Health Care

Vaccine Skeptics’ Misplaced Infertility Concerns

Emergency medical physician Thomas Krajewski wears a mask as he holds his baby Cal with his wife Genevieve after finishing his shift amid the coronavirus outbreak in New Orleans, La., March 27, 2020. (Kathleen Flynn/Reuters)
Addressing the latest flawed theory on the long-term health effects of coronavirus vaccination.

As of Thursday morning, roughly 32 million doses of the FDA-approved Pfizer and Moderna mRNA vaccines have been administered in the United States, and 8 percent of the population has been inoculated against COVID-19. At some point, the more-traditional adenovirus vaccines developed by AstraZeneca and Johnson & Johnson will join the Pfizer and Moderna vaccines on the open market. This should speed up the pace of distribution, since the AstraZeneca and Johnson & Johnson vaccines are cheaper and don’t have the same storage needs as the other two. But it won’t necessarily speed up the pace of inoculation, because a significant proportion of Americans remain wary of the vaccines: An Axios-Ipsos poll conducted between December 12 and January 11 showed that only 60 percent of Americans plan on being vaccinated as soon as the option becomes available to them.

I have previously written on vaccine skepticism, addressing both the safety concerns and ethical reservations that some have about the coronavirus shots. These concerns are only natural, given the unprecedented speed with which the vaccines were produced and the dearth of long-term studies on them. But as I noted in my previous pieces, there is no evidence to suggest the vaccines are dangerous, and all of the theories meant to explain why they would be are, at best, unsound. Outside of the extremely rare — somewhere between two and three cases per million vaccinations in the case of Moderna, and around six per million for Pfizer — severe anaphylactic reaction, there have been no major health issues associated with the vaccines. On-site monitoring has ensured that no one has died as a result of such a reaction or any other vaccine-related cause.

Now, however, longer-term health worries have begun to take center stage among vaccine skeptics. Fertility in particular has become a lightning rod. It has been rumored that Pfizer and Moderna’s vaccines can prompt pregnant women’s bodies to “attack” the placenta in the same way that it prompts them to attack the disease.

There are no recorded cases of this having happened; 23 women enrolled in vaccine trials became pregnant over the course of the trials, and the only one to suffer a miscarriage was given the placebo, not the vaccine. But to clear up the confusion that has led people to worry that it might happen, I’d like to delve into the science of the Pfizer and Moderna vaccines a bit.

Let’s review how the new mRNA vaccines work. Here’s how the Centers for Disease Control and Prevention (CDC) explains them:

To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines . . .

COVID-19 mRNA vaccines give instructions for our cells to make a harmless piece of what is called the “spike protein.” The spike protein is found on the surface of the virus that causes COVID-19.

COVID-19 mRNA vaccines are given in the upper arm muscle. Once the instructions (mRNA) are inside the muscle cells, the cells use them to make the protein piece. After the protein piece is made, the cell breaks down the instructions and gets rid of them.

Next, the cell displays the protein piece on its surface. Our immune systems recognize that the protein doesn’t belong there and begin building an immune response and making antibodies, like what happens in natural infection against COVID-19.

At the end of the process, our bodies have learned how to protect against future infection. The benefit of mRNA vaccines, like all vaccines, is those vaccinated gain this protection without ever having to risk the serious consequences of getting sick with COVID-19.

The confusion concerning fertility and the coronavirus vaccines stems from the fact that the protein “spike” that the mRNA causes our cells to produce shares a sequence of five amino acids with syncitin-1, a protein found in placentas. But the amino-acid overlap between the spike protein and syncitin-1 is extremely small relative to the size of the protein, extremely common, and not nearly significant enough to cause an adverse physiological reaction to the placenta.

For some perspective, consider that hemoglobin, the protein that carries oxygen in our blood supply, happens to share six amino acids with the protein spike. Tens of millions of doses of the two mRNA vaccines have been administered across the globe, and there have been no incidents of inoculated bodies’ attacking the hemoglobin in their own blood.

What’s more, if this threat were credible, we’d expect to have seen women who’d contracted the coronavirus and possessed its antibodies experience fertility issues, which they haven’t. We’d also expect to have seen evidence that getting the virus would pose just as great a risk to fertility as getting the vaccine, which we haven’t.

It’s no crime to wonder if there will be adverse health effects associated with these vaccines, which were produced with historic speed. But again, there’s not a shred of actual hard evidence to suggest that any of the specific concerns raised about them are true, and that includes the claim that they could render women infertile. Well over 2 million people have died globally in the coronavirus pandemic, including over 450,000 Americans. The number of known deaths and infertility cases caused by the Pfizer and Moderna vaccines is the same in the United States as it is everywhere else: zero.


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