Polls from the nonprofit Kaiser Family Foundation have found 13% of adults who responded would definitely not get the vaccine and another 7% would only get vaccinated if they were required to. That’s about 20% of the adult population who are unlikely to get vaccinated. If 20% of adults don’t get vaccinated and children don’t get vaccinated either, that leaves about 64% of the population vaccinated. While the threshold needed to reach herd immunity is still unknown, experts have estimated that between 70% and 90% of Americans will need to be vaccinated to reach community immunity.
As of the afternoon of May 3, the Centers for Disease Control and Prevention says 44.4% of the total U.S. population has received at least one dose and 31.8% of the total U.S. population is fully vaccinated.
Clinical trials are currently underway for vaccines for children, first for children 12 and over and now also for children under 12, according to a Yale article about the school’s participation in the trials. The article explains that clinical trials for children take longer than those for adults because of additional safety considerations regarding the development of children’s bodies.
According to news reports, the FDA is expected to approve Pfizer’s vaccine for children 12 and over soon.
THE CLAIM: We know how many people need to get vaccinated to achieve herd immunity
No. Public health experts have estimates, but acknowledge that the actual threshold is still unknown and subject to change based on factors including variants, location and behavior.
WHAT WE FOUND
The Centers for Disease Control and Prevention says as of April 28 it is “still learning how many people have to be vaccinated against COVID-19 before most people can be considered protected.” The World Health Organization’s December 31 update said, “the proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors.”
Writers from the Johns Hopkins Bloomberg School of Public Health elaborated in early April that when communities reduce their level of interaction, infection rates go down and thus the threshold needed to achieve herd immunity also goes down. Infection rates can go up if a society opens more broadly or the virus mutates to become more contagious, which would mean a larger portion of the population would need to be vaccinated in order to reach herd immunity. Additionally, the virus can spread and mutate in other countries with less vaccinated populations, and those mutations could potentially resist older vaccines, adding a level of unpredictability in calculating herd immunity.
Those writers said at least 70% of the population would need to be vaccinated to reach herd immunity based on what is known so far. An article from University of Missouri Health estimates a higher threshold for herd immunity: 80-90%.
This story is part of our VERIFY Weekly series. Check out other VERIFY Weeklies on our YouTube channel.