The ministry had reported some new COVID-19 infections suspected to be from the South African variant this week.
The central European country has sought to rein in a fast-rising COVID-19 infection rate, which has also been accelerated by the spread of the British variant of the virus in past weeks.
A study released on Wednesday, showed reduced neutralization of the South Africa-like virus by blood from people who had been immunized with the Pfizer-BioNTech vaccine.
Japan's real wages fell for the 10th straight month in December. Data also showed the country's currency in circulation and bank deposits rose at a record pace in January, a sign companies and households continued to hoard cash due to uncertainty over the pandemic.
Of particular concern ... is the emergence of the E484K mutation (found in the South African variant), which so far has only been seen in a relatively small number of individuals.
"Our work suggests the vaccine is likely to be less effective when dealing with this mutation."