This report by Diaz et al1 is a follow-up of the larger controlled study by Gonzalez et al2 that documented a lack of semen parameter change in men who received COVID-19 mRNA vaccines. These patients were studied using semen analyses before and after vaccination. The current study extended the follow-up duration to a total mean of 10 months after vaccination. Again, no adverse effect of COVID-19 vaccination on sperm numbers was seen.
Although ACE receptors are a primary target of COVID-19 infection and are present at high levels within the testis, and although there have been anecdotal reports of detection of the virus in the semen of men with COVID-19, little was previously known about the overall effect of vaccination on semen parameters and fertility. Given the relatively low lethality of COVID-19 in young men (who are typically interested in fertility), any fertility risk associated with vaccination is considered important. These two studies that carefully and effectively screened men before and after COVID-19 vaccination provide highly reassuring information so that we can effectively counsel young men that vaccination should carry no measurable risk of adversely affecting fertility. Of note, at least anecdotal adverse effects from COVID-19 infection have been seen, as is common for men with any febrile illness, supporting the value of vaccination in limiting the chance of infection as well as the severity of infection.