The US is nearing immunity from COVID-19
Despite media claims that “We Can’t Turn the Corner on COVID,” the numbers of COVID-19 cases, new hospitalizations, and deaths nationwide peaked and started to decline around the beginning of September. The combination of this milestone, new findings from the Centers for Disease Control and Prevention showing widespread levels of vaccination and natural immunity, and improved availability of treatments suggests that, outside of isolated pockets, COVID-19 is likely to become a diminishing health risk in the United States.
The CDC looked for evidence of prior infection or vaccination in the blood of approximately 1.5 million blood donors from around the country between July 2020 and May 2021. Based on the antibodies found in the specimens, they were able to distinguish between those who had been vaccinated and those with antibodies resulting from infection. As of the end of May, the combined vaccine and infection seroprevalence (indicating the proportion of the population with antibodies and some level of immune protection) was 83 percent for those 16 and older (children under 16 can’t donate blood). Over 20 percent had antibodies indicating an earlier infection and recovery. Based on the infection-induced seroprevalence, the researchers estimated that there were actually 2.1 infections per reported COVID-19 case.
Now, following the surge from the Delta variant, the number of confirmed COVID-19 cases (all ages) is over 40 million, or 8 million more than on May 31. Applying the 2.1 multiple from the blood donation study to the entire population results in a real number of cases and people with natural immunity of 84 million, or 25 percent of the population.
In addition, 177 million people are fully vaccinated, which is 53 percent of the total population and 34 million more than at the end of May. An additional 10 percent of the population has received a single dose, which provides some protection, albeit less than the full two doses.
While there is overlap because some previously infected people have been vaccinated, roughly 80 percent of the country has vaccine or natural immunity. Both types of immunity provide effective protection against COVID-19. The risk of breakthrough infections among the vaccinated is small, and when they occur, the vaccines continue to be effective in preventing serious illness, even for the Delta variant. The CDC also acknowledges that reinfection of recovered COVID-19 patients is rare.
Though a few vaccines induce a better immune response than natural infection, experts generally say that “natural infection almost always causes better immunity than vaccines.” This appears to be true with COVID-19.
A new study from Israel confirms that natural immunity to COVID-19 is superior to vaccine-induced immunity, even with the Delta variant. Between June 1 and August 14, when Delta was dominant in Israel, the risk of infections was 13 times higher for vaccinated people than for previously infected, unvaccinated people when either the infection or vaccination had occurred between four and seven months before. The risk for symptomatic breakthrough infections was 27-fold higher. While natural immunity did wane somewhat over time, vaccinated persons still had a six-fold higher risk for infection and a seven-fold higher risk for symptomatic illness than people infected up to ten months before vaccinations started.
An earlier study at the Cleveland Clinic of more than 52,000 health-care workers from December 16, 2020 to May 15, 2021 (just before Delta became dominant in the United States) found that both natural immunity and vaccine immunity provide good protection against infections. Not one of the 1,359 previously infected subjects who remained unvaccinated was reinfected. Their risk of infection was no higher than for vaccinated people, whether they were previously infected or uninfected.
Moreover, natural immunity thus far appears to be at least as long-lasting as vaccine immunity. Even before vaccines were widely available, studies indicated that four types of immune memory persist for more than six months after infection. The Cleveland Clinic results suggested that natural immunity provides protection against reinfection for ten or more months, leading the authors to conclude that previously infected COVID-19 patients are “unlikely to benefit” from vaccination. Another study found that convalescent individuals maintained immunologic protection for 12 months without vaccination, though protection could be enhanced by vaccination.
COVID-19 treatments have improved as well. Several versions of monoclonal antibodies have been authorized and are now readily available. These medicines are highly effective at keeping early COVID-19 from progressing, thus decreasing the risk of hospitalization or death by 70 percent to 85 percent, particularly for people at high risk of developing severe disease. Steroids and new, more effective ICU protocols have also led to lower COVID-19 mortality.
Of course, some super variant that escapes vaccine and natural immunity and is resistant to treatments could emerge, much as the emergence of Delta upset many forecasts. There is no way to predict such developments. But even the highly contagious Delta variant, which raised estimates of the percentages needed for herd immunity, did not evade vaccine and natural immunity protection. Delta morbidity and mortality has been heavily concentrated among those who had neither vaccine nor natural immunity.
Ending the COVID-19 pandemic doesn’t mean that the virus will be eradicated or that there will be no new cases. It means that serious illness and death resulting from infection with a virus that has likely become endemic will become rare. Our innovative, free-market economy has provided new vaccines and therapies in record time. Thanks to that, and to the undersold but important phenomenon of natural immunity, we are most of the way there.
Joel Zinberg, M.D., J.D., is a senior fellow at the Competitive Enterprise Institute and an associate clinical professor of surgery at the Icahn Mount Sinai School of Medicine in New York.
