"I don't need the vaccine; I've already had Covid and have superior natural immunity" is a popular refrain from some people who've been infected with Covid and, for that reason or another, are hesitant to get the Covid vaccine.
Does that argument hold up against an employer's vaccine mandate? According to two federal courts that recently examined the issue, the answer is a clear no. Kheriaty v. Regents of the Univ. of Calif. (decided 9/29/21 by a California federal court judge) and Norris v. Stanley (decided 10/8/21 by a Michigan federal court judge) each examined whether an employee was entitled to a preliminary injunction against their employer's vaccine mandate.
In each case, the Court sided with the employer and rejected the employees' pre-existing immunity arguments.
For example, the Norris court recognized that there is some science to support naturally acquired immunity from a previous Covid infection. But, there is also science to refute the effectiveness of naturally acquired immunity as compared to the effectiveness of the vaccines.
There is ongoing scientific debate about the effectiveness of naturally acquired immunity versus vaccine immunity. In creating its vaccine policy, Defendants relied on guidance from the CDC, FDA, MDHHS, and other federal and state agencies that have extensively studied the COVID-19 vaccine. Put plainly, even if there is vigorous ongoing discussion about the effectiveness of natural immunity, it is rational for MSU to rely on present federal and state guidance in creating its vaccine mandate. Thus, Plaintiff has failed to show that the MSU vaccine mandate does not meet rational basis. She is unlikely to succeed on the merits of her claim.
The Kheriaty court reached a similar conclusion.
These two defendants were public employers (state universities) that survived constitutional challenges to their vaccine mandates by those claiming superior immunity from a prior Covid infection. In the case of a private-sector employer, the employees of which lack any constitutional protections, the argument in support of the imposition of a vaccine mandate in similar circumstances would be even more compelling.
In sum, while there may be some scientific research to suggest that a prior Covid infection offers immunity to future infections rendering a vaccine unnecessary, there is equally compelling research that says the exact opposite. Thus, because the jury is very much out on this issue, an employer is free to establish whatever vaccine it wants and impose it upon those who previously suffered from Covid-19, without fear of being on the losing end of a judicial challenge by those with a claim of "natural immunity."