Let’s stop pretending that prior infection should not influence the decision to vaccinate.

Much has already been written about the CDC’s willful decision to ignore the relevance of prior infection, as if natural immunity simply did not exist. Most are aware that prior Covid-19 infection allows some degree of protection from future infection, with most studies suggesting this protection is north of 80% relative to someone with no immunity. It also leads to a greater immune response with first vaccination, which, in theory at least, could lead to better long-term protection, but also a higher rate of adverse effects. We are often told to “follow the science.” In this regard, there really is not much “science” to follow to endorse vaccination after infection.

Real world data is mixed; a recent study from Kentucky found two-fold additional protection to those with prior infection after full vaccination, while a larger study from the Cleveland Clinic showed no difference in re-infection rates between vaccinated and unvaccinated health care workers with prior infection.

Fortunately, we do have randomized controlled trial evidence to help shed light on the question. Unlike Johnson&Johnson, both Pfizer and Moderna tracked outcomes in their trials of those who had a history of Covid-19 infection before entering the placebo or vaccine arms. Moderna efficacy could not be evaluated due to having only one case in the placebo arm, while Pfizer showed a very modest 19% vaccine efficacy in the immunized group (vs 95% overall).

So - what does the science say? It says: barring new evidence, there is no clear benefit to immunizing those with confirmed prior infection. Common sense suggests there is a good chance these people would benefit from at least one (and possibly only one) shot as a “booster,” especially after 6 months or more have passed since the time of infection, especially with a more transmissible variant on the loose - but that’s common sense, not good quality data.

As a physician, I do think all but my lowest risk individuals with prior infection would have appreciable benefit from a single man-made “booster,” especially if they did not show evidence of antibodies, given the fairly robust correlation between a negative antibody test and risk of infection. However, I would not push if a previously infected patient opted to pass. As a citizen, I find it troubling that someone with prior infection could face an employer mandate to undergo vaccination against their will, given the slender evidence available.