“Natural Immunity” to COVID and Vaccine Mandates

People who claim “natural immunity” from having had COVID and recovering should not be granted a pass from vaccination. I’m amending my case acceptance policy to decline cases of people who claim “natural immunity.”

When you get sick, your body sometimes produces antibodies that stick around in your system for a while and police against re-infection should the same pathogen show up later on. Only in a few cases does that alteration to your body’s natural immune system remain permanent. And it’s not always the case that your body keeps making those antibodies for very long. With COVID, more than one-third (36%) of people who have only “natural exposure” actualy develop antibodies. Liu, Russell, et al., (2021). Predictors of Nonseroconversion after SARS-CoV-2 Infection. Emerging Infectious Diseases, 27(9), 2454-2458 (36% of patients testing positive for COVID subsequently did not develop antibodies) (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8386781/). In other words, if there are eight people who say “I don’t need a vaccine, I got COVID already,” three of them are simply wrong.

There are consequences to this mistaken belief. For one thing, you’re more likely to get COVID again if you act like having it lets you skip vaccination. Unvaccinated COVID recoverees suffer reinfection at a rate of 2.34 times the rate of vaccinated recoverees (the so-called “breakthrough cases”). Cavanaugh, Spicer, et al.: Reduced Risk of Reinfection with SARS-CoV-2 After COVID-19 Vaccination — Kentucky, May–June 2021. MMWR Morb. Mortal. Wkly. Rep. 2021;70:1081-1083 (reinfection rate of recovered COVID patients who remained unvaccinated was 2.34 times the rate of vaccinated recoverees) (https://pubmed.ncbi.nlm.nih.gov/34383732/).

For another, unvaccinated people spread COVID more and faster than do vaccinated people. That’s true through droplets of water in exhaled breath, which masks help prevent, and it’s true through viral shedding in skin-to-skin contact. Chia, Ong, et al.,: Virological and serological kinetics of SARS-CoV-2 Delta variant vaccine-breakthrough infections: a multi-center cohort study, medRxiv 2021.07.28.21261295 (https://doi.org/10.1101/2021.07.28.21261295) and Pritchard, Matthews, et al., Impact of vaccination on new SARS-CoV-2 infections in the United Kingdom. Nat Med 27, 1370–1378 (2021) (https://doi.org/10.1038/s41591-021-01410-w).

There’s another study that hints at “natural immunity” alone providing more enduring immune responses than mRNA vaccines. The study claims that “natural immunity confers longer lasting and stronger protection” than the vaccines, and which also notes that “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.” Gazit, Shlezinger, et al., Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections, medRxiv 2021.08.24.21262415 (https://doi.org/10.1101/2021.08.24.21262415). As of the date I’m publishing this post, that study has not yet made it through peer review, although that hasn’t stopped the press from reporting on it as suggesting it’s somehow “unproven” that the vaccine is unnecessary for those who have “natural immunity.” That is not even what the study itself says — the study says that even if you have natural immunity, there is still a statistically significant benefit to being vaccinated on top of the natural immunity.

The science available to date doesn’t back up the claim that “natural immunity” makes vaccination superfluous. The science available to date says that three out of eight people who recover from COVID have no durable immune response to COVID at all. The other five still get even stronger immune benefits than they would without the vaccine. And it’s very unlikely that you know you have antibodies; you know that you had COVID and got better. Good for you; I’m sincerely glad you did get better! But that doesn’t mean you can skip the vaccine. Please get vaccinated anyway — if you’re right, now you know the vaccine won’t hurt you.

I will not take cases of people who seek an exemption from an employer’s vaccine mandate based on a claim of “natural immunity;” the scientific evidence does not back up the validity of such a contention. That means an employer is operating well within the realm of reasonability to enforce a vaccine mandate on an employee who has previously had COVID despite the possibility that employee now has some degree of “natural immunity.”

It seems that all I write about these days is COVID issues, but that’s because it’s a large majority of the calls and inquiries that I get (except calls on pending cases). Maybe one day we can get back to discussing sexual harassment or whistleblowing, but for now, it’s a whole lot of COVID. So I hope that this provides folks some insight and understanding of the interplay between the developing science and the law governing employees and employers.