CDC: Time to Rethink Herd Immunity

The Centers for Disease Control and Prevention may be changing its thinking about how herd immunity fits in with the goal of controlling the coronavirus. At the same time, the waning immunity of vaccinated Americans has taken on more urgency.

November 21, 2021, 9:00 AM PST

By Irvin Dawid


Ron Adar / Shutterstock

“If you really want true herd immunity, where you get a blanket of protection over the country ... you want about 75 to 85 percent of the country to get vaccinated,” said Dr. Anthony Fauci, the nation’s leading infectious disease scientist, in an interview with a Vox on Dec. 15, 2020.

[Related post: "Pandemic Endgame: The Goalposts are Moving," December 30, 2020.]

A day earlier, Sandra Lindsay, a critical care nurse at Long Island Jewish Medical Center in New York, became the first American inoculated with a COVID-19 vaccine. “I believe this is the weapon that will end the war,” said Gov. Andrew Cuomo, reported The Washington Post on the historic day.

Since then, over 195 million Americans, almost 59% of the population, have become fully vaccinated against the novel coronavirus disease that has killed more than 764,000 Americans and well over 5 million people.

Herd immunity out—waning immunity in

Now we learn from Karen Kaplan, a science and medicine editor at the Los Angeles Times who writes their Coronavirus Today newsletter, and Melissa Healy, a D.C.-based health and science reporter also with the Times, that the herd immunity goalposts are moving again. In fact, they appear to have been removed from the field entirely.

Kaplan writes that Healy was covering the Nov. 2 meeting [pdf] of the Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices where they voted unanimously to recommend the COVID-19 vaccine manufactured by Pfizer and its German partner, BioNTech, for use in children aged 5-11 years old.

Dr. Oliver Brooks, a panel member and chief medical officer of Watts Healthcare in Los Angeles, asked CDC representatives to discuss how rolling out the vaccine to children of this age group "could bring the country closer to its herd-immunity goal." [Boldens by Kaplan].

At first, Brooks was met with an awkward silence. Then, Dr. Jefferson Jones, a medical officer on the CDC’s COVID-19 Epidemiology Task Force, spoke up.

“Thinking that we’ll be able to achieve some kind of threshold where there’ll be no more transmission of infections may not be possible,” Jones told the CDC panel. The widespread phenomenon of waning immunity — among people who survived coronavirus infections as well as those who’ve been vaccinated — has made the adoption of a clear herd-immunity goal “very complicated,” he added.

Protection from severe disease vs. transmission

The real value of the three 'first-generation' FDA-approved or authorized COVID-19 vaccines are their ability to prevent serious illness that results in hospitalization. Transmission, on the other hand, is more difficult to stop by vaccinations alone.

"Vaccines have been quite effective at preventing cases of COVID-19 that lead to severe illness and death, but none has proved reliable at blocking transmission of the virus, Jones noted," writes Healy in the source article on Nov. 12. "Recent evidence has also made clear that the immunity provided by vaccines can wane in a matter of months."

The result is that even if vaccination were universal, the coronavirus would probably continue to spread.

“We would discourage” thinking in terms of “a strict goal,” he said.

Impact on vaccinations?

That response did not sit well with Brooks, who noted that "Jones’ unexpected admission 'almost makes you less motivated to get more people vaccinated,'" adds Healy.

However, one of the main reasons that CDC changed its masking guidance on May 13 was to motivate people to get vaccinated, as NPR reported on May 20.

During a situation without historical precedent, the CDC's move is a gamble. The risk of loosening mask guidelines, of course, is that unvaccinated people will no longer feel compelled to wear masks at all.

Two months later, after almost all states had followed the CDC's guidance and ended universal masking, the Delta surge was causing cases to skyrocket in Missouri. While CDC corrected its masking guidance on July 27 after Provincetown, Mass. data showed that vaccinated people could transmit the virus, only six states today require universal indoor masking.

As for any beneficial impact on increasing the vaccination rate, 54 countries have higher percentages of their populations fully vaccinated, according to The New York Times tracker on Nov. 18.

Boosters for all

"With studies showing waning efficacy of initial covid vaccines, the federal government is moving closer to recommending boosters for all adults," states the Kaiser Health News Morning Briefing for Nov. 18. "It is behind several states that now allow them" (e.g., Colorado). The news that the FDA had approved boosters for all adults came just a day later, on November 19, according to an FDA press release.

Additional related posts:

Hat tip to Dr. Monica Gandhi who referenced the source article in a Nov. 15 update to her opinion in the San Francisco Chronicle, "We need to start thinking differently about COVID outbreaks."

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