Underestimating Natural Immunity


The rates of Covid-19 infection are falling fast and vaccines are getting much of the deserved credit. But what about natural immunity? The once-revered and now embattled Dr. Anthony Fauci told us months ago that we had to have vaccination rates of 70 to 85% before we would ever reach “herd immunity.” But there was never any mention of the importance of natural immunity.

Dr. Marty Makary, professor of medicine at Johns Hopkins School of Medicine, has been an outspoken critic of this lack of accounting for the impact of natural immunity. I wrote of this three months ago in a post called Herd Immunity is Near. Now he brings us up to date on our progress in a recent Op-ed in The Wall Street Journal.

Dr. Makary says today some 80 to 85% of Americans are immune to the virus. More than 64% have received at least one vaccine shot and, of those who haven’t, roughly half have natural immunity due to prior infection. What’s more, this natural immunity is effective and durable, and public health officials should pay it heed.

Although only about 10% of Americans have had confirmed positive Covid tests, four to six times as many have likely had the infection. This data comes from a February study in Nature which used antibody screenings in late summer 2020 to estimate there had been seven times as many actual cases as confirmed cases. A similar study, by the University of Albany and New York State Department of Health, revealed that by the end of March 2020 – the first month of New York’s pandemic – 23% of the city’s population had antibodies. This number certainly grew exponentially as the pandemic spread.

This means that with more than 8 of 10 adults protected from either contracting or transmitting the virus, it can’t readily propagate by jumping around in the population. Dr. Makary says this is the definition of “herd immunity” – broadly defined on the Johns Hopkins Covid information webpage as “when most of a population is immune.”

The proof of this is the declining rates of infection and hospitalization all across the nation. In Los Angeles, 45% of city residents were found to have antibodies in February. Once vaccines were introduced, the seven-day average of daily Covid cases fell from a peak of more than 15,000 on January 11 to 253 four months later, even as people became more mobile. This dramatic drop in rates can’t be accounted for by vaccination rates alone, which were less than 50% at the time.

Some are concerned that virus variants could change all this. But none of the hundreds of variants observed so far have evaded either natural or vaccinated immunity with the three vaccines authorized in the U.S.

Should previously infected individuals get vaccinated?

Dr. Makary says healthy patients with natural immunity need get only one shot, and even that may not be necessary. It is possible one shot will increase the longevity of the natural immunity. A University of Pennsylvania study of people previously infected with Covid found a single vaccine dose triggered a strong immune response, but a second dose had no appreciable increased response. Another study by New York’s Mount Sinai School of Medicine concluded “the antibody response to the first vaccine dose in individuals with pre-existing immunity is equal to or even exceeds the titers found in never-infected individuals after the second dose.”

Understanding the power and significance of natural immunity allows health officials to make sound, scientific recommendations on public health policy. Dr. Makary summarizes his opinion as follows: “Dr. Fauci said last Aug. 13 that when you have fewer than 10 cases per 100,000, “you should be able to open up safely and clearly.” The U.S. reached that point in mid-May. It’s time to stop the fear mongering and level with the public about the incredible capabilities of both modern medical research and the human body’s immune system.”

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