NIH: There's More Proof COVID Vaccines Don't Affect Fertility

When the COVID-19 vaccine first became available in the U.S. in December 2020, it wasn’t long before misinformation started spreading on social media. Fears that the vaccines potentially cause infertility has proliferated widely on the internet. 

Now, a new study funded by the National Institutes of Health (NIH) is dispelling that myth. Epidemiologists at Boston University School of Public Health (BUSPH) in their new study show that getting vaccinated against COVID-19 does not make it harder to conceive and have a child. The study was published in the American Journal of Epidemiology.

“When the COVID vaccine first came out, we started hearing concerns that the vaccines could affect fertility," Amelia Wesselink, PhD, lead researcher and research assistant professor of epidemiology at BUSPH, told Verywell. "There isn’t any biological reason to expect the vaccine to affect fertility, but people clearly wanted data on time-to-pregnancy after vaccination, and we were in a good position to research this question using data from PRESTO, which is our online study of couples trying to conceive."

Vaccination Didn't Lead to Changes in Fertility

The research team studied more than 2,000 people between the ages of 21 to 45 years old. Study participants identified as female, living in the United States or Canada between December 2020 to September 2021.

Participants completed a questionnaire regarding:

• Income
• Education level
• Lifestyle
• Reproductive and medical histories
• Whether or not they were vaccinated against COVID-19
• If their partners had ever tested positive for the virus

Their male partners aged 21 or older were also invited to complete a similar questionnaire. The female subjects completed follow-up questionnaires every eight weeks until they became pregnant, or up to 12 months if they did not. 

Both male and female participants had a similar rate of vaccination: 73% of the women had received at least one dose of a COVID-19 vaccine during the study and 74% of men had at least one shot.

Researchers found there were no differences in the chances of conception if either male or female partner had been vaccinated, compared to unvaccinated couples. 

Among the couples studied, females who had received at least one dose of the vaccine before a given menstrual cycle showed a slight increase (8%) in conception, compared with unvaccinated participants. Females that were fully vaccinated—two doses of Pfizer or Moderna, or one dose of Johnson & Johnson—also showed a slight increase in conception (7%).

However, male participants showed few changes. Males that received at least one dose showed a slight increase in conception (5%). Fully vaccinated males conceived at the exact rate as unvaccinated males. 

Researchers say based on these results, vaccination status does not have a statistically significant effect on a couple’s or individual's chances of conception. 

“In our study, which included over 2,100 couples trying to conceive without fertility treatment, we found very similar time-to-pregnancy among vaccinated and unvaccinated couples,” Wesselink said. “We hope that these data are reassuring that the vaccine will not influence chances of having a baby, and that preconception is a great time to get vaccinated.” 

The study also found that testing positive for the COVID-19 infection overall was not associated with a difference in conception. However, couples had a slightly lower chance of conception if the male partner had been infected with COVID-19 within 60 days before the menstrual cycle—suggesting that COVID-19 could temporarily reduce male fertility. There was no impact if male partners had an infection at least 60 days prior.

Previous studies have also found that men who contract COVID-19 are more likely to experience erectile dysfunction than those who don't.

Long-Term Effects Are Unlikely

The researchers did not provide a conclusion regarding the long-term effects of vaccination on fertility, but they claimed it is unlikely that adverse effects on fertility could arise months after vaccination. 

“Based on what we know about biology and how the immune system works, there isn’t any reason to suspect that any effects of the vaccine—positive or negative—would emerge beyond a couple of months,” Wesselink said. 

But she adds her research team is working to analyze data to address questions and concerns regarding potential links between the vaccine and miscarriages or birth defects. 

“In the meantime, there are a handful of other studies out there that have shown no increased risk of miscarriage after vaccination,” Wesselink added. One NIH study found no increased risk of miscarriages back in September 2021.

The researchers are also looking at how vaccination can influence menstrual function and how COVID-19 itself can influence pregnancy health. 

“We hope that these data are reassuring that the COVID vaccine will not influence chances of having a baby, and that preconception is a great time to get vaccinated,” Wesselink said. 

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