New data released from the Center for Disease Control reignites the formerly dismissed debate about natural immunity against COVID-19. Though the data indicate that prior infections provided greater immunity than vaccines alone, the CDC maintains that vaccination is the safest strategy against COVID-19. 

The CDC’s Data

In the first month of 2022, nearly two years after the pandemic began, the CDC released a study titled, “COVID-19 Cases and Hospitalizations by COVID-19 Vaccination Status and Previous COVID-19 Diagnosis — California and New York, May–November 2021.” As the title indicates, the study examined nearly 1.1 million people who were infected in New York and California over a seven-month period last year. 

Given this time frame, the Omicron variant and the effectiveness of booster shots are nonfactors in the data.

When comparing case rates between vaccinated people without previous infections and those who were unvaccinated with previous infections, a clear picture is painted. From the end of May through the first half of June, the data favored the vaccinated. 

However, this trend shifted with the arrival of the Delta variant near the end of June. By the first full week in October 2021, infection conferred greater immunity than vaccination. 

In California, case rates were only 6.2 fold lower among the vaccinated with no prior infections but 29.0 fold lower with the previously infected unvaccinated group (compared to the control group who were neither previously infected nor vaccinated). New York saw a similar trend with case rates only 4.5 fold lower among the vaccinated with no prior infection and 14.7 fold lower among the unvaccinated with prior infection.

As Agency France-Presse (AFP), an international French Press company, reported on the data, “By the week of October 3, vaccinated people who did not have prior Covid were three to four times (in California and New York, respectively) more likely to be infected than unvaccinated people with prior Covid.”

The CDC’s data also included hospitalizations, but only from California. Of the hospitalizations reported, AFP states, “vaccinated people who did not have prior Covid in California, were around three times more likely to be hospitalized than unvaccinated people with prior Covid,”  from October 13 to November 14, 2021.

The AFP also brought attention to potential “selection bias” that may have impacted the CDC’s study since it “excluded people who died, who were overwhelmingly unvaccinated.”

The CDC’s conclusion

While the data indicate that prior infections provided greater immunity than vaccines alone, the CDC concluded that “vaccination remains the safest strategy to prevent SARS-CoV-2 infections and associated complications.”

This conclusion, albeit accurate, may be a little disingenuous. Though it is a safer strategy to get vaccinated than to risk catching Covid, the CDC’s own data indicates that natural immunity alone is more effective at preventing infection and hospitalization than vaccination alone—as was the case during the seven months that were examined.

Johns Hopkins Professor rejects CDC’s conclusion 

According to Johns Hopkins School of Medicine Professor Dr. Martin Makary, the CDC “spun” its report to reach this conclusion. In his Wall Street Journal piece on the matter, he claims the CDC’s conclusion was based on the finding that hybrid immunity, the combination of prior infection with vaccination, was associated with a lower risk of catching Covid.

“But those with hybrid immunity had a similar low rate of hospitalization (3 per 10,000) to those with natural immunity alone,” Makary writes, referring to the same CDC report. “In other words, vaccinating people who had already had Covid didn’t significantly reduce the risk of hospitalization.”

The keyword in Makary’s statement is “significantly.” Though it is accurate to say that getting vaccinated post-Covid did not significantly reduce the risk of hospitalization, the data still seems to favor the vaccine-prior infection combination above all others.

Looking at the latest 14-day period in California’s hospitalization data, it’s clear that individuals who had only been vaccinated without prior infection had the highest rate of hospitalization. From October 31 to November 31, hospital rates among the vaccinated with no prior infections were 21.7 fold lower, but 69.7 fold lower among the unvaccinated with previous infections and 85.1 fold lower among the hybrid group.

This good, better, best pattern is observable among case rates in both states and hospitalizations in California—with most of the exceptions occurring before Delta’s arrival. 

Johns Hopkins study might strengthen the case for natural immunity

Continuing his argument for natural immunity, Makary stated in his article that, due to the National Institute of Health’s (NIH) “inaction” to investigate post-infection immunity’s duration, he and his colleagues at Johns Hopkins conducted their own study. 

“We found that among 295 unvaccinated people who previously had Covid, antibodies were present in 99% of them up to nearly two years after infection. We also found that natural immunity developed from prior variants reduced the risk of infection with the Omicron variant,” Makary asserts, though no link to the study was provided in his WSJ article. 

