We have known for some time that during covid-19 infection,
the SARS CoV-2 virus will infect the sperm producing cells in the testicles.
We also know that in some men this results in lower sperm quality. What we didn’t know
is whether the decrease was only in men who became very sick or only in men who had a
high fever. We also did not have information about how long sperm production is affected.
First, a little background.
It has long been known that exposure of the testicles to heat has an adverse effect on
sperm production. One source of heat is a fever. Studies have shown that fevers in men,
especially if it is a prolonged fever, can result in a temporary decline in their sperm production.
For example, when a man is infected with the flu virus, and develops a fever, the percentage
of moving sperm will decline. The severity of that decline is linked to the severity of the
fever with a maximal decrease of sperm movement seen 37 days later. After that, there is gradual
improvement so that by about 54 days after the fever, sperm movement has returned to normal.
Viruses can also affect sperm production without a fever.
One example is the mumps virus. This virus can infect the testicles directly
and cause swelling and inflammation. If this happens, about 10-15% of those
men will see their sperm numbers drop. In some cases the numbers could drop to zero.
SARS-CoV-2, the virus which causes Covid-19 can infect the testicles and cause a fever. A number
of studies have demonstrated a decline in sperm numbers or movement in men who developed Covid-19.
A new study has added to the growing amount of data about covid 19 infection and male fertility.
About 120 men were recruited for this study. These men were recruited because
they had tested positive for covid-19 not because they were having fertility problems.
This study showed for the first time that poorer sperm production occurred
in men with Covid-19 infection whether they had a fever or not.
In other words, it was the virus itself that caused the problem, not a fever.
Men with severe illness can also see lower sperm quality. However, this study showed poor sperm
production in men with mild covid-19 infection or even men who were unaware that they had a covid-19
infection just as often as men who became severely ill and were hospitalized
As a fertility specialist, there were two important questions that I had. First,
how commonly is sperm affected? Second, how long does this problem last? Remember with the flu,
about 10-15% of men developed sperm problems but it resolved within two
months. This new study showed us that decreased sperm quality is more common
with Covid. 37% of men had low sperm counts within 1 month of a covid-19 infection.
How long does it last? Between one and two months, about 29%
of men had low sperm counts. Between two and 6 months, 6% of men still had low sperm counts.
Sperm movement was affected even more commonly. 60% of men had low progressive motility within 1
month of their Covid infection. 37% still had low motility at 2 months but most concerning,
28% still had low motility between 2 months and 6 months later.
What have we learned? Covid infections result in a drop in sperm counts
in over ⅓ of men and those abnormalities are still present in about 1 in 20 men even 6 months later.
Even worse, about ⅔ of men will show a drop in sperm motility and half of those men still had
problems identified up to 6 months later. The most concerning factor is that these
sperm problems developed in men with mild infections and in men who had no symptoms.
Our InfertilityTV advice is to try to avoid getting Covid.
Covid vaccinations in men do not cause any change in sperm production
and can significantly reduce the chance for becoming infected