HONG KONG (CAIXIN GLOBAL) - Covid-19 infection could reduce male sperm count and lower sex drive, a new study from the University of Hong Kong (HKU) showed, while suggesting that vaccination can prevent such damage.

The findings are based on a study of testicular and hormonal changes in hamsters infected with the coronavirus and conducted by the university's microbiology researchers.

The study found that the hamsters suffered from acute decrease in sperm count and serum testosterone after four to seven days of infection. They also developed testicular atrophy with reduced testicular size and weight.

Previously, international studies found that male Covid-19 patients experienced testicular pain and lower sperm motility and lower sperm counts after recovery.

Autopsy results of some male Covid-19 victims showed that they had suffered from symptoms of orchitis, the inflammation of one or both testicles.

Professor Yuen Kwok-yung, chairman of infectious disease at the HKU's Department of Microbiology who led the research, said: "In managing convalescent Covid-19 males, it is important to be aware of possible hypogonadism (low sex drive) and subfertility."

Prof Yuen added that Covid-19 vaccination can prevent this complication.

Similar testicular changes were also found in hamsters infected with Omicron or Delta, two highly transmissible variants of Covid-19, the study said, noting that vaccination can prevent this testicular damage.

Researchers found hamsters who received two inactivated vaccine doses after three days of infection with the virus did not suffer from testicular injury while achieving immune protection.

They also found hamsters infected with a type of influenza virus showed no testicular infection or damage.

The hamsters in the tests developed "light pneumonia" from which they can recover without treatment, the study said.

The study has been accepted for publication in the peer-reviewed journal Clinical Infectious Diseases.

This story was originally published by Caixin Global.