The myth that COVID-19 affects fertility first showed up on social media, when a fake report stated that the coronavirus spike protein was identical to another spike protein known as “syncitin-1,” which plays a key role in placental growth and attachment in the early stages of pregnancy. According to the fake report, the COVID-19 vaccine would teach a woman’s immune system not only to fight off the coronavirus, but also syncitin-1, causing problems with fertility.

In reality, the two spike proteins are completely different—they just happen to look somewhat similar in appearance. The COVID-19 vaccine doesn’t cause a woman’s body to reject the syncitin-1 protein; in fact, if this were true, then most women would already be infertile, as the common cold virus also has a very similar spike protein structure.