The value of herd immunity in fighting Covid is indisputable.
Public-health officials in the U.S., unlike their counterparts elsewhere, have steadfastly focused on Covid-19 vaccines in fighting the pandemic, acting as if natural immunity following Covid-19 infection does not exist or is unimportant. The result: misguided policies that led to unnecessary job and educational losses and, quite possibly, excess mortality.
A new, systematic review and meta-analysis by the Institute for Health Metrics and Evaluation at the University of Washington, published in the British journal The Lancet, confirms what I and many others have long argued: natural immunity following Covid-19 infections is real, and “the level of protection afforded by previous infection is at least as high, if not higher, than that provided by two-dose vaccination using high-quality mRNA vaccines (Moderna and Pfizer-BioNTech).” Protection from past infection against reinfection by pre-Omicron variants was very high (85 percent) and remained high (79 percent) even after 40 weeks. Protection against reinfection was substantially lower for the Omicron BA.1 variant (45 percent) and declined more rapidly over time (by 36 percent at 40 weeks) than protection against earlier variants.
Fortunately, protection against severe disease and death appears to be maintained at a high level for all the studied variants. At 40 weeks, protection against severe disease remained at 90 percent for pre-Omicron variants and 89 percent for Omicron BA.1. In fact, the University of Washington researchers found that “protection against severe disease, although based on scarce data, appears to be durable up to more than 1 year” for pre-Omicron variants and the early Omicron variant BA.1.
These results confirm earlier studies. A Cleveland Clinic study of 52,000 employees reported in June 2021 that both previous infection and vaccination provide similar protection against Covid-19, and those with prior infection did not reduce their risk of reinfection by being vaccinated. It concluded that individuals with previous Covid-19 infections were “unlikely to benefit” from vaccination. When the authors published a follow-up in Clinical Infectious Diseases to account for the emergence of the more contagious Delta variant, they found that natural immunity was superior to vaccination. “Those with prior Covid-19 who remained unvaccinated had a cumulative incidence of Covid-19 that was significantly lower than that of those without prior Covid-19 who were vaccinated.”
Similarly, an Israeli study found that natural immunity to Covid-19 is superior to vaccine-induced immunity, even with the Delta variant. The risk of infections was 13 times higher for vaccinated people than for previously infected, unvaccinated people when either the infection or vaccination occurred four to seven months earlier. And while natural immunity waned somewhat over time, the vaccinated still had a sixfold higher risk of infection than people infected up to ten months before vaccinations started.
The advent of the Omicron variant, starting with BA.1 and progressing through multiple increasingly transmissible subvariants, has weakened immunological protection against the virus. But this development appears to affect both vaccine-based and natural immunity. These findings should be no surprise. Infectious-disease experts generally say that natural infection almost always confers better immunity than vaccines. It’s past time for public-health officials to say so publicly.
Anthony Fauci recently admitted that good scientific reasons always existed to believe that the Covid-19 vaccines would provide limited protection against infection and would last for only a few months. Fauci wrote that vaccines against respiratory viruses like the SARS-CoV-2 that causes Covid-19 usually provide “decidedly suboptimal” protection against infection and rarely produce durable, protective immunity because the viruses have short incubation periods, during which they rapidly replicate, cause illness, and spread to others—all before eliciting a systemic immune response needed for vaccine protection.
It soon became clear, too, that SARS-CoV-2, like the influenza virus, was prone to rapid mutations that would make vaccines prepared against one variant’s proteins less effective against those of later variants. Fauci acknowledged that the Covid vaccines “elicit incomplete and short-lived protection against evolving virus variants.” He also noted that the few vaccines that do prove successful in generating broader and longer-lasting immunity against systemic respiratory viruses—such as measles, mumps, rubella, and smallpox—are systemically replicating live-virus vaccines that fully encounter the host mucosal and systemic immune system. None of the Covid-19 vaccines falls into this category.
Natural immunity is more analogous to the live-virus vaccines. As the Washington researchers observed, immunity conferred by infection involves multiple immunologic pathways, including the spike proteins that the Covid vaccines target “in addition to other protein targets, that could lead to a more sustained immunity with increased protection against the various Covid-19 variants.”
Yet Fauci and other public-health authorities remained fixated on vaccines. From the earliest days of Covid-19 vaccine availability in December 2020 and January 2021, the CDC instructed everyone, regardless of previous infection, to get fully vaccinated as soon as possible. No attempt was made to prioritize those who had never been infected.
This meant that, in the opening months of 2021, when vaccines were still in short supply, shots were used to vaccinate people who were already immune instead of being directed to those without any immunity to Covid-19. Undoubtedly, some who lacked natural immunity from prior infection were unable to obtain a vaccine. How many contracted Covid-19 and died may never be known, but some of these deaths were probably avoidable.
Long-standing legal precedents give state governments and private entities the authority to impose vaccine mandates if they account for religious objections and medical contraindications. Several private companies, such as Google, Facebook, Netflix, and Lyft, as well as schools and universities and state and local governments, imposed vaccine mandates. Few of these institutions, if any, allowed exemptions for those who could demonstrate recovery from a previous Covid infection.
In one episode, George Mason University law professor Todd Zywicki challenged the university’s requirement that students, faculty, and staff verify their vaccination status or risk disciplinary measures, including unpaid leave, loss of merit pay, and termination of employment. Zywicki informed the university that he had recovered from Covid-19 and gained natural immunity, confirmed by several positive SARS-CoV-2 antibody tests, but the university insisted that he get vaccinated. The school backed down only when Zywicki sued, claiming a violation of his autonomy and constitutional rights.