Stacking this Johns Hopkins study up against vaccine efficacy, Makary states, “the effectiveness of the two-dose Moderna vaccine against infection (not severe disease) declines to 61% against Delta and 16% against Omicron at six months, according to a recent Kaiser Southern California study. In general, Pfizer’s Covid vaccines have been less effective than Moderna’s.”

As the previously mentioned Johns Hopkins study cannot be found, the Lynnwood Times was unable to verify Makary’s claim that natural immunity lasts up to two years, though he does cite more studies suggesting that natural immunity lasts longer than vaccine efficacy. 

Israeli study favors natural immunity over vaccination

One such study was conducted in Israel and published on August 25, 2021. Its conclusion reads, “natural immunity confers longer lasting and stronger protection against infection, symptomatic disease and hospitalization caused by the Delta variant of SARS-CoV-2, compared to the BNT162b2 two-dose vaccine-induced immunity.” 

Similar to the CDC’s data, the Israeli study concludes, “Individuals who were both previously infected with SARS-CoV-2 and given a single dose of the vaccine gained additional protection against the Delta variant.”

Caveats to studies published on Medrxiv

However, the validity of this study is not immune to questioning as it was published to a free online archive called medrxiv.org, which houses complete but unpublished preprints in the medical, clinical, and related health sciences. 

Medrxiv’s “About” page states in bold letters, “Preprints are preliminary reports of work that have not been certified by peer review. They should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.”

This fact is reiterated below the study’s title, where it reads, “This article is a preprint and has not been peer-reviewed [what does this mean?]. It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice.”

It should be noted that the Kaiser Southern California study Makary cited regarding the waning efficacy of innoculation was also published to medrxiv.org and displays the same disclaimer. However, a December 2021 report from the New England Journal of Medicine came to a similar conclusion, stating that “immunity against the delta variant of SARS-CoV-2 waned in all age groups a few months after receipt of the second dose of vaccine.”

Of course, the waning efficacy of vaccines is also evident in the necessity of booster shots, which is why the CDC recommends boosters for elegible age-groups “at least 6 months after completing the primary series [of vaccination].”

The National Institute of Health on long-lasting, post-infection immunity

Coincidentally, exactly a year before Makary’s article was published wherein he calls out the NIH for being dismissive towards natural immunity, the agency released a study titled, “Lasting immunity found after recovery from COVID-19.”

Led by Drs. Daniela Weiskopf, Alessandro Sette, and Shane Crotty from the La Jolla Institute for Immunology, the study concluded that—while the levels of immunity components such as antibodies, T cells, and B cells varied among individuals—post-Covid infections did provide immunity lasting up to 8 months. 

As Dr. Weiskopf states, “Several months ago, our studies showed that natural infection induced a strong response, and this study now shows that the responses last. We are hopeful that a similar pattern of responses lasting over time will also emerge for the vaccine-induced responses.”

Even if Makary’s claim about two years of natural immunity doesn’t check out, the NIH’s findings still support his stance that natural immunity lasts longer than vaccine efficacy.  Given that post-Covid infections provide immunity lasting up to 8 months, natural immunity appears to be at least comparable, if not superior to innoculation—especially since vaccine efficacy waned after only a few months in the face of Delta.

Challenging the previously held consensus

Back in October 2020, an article in The Lancet titled “​​Scientific consensus on the COVID-19 pandemic” claimed that “there is no evidence for lasting protective immunity to SARS-CoV-2 following natural infection.” Rochelle Walensky, who is now the CDC’s director, was one of the publication’s co-signers.

The article was determinative for America’s vaccine-forward approach. “The evidence is very clear: controlling community spread of COVID-19 is the best way to protect our societies and economies until safe and effective vaccines and therapeutics arrive within the coming months,” The Lancet piece stated. 

Though this new data from the CDC may not cause an immediate about face, it is enough to challenge the previously held consensus, especially when over 146 million Americans have already been infected.

FEB 5 UPDATE: Since the timing of this article, the study Dr. Makary cited regarding natural immunity lasting up to two years has been made publicly available. You can view the study by clicking here.