Rising Measles Cases in Japan
Measles cases are increasing rapidly in Japan, raising concerns among public health officials and medical professionals. By mid-April this year, the total number of confirmed cases had reached 299, marking the second-fastest growth in the past decade. This surge is particularly alarming given that Japan was certified by the World Health Organization (WHO) in 2015 as being in a state of measles elimination. This certification means that no domestically established measles virus had been confirmed for at least three years. So why is this happening now?
The Spread of Measles
Measles is an extremely contagious disease, spreading about ten times more easily than influenza. It can be transmitted through the air, and simply being in the same room as an infected person can lead to infection. After contracting the virus, symptoms such as fever, coughing, and a runny nose typically appear within 10 days, followed by a rash that covers the body. In some cases, it can be fatal, with approximately one in every 1,000 patients dying from the disease.
According to the Japan Institute for Health Security, the cumulative number of measles cases had climbed to 299 by April 12. At the same point last year, the figure was 78, making this year’s rate nearly four times higher. The highest total in the past 10 years was 744 in 2019, and this year’s pace is second only to that.
Possible Causes of the Outbreak
One possible explanation for the rise in cases is the introduction of the measles virus by individuals returning from overseas or foreign tourists visiting Japan. The areas where patients have been confirmed support this theory. Tokyo has reported the highest number of cases, with 108 infections. When neighboring Kanagawa, Chiba, and Saitama are included, the four prefectures account for 183 cases, or over half of the total.
There have also been many cases in Aichi and Kagoshima prefectures, where cluster outbreaks have occurred. In urban areas with heavy foot traffic and high population density, the virus is thought to spread more easily through people arriving from abroad or those who have traveled.
Low Vaccination Rates
Another significant factor contributing to the outbreak is low vaccination rates. Vaccines are a powerful tool for preventing infectious diseases. In Japan, the current routine vaccination schedule consists of two doses: one at age 1 and another during the year before entering elementary school. Both doses are free because they are publicly funded. However, the two-dose schedule only began in April 2006. Before that, most people received only a single dose or none at all.
Additionally, vaccination rates have declined since the spread of the coronavirus. One dose of the measles vaccine provides 93% to 95% protection, while two doses increase this to 97-99%. To protect society as a whole from the spread of infectious diseases, vaccination coverage needs to reach at least 95%.
However, according to the Ministry of Health, Labor and Welfare, the rate of second-dose measles vaccination has not exceeded 95% since the COVID-19 pandemic and has continued to decline, falling to 91% in fiscal 2024.
Even after two doses, immunity can gradually weaken over time. In Japanese society today, opportunities to come into contact with the measles virus have decreased, which means immunity is not stimulated again, and people can become more susceptible to infection as adults.
Expert Opinions on Herd Immunity
Taito Kitano, chief pediatrician at Nara Prefecture General Medical Center, who specializes in infectious disease epidemiology, said, “At the root of this is the continuing situation in which Japan’s level of herd immunity is not sufficient to suppress measles transmission. When the level of herd immunity is not high, that population is constantly exposed to the risk of an outbreak, and that is probably what is now appearing in the form of rising measles cases.”
He emphasized the importance of taking measures to ensure that people—especially those with insufficient immunity—complete their vaccinations properly.
Cost of Vaccination and Calls for Government Support
One dose of the measles vaccine costs around 10,000 yen (about $64), sparking calls for state support. Tamae Hamaki, clinic director at Navitas Clinic Shinjuku in Tokyo, noted that many people seek vaccination due to fears about infection.
“People seeking vaccination began coming in around March this year, and the number has clearly increased since April,” she said. Visitors cited fears about infection, saying things like, “I heard the measles is spreading” and “A friend of mine came down with the measles.”
The vaccine generally distributed in Japan is the MR vaccine, which can prevent both measles and rubella. However, once people are past the period covered by routine vaccination, they must bear an out-of-pocket cost of around 10,000 yen per dose.
Hamaki added, “Given the state of society these days, 10,000 yen for a vaccination is by no means a light burden. Even if people are worried about the measles, or even if they are unsure whether they were vaccinated in the past, it would not be surprising if some hesitate to get the shot. To keep the number of patients from rising any further, it would make sense for the government to offer support, even on a temporary basis, such as covering vaccine costs with public funds.”
