Two Japanese pharmaceutical companies started clinical trials of their coronavirus vaccines on Monday.
In total, four firms are carrying out trials of domestically-produced vaccines in Japan.
Daiichi Sankyo said a total of 152 healthy adults are enrolled in the trial. It said researchers will check the safety of its vaccine and whether antibodies are created, as well as try to determine how many doses should be recommended.
The Daiichi Sankyo product is of the same type as the Pfizer vaccine that uses mRNA. Inoculations with the Pfizer vaccine are already underway in Japan.
KM Biologics also started a clinical trial of its vaccine, with 210 healthy adults taking part. It is an inactivated vaccine, of the same type as influenza shots.
The health ministry says the two have become the third and fourth firms to carry out such tests with domestically-developed vaccines, following Shionogi and AnGes.