I wrote last Sunday about the precipitous drop in COVID-19 cases over the past two months. I continue to believe that there will be ongoing reductions in infections as we move forward. However, in an opinion piece in the Wall Street Journal yesterday Marty Makary, a professor at Johns Hopkins Bloomberg School of Public Health, stated that he believed “herd immunity will be achieved by April” and that COVID-19 would be “mostly gone by April.” But his hypothesis is based on very “fuzzy math.”
In particular, he believes that immunity from prior infection is “much more common” than people have identified. He works back from “expected death rates” to suggest that the current overall case fatality rate in the U.S. is lower than “would be expected” because many more people have “natural immunity” to the virus. In addition, he argues that using antibodies to COVID-19 as a marker of prior infection greatly underestimates the number of people who have had infection, since others who were infected still have cellular immunity.
This leads him to say, “these numbers indicate that roughly two-thirds of the U.S. population has had the infection.”
Unfortunately, these arguments are more than a leap of faith. Most studies have shown that people infected with COVID-19 almost always make both antibody and cells that attack the virus (see figure). Within the first 90 days after infection, everyone who has had PCR positive COVID-19 also has antibody. This means all COVID-19 infections have been completely documented by antibody testing and are not “much higher than we believe” as stated by Dr. Makary.
More importantly, his calculations on improvements in the case fatality rate “from natural immunity” ignore the fact that treatment of COVID-19 patients has improved dramatically over the past year. This is the most important reason that the case fatality rate is much lower than initially projected. So again, the improved survival he bases his calculations on is not simply because there is “more immunity” around, but because the actual likelihood of dying from COVID in non-immune people is now lower.
I will stick to my assessment that roughly 1/3 of people currently have immunity to COVID-19, either by infection or vaccine. This is certainly enough to reduce the number of infections, especially since infection rates are higher in many hotspots on either coast and in the southeast, leading to higher levels of immunity in those areas.
However, this is not enough to “end COVID” in April. We need to continue to immunize every adult in the U.S. as quickly as possible. First, immunizing everyone will end concerns that vaccinated folks could still spread disease to non-immunized people.
It also reduces concerns about “variant” virus infections that can overcome “natural immunity.” This is because the immunity from the highly effective RNA vaccines is much better in protecting from the variant infections.
Given all this, COVID-19 won’t be gone, and the pandemic will not end in April. In my mind, the pandemic ends when we are back to normal and the masks and enforced restrictions totally end. This could be mid to late summer, but it will only happen if we aggressively immunize as many people as possible.