A group of researchers says its experiments show that three antiviral drugs approved in Japan are highly effective against the Omicron subvariant BA.5, which is spreading across the world.

The group, including researchers of the University of Tokyo and the National Institute of Infectious Diseases from Japan, released the results in the New England Journal of Medicine.

The researchers infected cultured cells with the BA.5 variant and administered a wide variety of drugs to the cells. They checked to what extent multiplication of the virus was suppressed by the drugs.

They say the three antiviral drugs for COVID-19 -- remdesivir, molnupiravir and nirmatrelvir/ritonavir -- were more effective against the BA.5 variant than the BA.2 strain.

They also say some drugs using antibodies were less effective against BA.5 than previously identified virus types.