SAN DIEGO — Scientists have repeatedly demonstrated that the COVID-19 vaccines do not cause fertility issues, but mounting research shows the virus can.
This week, researchers in Brazil released biopsies on 11 men showing how the virus can infiltrate the testes and cause damage. All of the men died from COVID-19, and the paper has not yet undergone peer review.
It follows a study published this month on 120 Belgian men that showed both mild and severe COVID-19 infections could temporarily reduce sperm count and quality. Among those tested within one month of infection, 60% had reduced sperm motility, and 28% of the men had reduced motility after two months. The authors found no statistical differences between men admitted to the hospital and those treated at home.
Another study, funded by the National Institutes of Health, tracked 2,000 couples trying to conceive. It found a couple’s chance of success dropped 18% if the man had been infected with the coronavirus sometime in the last two months. After two months, the fertility rates of infected men returned to normal.
“Generally, the low sperm count or the infertility issues are within the first two or three months of infection because it takes about three months for a man to make new sperm,” said Dr. Mike Hsieh, the director of the UC San Diego Men’s Health Center.
Researchers are still studying how the virus can limit a man's fertility. Still, the new biopsies from Brazil show that infected cells can travel into the testes and cause damage directly. Inflammation in blood vessels and surrounding tissues can also impact hormone levels and sperm production, Hsieh said.
Scientists have theorized that fever caused by COVID-19 could also disrupt sperm production.
“Our testicle works best at two degrees below body temperature," Hsieh said. "So, when you get a high fever or a fever for a long period of time, that can impair the function of the testicle, both in producing sperm and testosterone.”
Changes in hormone levels and blood flow can cause erectile dysfunction, and research has linked COVID-19 infections to higher rates of ED. A study by a team at the University of Florida found men with COVID-19 were more than three times as likely to be diagnosed with ED. In all, about 5% of the male COVID-19 patients in their healthcare system developed ED.
In most men, fertility issues resolve, Hsieh said. But vaccination can greatly reduce these risks.
Studies by UC San Diego and scientists worldwide have found that vaccination does not affect fertility in either partner.
This story was originally published by Derek Staahl on Scripps station KGTV in San Diego.