In order for something to have a potential side effect or complication, there has to be some biological way for this to happen. That is called biological plausibility. If someone said to you, “Eating ice cream causes you to grow an extra toe,” you would laugh and think it sounded crazy (and…you’d be right!).
Why is this? Because there is no biologic way to link ice cream to toe growth. Now let’s apply that same logic to the COVID vaccine.
Unfortunately, shortly after the first mRNA vaccine was approved by the FDA under emergency authorization, there was a (now removed) blog post that claimed the vaccine could lead to female sterilization. This post was written by a pulmonary medicine physician and a former Pfizer employee, so it went viral across social media.
The basis of this claim? That the vaccine contains a spike protein called syncytin-1. This protein is important in the formation of the human placenta, and they concluded that if the vaccine causes an immune response to this protein in the coronavirus, it would also impair future placental development, leading to infertility.
Unfortunately, this logic is incorrect, but that hasn’t stopped this myth from going viral on social media and causing a lot of concern over receiving the vaccine.
Here are the facts to help set the record straight:
The spike protein and syncytin-1 that is responsible for placenta formation share a very small segment of genetic structure.
They each code (make) a different protein. That means different antibodies bind to these proteins…which means no, the antibody we make after getting the COVID vaccine can’t attack our placenta cells. Think of a lock and key – the key is specific to the lock!
The mRNA in the vaccine is broken down as soon as it enters the muscle cells where it is injected. It does not cross the placenta!
In the Pfizer study, the number of pregnancies after receiving the vaccine was the same in those who received the vaccine as those who got the placebo.
We continue to see more data to show that receiving the vaccine does not affect embryo implantation or the development of an early pregnancy.
Sperm quality and number were not decreased or worsened in men who received the COVID vaccines as seen in a recent study.
Also, we have no data that the vaccine has led to any issues with male fertility. We do know fevers can temporarily decrease sperm production, so a post-vaccine fever may lead to this, but it is a much shorter fever than in someone who actually has COVID.
Lastly, there is no reason to delay trying to conceive or undergoing fertility treatments after receiving the COVID vaccine.
In conclusion, we have a lot of reasons why this vaccine won’t mess with a person’s fertility, and no evidence that it will—other than a misinformed, now-removed blog post that sadly went viral and shows us just how important it is to get our information from reliable sources.