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February 02, 2022

COVID-19 vaccines do not have a negative impact on fertility, study finds

A growing collection of research points to the safety of vaccination among those trying to conceive, but some are still hesitant

Some people who are worried about getting vaccinated for COVID-19 cite worries of a potential impact on fertility as the reason. However, a new study published in the American Journal of Epidemiology found that there was no negative association between fertility and COVID-19 vaccines.

The study included 2,126 females from the United States and Canada who filled out a questionnaire every eight weeks. The list of questions included sociological information, demographics, medical factors, lifestyle changes, and partner information. Participants were enrolled between December 2020 to September 2021, and were followed through November 2021.

Researchers also collected information from 1,369 males, though all the men who took part in the study did so through their female partner.

In analyzing the information, researchers looked at the rate of fertility changes between those who were unvaccinated and those who had received either one dose or were fully vaccinated. They also tracked rates of infection during the study period and if any participants had previously tested positive for COVID-19. 

Of the participants, 74% had received at least one dose of a COVID-19 vaccine before the end of the study. Results showed that those who were vaccinated tended not to report a history of infertility, compared with those who remained unvaccinated. 

The study notes that there was "no meaningful association between COVID-19 vaccination in either partner and fecundability" – which is the probability of becoming pregnant after one menstrual cycle. The research adds to previous evidence from other studies that also showed no association between vaccination and infertility. 

"We definitely need to know more about the effects of COVID-19 itself on reproductive health," said Amelia Wesselink, the lead researcher on the study. "Our findings indicate that COVID-19 vaccination was not related to fertility are consistent with other studies from couples undergoing fertility treatment." 

Wesselink noted that the study did not include data on symptoms or severity of a COVID-19 infection, and further research on those topics is warranted. 

Where does the infertility myth come from?

In the introduction to the study, Wesselink and other researchers expand on what they believe is the source of the misconception. In December 2020, Wolfgang Wodarg, a German politician and doctor, raised concerns about the ingredients used in the Pfizer-BioNTech vaccine. 

Specifically, he noted one protein — syncytin-1 — which shares similar genetic instructions with COVID-19. It is also a component in the placenta of mammals. Wodarg and others were concerned that if the vaccine built antibodies against this protein, it could train the body to attack it in the human placenta, thus causing infertility. 

Researchers noted that the hypothesis regarding COVID-19 and infertility originated from a blog post, which made the initial claim, writing that "three studies have demonstrated the absence of anti-syncitin-1 antibodies after mRNA vaccination." 

Another common argument used by those who are vaccine hesitant is that changes in an individual's menstrual cycle could impact their fertility. This is understandable, given that some other vaccines do cause short-term impacts to the menstrual cycle, including the HPV, typhoid, and hepatitis B vaccines. 

However, the researchers found that most evidence on the impacts of COVID-19 vaccines on menstruation is anecdotal. The National Institutes of Health found that the COVID-19 vaccine was associated with a small, temporary increase in cycle length. 

In a survey by the New England Journal of Medicine in April 2021, 32% of respondents said that they would not get the vaccine, with 22% of those saying they would "definitely" not get vaccinated. 71% of those respondents said that they would not get vaccinated because of the side effects of the vaccine. 

While continued advancements in research have supported the understanding that COVID-19 vaccines do not cause infertility, health officials and doctors across the country have had to reassure the unvaccinated that there is no scientific basis for the concern. 

"I proactively address this rumor with my patients of reproductive age who have not been vaccinated," said Dr. Laura Morris, a family medicine doctor in the University of Missouri's health care system. "There is no plausible reason — no medical or scientific mechanism — for this vaccine to interact with a woman's reproductive organs or have any interaction with an egg that's been released or fertilized." 

The U.S. Centers for Disease Control and Prevention has guidance for those who are pregnant or looking to become pregnant and are curious about the impacts that COVID-19 vaccination or infection could have on the process. The CDC notes that there is no evidence to suggest that vaccination of any kind, including COVID-19 vaccines, cause fertility issues. 

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