COVID-19 Vaccine Does Not Affect Male Fertility—Here's What We Know

While the Internet has been rife with alarming stories that the COVID-19 vaccines could harm fertility, this fear is simply not true. According to the Centers for Disease Control and Prevention (CDC), "There is currently no evidence that any vaccines, including COVID-19 vaccines, cause fertility problems (problems trying to get pregnant) in women or men."

The COVID-19 vaccines have been rigorously tested for safety and efficacy—and they have not been shown to harm fertility. Moreover, the COVID-19 virus itself may have negative impacts on fertility and is known to increase the risk of pregnancy complications, findings that make it all the more important for everyone to get vaccinated.

SARS‐CoV‐2 RNA in Semen

One reason for initial concern about COVID-19's impact on fertility is due to a finding in a 2020 cohort study of SARS‐CoV‐2 RNA in semen. The study did not prove that the virus could be transmitted sexually, only that the virus was detected in the semen of people who were ill or recovering. This discovery resulted in speculation about whether COVID-19 could have effects on a fetus or on fertility.

Data are still being collected about COVID-19's impact on semen, pregnancy, and fetuses. However, evidence shows that pregnant people are at increased risk for severe illness from the disease. In addition, they are at risk for preterm birth and other poor pregnancy outcomes. So, concerns about the virus's effect on fertility and pregnancy are warranted. Moreover, research shows that the vaccine and booster are safe and effective during pregnancy.

There has also been speculation about whether or not the COVID-19 vaccine could affect sperm quality. Research has never supported or suggested this, and a study completed in 2021 offers empirical evidence to quell those concerns.

No Change in Sperm After Vaccine

A study at the University of Miami tested the semen of 45 participants, ages 18 to 50, prior to receiving a first dose of the vaccine and again 70 days after receiving the second dose. The study found no significant decreases in sperm parameters.

Since the vaccines contain mRNA and not the live virus, it is unlikely that the vaccine would alter sperm parameters. Interestingly, the study found a statistically significant increase in all sperm parameters. Before receiving the vaccine, eight study participants had low sperm counts. Of the eight, seven rose to the normal sperm count range after the vaccine; one remained low.

Researchers believe that the increased sperm parameters fell within individual normal variation and could be the result of the increased abstinence time before the second sample was taken (abstinence of three days was required prior to collecting the second sample).

Other research backs up these findings, showing no evidence of an adverse impact of COVID-19 vaccines on male fertility.

In a joint statement, the Society for Male Reproduction and Urology and the American Society for Reproductive Medicine said the only known impact of the vaccines on male fertility occurs if a fever happens after getting a dose. This may cause a short-lived decline in sperm health, something that can happen any time body temperature is elevated.

Impact of COVID-19 Infection on Male Fertility

Researchers are studying the potential adverse effects of COVID-19 infection on male fertility. Evidence of testicular damage has been found following COVID-19 illness, and further research is being collected on other impacts on male fertility post-infection.

"We were the first to demonstrate that the COVID virus, itself, can affect male fertility and be a potential cause for erectile dysfunction. We are now the first to examine if there is any impact of the COVID vaccine on male fertility potential, which we did not find," says Ranjith Ramasamy, MD, one of the authors of the University of Miami study.

Research has shown decreased sperm counts in some patients 72 to 90 days following infection with COVID-19. Ultimately, studies indicate the COVID-19 virus may pose a threat to male fertility, but the vaccine does not.

How Does the mRNA Vaccine Work?

Microbiologist and immunologist Andrea Love, PhD, has dedicated three podcast episodes to debunking vaccine myths, including one about female infertility. Dr. Love explains, “The current myth suggests that the immune response to the mRNA COVID-19 vaccines causes the body to attack syncytin-1, a protein in the placenta, which could lead to infertility in women."

Love continues, "The claim states that the SARS-CoV-2 spike protein, which is what the RNA in the vaccine encodes, is so similar to the placental protein syncytin-1 that it leads to cross-reactivity. Cross-reactivity means that our immune system can’t tell the difference between the two proteins and reacts to this placental protein as well.”

However, Dr. Love says that all proteins are made up of amino acids, and the mRNA vaccines don't have enough amino acid sequences in common to be mistaken for syncytin-1. “That .39% homology, or protein similarity, would never lead to a cross-reactive response. Proteins need almost complete similarity in order to be mistaken for one another by our immune system, therefore infertility could not happen.” 

Love also points to recent clinical trials refuting the claim. In fact, nine participants in the Pfizer-BioNTech vaccine clinical trial were dismissed because they became pregnant during the trial, with four of them being in the vaccine group.

Registries and trials in pregnant people are currently underway. BioNTech and Pfizer's phase 2/3 placebo-controlled trial will include 700 pregnant adults between 24 and 34 weeks gestation. The study is expected to conclude in August of 2022.  

What Is the Vaccine Made Of? 

According to the Centers for Disease Control and Prevention (CDC), the Pfizer-BioNTech vaccine contains the following:

• mRNA
• Lipids (fats)
• ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate)
• 2 [(polyethylene glycol (PEG))-2000]-N,N-ditetradecylacetamide
• 1,2-Distearoyl-sn-glycero-3- phosphocholine
• Cholesterol
• Salts and sugars
• Potassium chloride
• Monobasic potassium phosphate
• Sodium chloride
• Dibasic sodium phosphate dihydrate
• Sucrose

Love breaks these complicated ingredients down, “Despite the science terms, the mRNA COVID-19 vaccines have a quite simple formulation." They contain a sequence of:

• RNA, which is the template for our cells to manufacture the spike protein of COVID-19; in other words, the piece of the virus that our immune system recognizes and responds to
• Lipids to help transport and stabilize the RNA
• Buffers to normalize the pH and make it compatible with the pH of our bodies
• Sugar as a cryoprotectant, since the vaccine dosages are stored in freezer conditions.
  

While some of these ingredients may sound like scary chemicals, they're effectively harmless, says Love. They shouldn't deter you from getting the vaccine.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.