Most people, though, are not law professors and could not readily challenge vaccination policies in this fashion. In October 2021—before the various Biden administration vaccine mandates commenced—the Kaiser Family Foundation reported that 5 percent of unvaccinated adults said that they had left a job because an employer required them to get vaccinated, accounting for 1 percent of adults nationwide. New York City alone fired 1,430 government workers who refused vaccination. Many of those unemployed and fired workers had likely already been infected with Covid and had natural immunity. They need not have lost their jobs. But many are still not allowed back, despite staffing shortages in essential jobs like firefighters and police officers.
In the 2021–22 school year, hundreds of colleges and universities instituted mandates, with many penalizing unvaccinated students by charging them thousands of dollars for regular Covid testing or by disenrolling them. Few, if any, recognized natural immunity. At the same time, states and school districts across the country imposed vaccine mandates of various types for K–12 students. Most have withdrawn these policies because of parental resistance (almost half of kids in this age group have not been vaccinated), judicial limitations on some mandates, and the realization that keeping students out of school would worsen the learning loss already caused by the pandemic. The District of Columbia is the sole remaining state-type jurisdiction with a vaccine mandate.
These mandates have never made much sense. Students in these age groups faced little risk of severe disease: children up to age 17 make up just 0.1 percent of Covid deaths and college/university students aged 18–29 just 0.6 percent. Most, if not all, of these deaths were of people with serious underlying medical conditions. Nor could mandates be justified as protection for older people whom these students would encounter—by the time they were mandated, the emergence of new variants meant that vaccines had already lost much of their effectiveness to stop infection and onward transmission.
Insisting that the young get vaccinated, particularly those already with natural immunity, exposed them to potential vaccine side effects. By April 2021, cases of myocarditis and pericarditis—inflammation of the heart muscle and surrounding lining—were reported following vaccination with mRNA vaccines. The complication is most common in adolescent and young adult males. Kids got myocarditis from vaccines that they didn’t need.
Unfortunately, some parts of the government have not gotten the news about natural immunity. The CDC still requires non-U.S. citizens traveling by air to the U.S. from a foreign country to provide proof of Covid-19 vaccination. Unvaccinated noncitizens with proof of natural immunity aren’t exempt.
This is not the practice in most other countries. The European Union’s Digital Covid Certificate allows proof of vaccination, a negative test, or recovery from Covid-19 infection within the last 180 days to facilitate access for travelers. The EU welcomed non-EU countries to join the certificate system over a year ago; thus far, 51 have done so. In the spring of 2021, the U.K. created the NHS Covid Pass and Israel the Green Pass for those with natural or vaccine immunity, in order to facilitate travel and entry to public places.
If the CDC’s travel policy insists on demonstrating immunity, it should also recognize natural immunity. Then again, the policy makes little scientific sense. There’s no rational reason to distinguish between U.S. citizens and noncitizens. If proof of vaccination/immunity is necessary to safeguard the country, every traveler should have to provide it. U.S. citizens are not, a priori, safer or more likely to be vaccinated than noncitizens. And why single out air travelers, as opposed to those coming by land or sea? Finally, it has long been apparent, with the emergence of new variants—each more contagious than its predecessor—that vaccines provide little protection against infection and transmission to others.
What explains public officials’ dismissal of natural immunity? CDC officials initially claimed that experts didn’t know how long natural immunity protection would last. But they didn’t know how long vaccine immunity would last, either, and we have seen the reasons to think that natural immunity would be better.
Officials might have worried that acknowledging natural immunity would undermine the push to get the public vaccinated. This assumed that Americans were incapable of understanding that there were two routes to immunity and that they could not be relied upon to document natural immunity before refusing a vaccine. Insisting that vaccines were needed for everyone, though, probably undermined public confidence and acceptance. People who knew that they had recovered from Covid-19 rightfully wondered why they needed a jab.
While announcing vaccine mandates on September 9, 2021, President Biden scolded those who had refused vaccines: “We’ve been patient, but our patience is wearing thin.” If the government is going to invade people’s autonomy by forcing them to accept an invasive medical procedure, the least it can do is ensure that the procedure will benefit them.
The least flattering explanation is that public-health officials did not want to acknowledge that people who questioned their need for vaccination, and who were more likely to be Republicans, might have a point. Biden criticized governors—all Republicans—who refused to require vaccination of schoolteachers and staff and threatened “if these governors won’t help us beat the pandemic, I’ll use my power as president to get them out of the way.” Yet his administration’s reluctance to acknowledge natural immunity probably widened the partisan divide, as it seemed more and more apparent that health officials were misleading the public and politicizing vaccination.
Public-health officials need to acknowledge natural immunity. A year and a half ago, the CDC estimated that nearly half the population had experienced a Covid-19 infection—and that was before the highly contagious Omicron variants hit. The number of previously infected Americans is now likely far higher. About 69 percent of the total population has completed the primary vaccine series, including 94 percent of those aged 65 and older. While there is overlap between the vaccinated and those who were previously infected, the large numbers in both groups suggest that most of the population has some sort of Covid-19 immunity by now. While that immunity is no longer especially effective protection against infection and transmission of newer viral variants, it does protect a large portion of the population from more severe illness and death.
No rationale exists any longer for penalizing those who, whatever their reasons, refuse Covid-19 vaccines—especially if they have already been infected.
Photo: Most infectious-disease experts say that natural infection usually confers better immunity than vaccines. (DMYTRO VARAVIN/ISTOCK/GETTY IMAGES)
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