The government says it plans to ensure staff at hospitals and nursery schools get two measles vaccines amid an outbreak of the highly contagious disease in Okinawa and other regions.

Since many people are catching measles at medical institutions, the Health, Labor and Welfare Ministry plans to urge hospitals to check the vaccination records of their employees, the government said Friday.

The ministry will also ask nursery schools to do the same.

In Japan, infants can get two vaccinations for free when they turn 1 year old and again before entering elementary school.

Ever since a March 20 measles case in Okinawa Prefecture, 94 more cases had been logged there as of Thursday. The virus is believed to have entered via travelers from Taiwan.

The outbreak has since spread to Aichi and Kanagawa prefectures and Tokyo. Symptoms include fever and coughing.

Measles is one of the leading causes of death among young children, the World Health Organization says. Exposure during pregnancy is associated with increased risk of maternal morbidity.

The government aims to have at least 95 percent of eligible children get the twin vaccinations, but the goal has been hard to achieve as the vaccination rate remains lower for the second shot.

Thirty-seven prefectures failed to meet the target in fiscal 2016. The lowest rate was found in Okinawa, at 89.8 percent.

Disease experts said at a meeting Friday that the low rate in Okinawa is likely behind the outbreak’s spread to other areas.

Another problem is that many people in their late 20s and 30s aren’t immune as they were given just one vaccination based on the program when they were kids.

Also Japan introduced a MMR (measles, mumps and rubella) vaccine in 1989 but was forced to ban it four years later after about 2,000 people suffered side effects that included aseptic meningitis.

This led to a revision of the Preventive Vaccination Law in 1994 that recategorized vaccination from being mandatory to just optional.

In 2008, over 10,000 measles cases were reported in Japan, but that has dropped rapidly due to the new prevention steps. In 2015, the WHO verified that Japan had eliminated measles. However, the experts at the meeting raised concerns about the new outbreak.

“If the measles infections continue to spread for a long time, it may nullify the status,” said Kazunori Oishi of the National Institute of Infectious Disease.