No, We will not have Herd Immunity by April

Dr. Marty Makary is a brilliant physician and communicator. I am a fan. However, he just wrote an Opinion piece for the Wall Street Journal entitled, “We’ll Have Herd Immunity by April.” He could not be more mistaken.

He points to the significant decline in cases, his projection that 55 percent of Americans have natural immunity from past infection and an assertion that 15 percent of Americans have been vaccinated.

So, let’s understand why we are nowhere near herd immunity:

1. Yes, cases are down. They are down following an all-time high surge that just two months ago was threatening to overwhelm our health care system. Cases always come down after a surge, and holidays are notorious for creating surges in cases due to travel and extended families and friends getting together.

So, are the cases down at a level that would suggest the pandemic is coming under control? No. Our current 7-day moving average of daily new cases per 100,000 in the U.S. is at 23.9. We have had 3 spikes or waves in the U.S. of cases. Our first was in March of 2020 at the onset of the pandemic. You might recall that cases were so alarming back then that many states implemented stay-at-home orders or lockdowns. So, what was the 7-day moving average of daily new cases per 100,000 in the U.S. at the peak of that first spike or wave? 9.8.

Our second spike or wave of cases was far greater and occurred during the summer. Well, what about the second spike or wave? What was the 7-day moving average of daily new cases per 100,000 in the U.S. at the peak of that wave? 20.4.

As you can see, cases have not even come down to the highest point they previously were with our first two waves. So, it seems premature to be declaring victory. We have all become a bit numbed to the numbers. We are currently at levels of disease transmission that last year would have been quite alarming. But, with each higher wave of cases, hospitalizations and deaths, we have become so conditioned to the large numbers that we think when cases are coming down from an all-time high that we must be on the home stretch.

So, how do we put these numbers in perspective? The Harvard Global Initiative sets 25 daily new cases per 100,000 as the level at which lockdowns, stay-at-home orders, etc. are indicated. Remember the White House Coronavirus Task Force chaired by Vice President Pence? The number they used for when transmission was out of control and required significant restrictions – 14. So, I think Dr. Makary is painting a far rosier picture of where we are than what the data shows.

Here’s additional perspective. Remember back at the beginning of the pandemic when our objective was to avoid community spread? Community spread was when there was so much spread within a community that we could no longer identify the source of infection for people who tested positive for COVID. Translated into daily new cases per 100,000, community spread is 1 – 9. Over 9 is accelerated community spread. That is where the U.S. is now.

So, if we were to get to herd immunity, what level of daily new cases per 100,000 would that be? Answer – less than 1. As you can see, we are nowhere close to this.

• Dr. Makary projects that 55 percent of the American population has been infected. The problem is there is no way to prove or disprove that assertion. No serologic survey in the U.S. would lead us to that conclusion. Dr. Makary rightly points out that people may have immunity even without measurable antibodies due to T-cell mediated immunity. This is true, but again, doesn’t help us get to the number of people who have immunity, because we cannot routinely test for T-cell mediated immunity.

The CDC has made its own projections about how many Americans have been infected (and then presumably are immune, however, we are not inclined to believe that everyone who has been infected does have persistent immunity). Their projection is 83,111,629. Using the most recent U.S. population number, that would mean 25 percent of Americans have been previously infected and might still be immune – less than half of what Dr. Makary projects. We can’t know who is right.

But Dr. Makary goes on to make a statement that we know is incorrect. He states, “Herd immunity has been well-demonstrated in the Brazilian city of Manaus, where researchers … reported the prevalence of prior COVID-19 infections to be 76%, resulting in a significant slowing of the infection.” You may recall that Brazil did have a massive explosion of COVID cases at the beginning of the pandemic in the spring of 2020. Manaus was hit particularly hard. In less than 10 days, the health care system in Manaus was overwhelmed. Patients were turned away from hospitals bursting at the seams with COVID patients. Many who died of COVID were placed in mass graves.

Mathematical projections of the numbers of people who would have to be immune in a population (a herd) to make it difficult for the virus to circulate in the herd and infect those few who are vulnerable was 60 percent and virologists and our own public health experts anticipated that the actual threshold for herd immunity might be 60 – 70 percent. When scientists determined that 76% of the population of Manaus had been infected, the highest prevalence of any place in the world that I am aware of, it is true that we certainly presumed that Manaus likely had achieved the level of infection necessary to achieve herd immunity. But, where Dr. Makary is mistaken is his assertion that herd immunity was “well-documented in the Brazilian city of Manaus.” In fact, subsequent events disproved herd immunity in Manaus.

Recently, Manaus went through a new surge in COVID cases overwhelming their hospitals, not in 10 days as previously, but now in 24 hours. This is a strong argument against herd immunity. Hospitals quickly ran out of oxygen. Some hospitalized patients died because there was no supplemental oxygen to administer. Many more people died at home due to the lack of hospital capacity. This second wave was greater than the first. This is not consistent with herd immunity.

Now, one could argue that perhaps Manaus had reached herd immunity, but people’s immunity from previous infection with prior variants had waned, and they no longer maintained herd immunity. True, that may be the case. However, if true, that should also cause us concern in the U.S. that not all the people Dr. Makary believes have previously been infected remain immune. One could also argue, well the people of Manaus probably developed herd immunity to the D614 or D614G variants that were common at the time, but they just were not immune to the new variant, P.1. Also, very possibly true. But, in either case, what good is herd immunity, then? In the U.S., we have at least four new variants of concern (more variants than that, but I am just referring to the variants that have us worried). And, in either case, then why should Dr. Makary convince us that the U.S. will achieve herd immunity by April and all will be fine?

• Dr. Makary asserts that 15% of Americans have been vaccinated. However, based on the latest numbers reported by the CDC, only 5% of the American population has been fully vaccinated, and with the most generous interpretation of the percentage of Americans “vaccinated” to include those who have only received their first dose, it would be 12.7%.

I am sorry to tell you that I don’t perceive any situation by which the United States achieves herd immunity by April of this year. The previous mathematical projection of 60 – 70% of people needing to be immune in order to achieve herd immunity has been revised upwards to perhaps 85% because models predict that a far more contagious variant will become dominant in the United States in March. In calculating the percentage of population necessary to achieve herd immunity, everyone who can be infected and transmit the disease must be included in the denominator. It is estimated that 24% of the American population is under the age of 18. There currently is no approved vaccine for children under the age of 16 and it is unlikely there will be until at least summer. If the percent of the population under 16 is 20%, then already, if everyone else in the country over the age of 16 has been infected and/or received a COVID vaccination, we would only get to 80% immunity. But, then again, we know that surveys tell us something on the order of 30% of Americans are either vaccine-hesitant – they want to wait 6-12 months before they get vaccinated or they are telling us that they will not get vaccinated.

Let’s march on. We will get there; we just won’t get there by April. Please don’t let your guard down. Stay home if you are sick. Get vaccinated if and when you can. Avoid gatherings of people other than those you live with, particularly indoors. Wear a mask when you are around people you do not live with. Wash or sanitize your hands often and every time after touching surfaces that are in public spaces. Keep a physical distance from others of at least 6 feet.

I haven’t posted many blog pieces lately, and that is because I am writing a book. But, I worry that you are hearing and reading a lot of false or misleading information right now, so I am going to try to write more often. As the co-author of the book we are working on often says, “Stay positive and test negative!”