Japan has detected its first cases of the BA.4 and BA. 5 omicron subvariants of the coronavirus in airport screening, the health ministry said Thursday.

There were two cases of the BA.5 subvariant, found in a man in his 60s arriving at Narita Airport from Zambia and another man in his 60s arriving at Narita from Spain. Both individuals arrived on April 29 and were asymptomatic.

BA.4 was found in a man in his 50s flying from South Africa who arrived at Narita Airport on April 22. He is also asymptomatic, the health ministry said.

The three were fully vaccinated with three shots, according to the ministry.

The highly transmissible BA.4 and BA.5 subvariants have recently taken hold in South Africa, accounting for 70% to 80% of new infections there, said Tomoya Saito, director of the Center for Emergency Preparedness and Response at the National Institute of Infectious Diseases, noting that there has been no data showing that they lead to more severe symptoms.

All three individuals have completed their quarantine at a designated facility and have departed, the ministry said.