Kenneth Witwer addresses the idea that COVID-19 vaccines may cause fertility problems.

Specifically, a recent proposal says that the the endogenous protein Syncytin-1 (important for successful pregnancy and reportedly loaded into EVs) is identical or nearly identical to the COVID-19 virus Spike glycoprotein, and thus vaccines that train the immune system to target SARS-CoV-2 may also result in immune system attacks on Syncytin-1.

In fact, there is little or no identity of Syncytin-1 and SARS-CoV-2 Spike protein, with no epitopes (antibody targets) large enough to suggest cross-reactivity. There are several other reasons to discount this idea as well.

While anyone who is pregnant or considering pregnancy should consult with a physician about any concerns or vaccinations, the minimal or nonexistent identity of Syncytin-1 and the COVID-19 virus Spike protein suggests that cross-reactivity is unlikely to be a problem.