A new coronavirus variant has been detected in four travellers from Brazil's Amazonas state, Japan's Health Ministry said, the latest new mutation of the virus discovered.
A ministry official said studies were underway into the efficacy of vaccines against the new variant, which differs from highly infectious variants first found in Britain and South Africa that have driven a surge in cases.
No proof it is highly infectious
"At the moment, there is no proof showing the new variant found in those from Brazil is high in infectiousness," Takaji Wakita, head of the National Institute of Infectious Diseases, told a health ministry briefing.
Still, Brazil's Health Ministry said it has been notified by Japan's authorities that the new variant has 12 mutations, and one of them has already been identified also in the variants found in the United Kingdom and in South Africa. "It implies in a potential higher virus infectiousness," it said.
All travellers in quarantine
Of the four travellers who arrived at Tokyo's Haneda airport on January 2, a man in his forties had a problem breathing, a woman in her thirties had a headache and sore throat and a man in his teens had a fever, while a woman in her teens showed no symptoms, the health ministry said.
All travellers are in quarantine at Tokyo's airport, Brazil's Health Ministry said.
Emergency declared in Japan
After seeing a steep rise in coronavirus cases, Japan declared a state of emergency for Tokyo and three prefectures neighbouring the capital on Thursday.
Nationwide cases have totalled about 289,000, with 4,061 deaths, public broadcaster NHK said.
Japan hit with new virus wave
A history of vaccine controversies in Japan may cast a long shadow over the coronavirus jab roll-out, experts warn, even as the country battles a severe third wave of infections.
While vaccine hesitancy, and outright opposition, has been growing in developed countries in recent years, public suspicion dates back much further in Japan.
Slow vaccination drive in Japan
Even as millions in the UK and US are being inoculated against Covid-19, Japan has yet to approve a single jab, and vaccinations will not start before late February at the earliest.
This week, Prime Minister Yoshihide Suga said he would be among the first to be vaccinated, in an apparent attempt to bolster lukewarm confidence about the jab.
Just 60 percent of Japanese respondents in a December Ipsos-World Economic Forum survey said they want the vaccine, compared with 80 per cent in China, 77 percent in the UK, 75 percent in South Korea and 69 per cent in the US.
Mistrust over vaccine
The figure was still significantly higher than the 40 percent recorded in France.
Another poll, by Japanese broadcaster NHK, showed just half of respondents want the vaccine, with 36 percent opposed.
Mistrust in Japan dates back decades, with experts pointing to a vicious cycle of lawsuits over alleged adverse events, media misinformation and government overreaction.
Vaccine history in Japan
As early as the 1970s, class action lawsuits were filed against the Japanese government over side effects linked to smallpox and other vaccines.
And two deaths that followed vaccination with the combined diphtheria, whooping cough and tetanus shot prompted the government to temporarily withdraw the jab.
It was reintroduced shortly after with new rules but confidence did not recover.
Then in the late 1980s and early 1990s, cases of aseptic meningitis among children who received locally produced combined measles, mumps and rubella vaccines caused renewed outcry, prompting withdrawal of the combined jab.