Global clinical trials of an experimental vaccine developed with the University of Oxford has been halted, British drugmaker AstraZeneca Plc said Tuesday, citing "a potentially unexplained illness" in one of its volunteer participants.

A spokesperson for the Japanese arm of AstraZeneca said the pause would include Japan. The firm said last week that clinical trials of the vaccine candidate in the country have begun.

The company said its "standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee."

A packet of prescription drugs made by the pharmaceutical firm AstraZeneca on May 7, 2014 in Cambridge, England. (Getty/Kyodo)  

"This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials," a spokesperson for the British firm said.

According to a U.S. health news site, the phase three study in the United States had been put on hold due to a "suspected serious adverse reaction in a participant" in Britain.

Details of the illness are unclear, but the participant is "expected to recover," according to the site.

The British company had recently announced the start of the late-stage clinical trial of the vaccine in the United States that would involve up to 30,000 adults.

It has been testing the vaccine candidate in multiple facilities across Britain, Brazil, South Africa, the United States and Japan, targeting about 250 people aged 18 and older.

It also agreed in August with the Japanese government to supply 120 million doses of the coronavirus vaccine, and it plans to supply 30 million of those between January and March next year.

Japan also agreed to receive a vaccine by the end of June next year from U.S. pharmaceutical giant Pfizer Inc. and its German partner BioNTech SE.

As part of measures to fight the virus, the Cabinet decided Tuesday to use 671.4 billion yen ($6.3 billion) in reserve funds to purchase coronavirus vaccines currently being developed by drugmakers.

More than 500 new cases of the virus in Japan were confirmed Tuesday, pushing the cumulative total above 73,000, including about 700 from the Diamond Princess, a cruise ship that was quarantined in Yokohama in February. The death toll has exceeded 1,400.

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