Deutsche Welle (English edition)
COVID vaccine — the unfounded tale of infertility
It's a rumor that won't go away: COVID-19 vaccines lead to infertility in both men and women. Is there any truth to it? Or could it be possible that getting infected is worse?
Claims like "COVID vaccines make you infertile!" have been swirling around social media for months.
At first, it was only women who had to worry about their fertility after a coronavirus vaccine. And the proponents of the claim say they can explain it biologically.
They say that vaccines produce antibodies that not only attack SARS-CoV-2, the virus that causes COVID-19, but also a protein that's needed for a placenta to grow in the womb.
But scientists say that is a myth.
Take mRNA vaccines, such as those by the companies BioNTech-Pfizer and Moderna.
This is how the vaccines work: The vaccines hold a "blueprint," in the form of mRNA, for a bit of SARS-CoV-2, the virus that attaches itself to our cells and infects us. We're talking about the so-called spike protein that pokes out of the surface (or membrane) of the virus.
When the body reads that blueprint, the body produces a version of that spike protein itself and that kickstarts an immune response. It's important to note that the body does not reproduce harmful parts of the virus!
Based on those internal proteins, the body produces antibodies to fight what it thinks is an invasion by the SARS-CoV-2 virus. And that then gives you a good measure of protection against real attacks in the future.
'Completely unfounded'
The claims go on to suggest, however, that those antibodies attack another protein called Syncytin-1. It's that protein that helps placentas grow in the womb, and which is necessary for a successful pregnancy.
The reasoning of those people peddling the claim is that Syncytin-1 and the spike protein have a similar appearance.
But research indicates that actual similarities are very small, indeed.
The SARS-CoV-2 spike protein consists of 1,273 amino acids, while the Syncytin-1 protein has 538. Researchers have so far only found one sequence of five amino acids that shows any similarity between the two proteins. Even that sequence is not totally identical. And that's where the similarities end.
German researchers, such as Udo Markert and Ekkehard Schleussner of the University Hospital in Jena, Germany, have spoken out about the claims.
They point out that if it were true that an immune response produced by a vaccine can make you infertile, then it would also have to be true that a COVID-19 infection can make women infertile.
Ekkehard Schleussner heads the department of obstetrics at the university hospital. And Markert heads its placenta lab. Markert is also the president of the European Society for Reproductive Immunology.
"As far as we're concerned, in the field of placenta research and reproductive medicine, these widely spread claims are completely unfounded!" write Markert and Schleußner in a joint statement.
They advise every woman to get a vaccine to protect against a COVID-19 infectionc.
Also fear among men
But it's not just women who are worried. Some of the claims also target men, saying COVID vaccines negatively affect male fertility, as well.
But a study out of the United States suggests otherwise.
The researchers investigated sperm from 45 men before and after they'd had a mRNA COVID vaccine, and found no negative effects.
"We found no evidence to suggest any negative effects from a COVID vaccine on sperm among the men in our study," Daniel Nassau told DW.
Nassau, who is a urologist and co-author of the study, said he was confident that a larger number of participants would have delivered the same result.
Meanwhile, another author of the study, Ranjith Ramasamy, has written in The Conversation that the real threat to fertility is a COVID-19 infection.
Infection worse than vaccination
Ramasamy, who is a professor of urology at the University of Miami, writes that "contrary to myths circulating on social media, COVID-19 vaccines do not cause erectile dysfunction and male infertility."
And he and his team say they have proved it. They studied testis tissue collected from the autopsies of men who tested positive for COVID-19, along with that of those who died for other reasons.
Ramasamy says their results show that the virus can affect sperm production and hence fertility, and can also cause erectile dysfunction.
But Ramasamy says the results are not surprising. Other viruses, such as mumps and Zika, can cause inflammation in the testes which can affect fertility as well.
"The risk of infertility and erectile dysfunction increases with the severity of an infection," Nassau chimes in. "I strongly advise every man to get vaccinated."
to measure to really determine whether someone is immune or not. Presumably, the neutralizing antibodies play a key role — they bind the virus in such a way that it cannot infect any more cells."
But it is unclear how high the number of these antibodies has to be, he adds.
What T cells do
Not only antibodies are important in the fight against an infection. Once the virus has entered the cell, the antibodies can no longer reach it, because they themselves cannot go into the cell. So the virus can replicate.
"To fight that, our immune system has T cells; they are able to kill such virus-infected cells — in other words, we would rather sacrifice a few cells in our body, namely the infected ones, than give the virus the opportunity to multiply," Watzl says.
Both processes can be measured. In practice, however, it is more difficult to determine the number of T cells than that of antibodies. The T cell test is relatively time-consuming but quite useful.
"The antibodies alone don't necessarily tell you anything about how well you are protected," says Watzl: He says that a person might have hardly any antibodies and so could still become infected with the virus. "But the response of the T cells is so strong that the person doesn't get seriously ill," he says.
People with a high level of antibodies are probably well protected against the coronavirus, the immunologist says. But the reverse conclusion — that few antibodies mean no protection — is probably not true, according to him.
A matter of levels
Coronavirus antibody tests employ various measurement methods. Normally, laboratory tests use a clear standard stipulating a minimum to a maximum value. This allows a doctor to see whether levels are within the normal range. The levels have not yet been defined for the coronavirus, however.
So doctors approximate, with measured levels ranging from less than a hundred to several thousand antibodies. "If I am in the upper third or in the upper half, I probably have good immune protection. But I can't give you the exact threshold values yet," Watzl says.
It is not clear how quickly antibody levels drop, only that they do drop over time.
"It moves in two waves — if you look at the levels right after vaccination, you have the highest antibody level. In the first few months after vaccination, that level decreases relatively quickly. At some point, the whole thing settles at a certain value, and only drops very slowly from there," Watzl says, adding that scientists are familiar with this phenomenon from other vaccinations. "It appears to be true for the coronavirus vaccine, too; science just hasn't proven that yet," he says.
More is better
Some people who have been vaccinated twice have hardly any antibodies against the virus, so they are probably not properly protected, warns Watzl. Low antibody levels can be due to age or a suppressed immune system. Often patients need a third vaccination for the body to form antibodies at all.
Observations range from people who have many antibodies and are well protected and people who have too few antibodies and are poorly protected to people with few antibodies who are still protected.
The conclusion so far is that no one knows for sure. But Watzl is optimistic, emphasizing that "more is better."
"We don't know yet what the threshold levels are, and what level it takes to be protected," he says. "But we will get there someday."