From the beginning, I have been projecting that herd immunity would occur much sooner than was being predicted by many of the public health mathematicians. This was because immunity in their calculations was based simply on their estimates of number of people infected with COVID-19, while I felt immunity was more common and provided more effective protective than they believed. Several findings now support my proposition.
-Many individuals have been infected and not diagnosed because they were asymptomatic.
-Individuals appear to have cellular immunity from other coronaviruses including SARS and infections causing “colds.” That provides at least some protection against COVID-19 infection.
-Studies looking for infected patients by screening for antibody have used insensitive tests or tests that only employ a single protein from the SARS-CoV-2 virus that causes COVID-19. This also underestimates infected numbers.
Despite these clear indications that background immunity to COVID-19 was present and could cause herd immunity protection, many people argued this would not be the case. One of the sources of many anti-herd immunity discussions was the New York Times, which ran several Op Ed pieces suggesting it might “never occur” without an effective vaccine.
At long last today’s New York Times published a story entitled What if ‘Herd Immunity’ Is Closer Than Scientists Thought? It indicated that herd immunity may already be present in places like New York City where there were large scale infections and that herd immunity may be much closer than ever suspected in the country as a whole.
Of course, they refer mainly to math models and talk about “new estimates result from complicated statistical modeling of the pandemic” and “inconsistent estimates.” They also talk about having enough immunity to “resist a second wave,” which of course is not relevant since the first wave has never ended.
They also reiterate the criticism of Sunetra Gupta, a theoretical epidemiologist at Oxford University, and one of the few to raise the concept of early herd immunity. She initially said in a widely circulated interview that London and New York may already have reached herd immunity because of variability of immune markers (antibodies) among people, combined with a the potential of immunity to common cold coronaviruses that may protect against the new one. “That could be the explanation for why you don’t see a resurgence in places like New York,” she said.
But the article itself finally raises the possibility that places like NYC are not experiencing further infectious outbreaks because they already have reached a state of herd immunity. In fact, they identify neighborhoods and communities, like Brooklyn’s Hasidic Jews, that are acting like they have herd immunity.
They also point out that you may not have to immunize the entire community to protect individuals at risk, like the elderly. They provide the example of children given the pneumococcal (pneumonia) vaccine in the early 2000s, and then rates of bacterial pneumonia in the elderly rapidly dropped because of a “herd protection effect.”
It is gratifying that this discussion is finally taking place because herd immunity significantly alters the dynamic of the pandemic. It is not simply a hopeful concept, but a realistic development that is more likely to happen than a highly effective vaccine or total social restrictions.
Pandemic Pondering 
Hey, Dr. Baker. Loving your blog — thanks so much!
NY is not experiencing many outbreaks — yes, there are still several every week — perhaps in part because of more widespread immunity, but please don’t discount the behavior of New Yorkers. We are wearing masks for the most part, at least far more than the rest of the country appears to be wearing them, we are still practicing distancing, and we are reopening very, very slowly. The sidewalks are still not crowded, some neighborhoods are empty, the people who left for summer homes or to stay with family have not yet returned, very few people are going into stores, people arriving from other states are required to quarantine for 14 days … We are following strict rules, partly thanks to good state governing and enforcement, but also because we’ve lost 25,000 people in the city, 32,000 total in the state, and we are still scared and still in mourning. Most of us also know people who ‘recovered’ from the virus but, months later, are suffering from serious cardiac, autoimmune, and neurological complications. Yup, we’re being pretty careful.
I think we’ll have to wait until school reopens next month. Should we see no major spikes after three or four weeks of school, then we can consider the possibility of more widespread immunity then the documented numbers indicate. Until then I’m attributing it to a governor who’s handling this well and a population who’s learned the hard way to take precautions seriously.
Regards,
Kathy
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Dear Dr. Baker,
When I hear the number of covid-19 deaths each day, I can’t help but wonder if a number of these deaths are not due to comorbidities rather than to the virus itself. In other words, if people with two or three (or more) comorbidities, catch the virus and succumb; but if they had not had the diabetes, overweight issues, had heart disease, they might have beaten the corona virus? If that is true then the numbers of deaths we hear every day would be inaccurate. What would you say?
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Quite honestly, there are so many problems with reporting of infections and deaths I would only use them as a loose barometer about where the overall trends are heading.
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