TOKYO:Japan is scrambling to secure special syringes to maximise the number of COVID-19 vaccine shots used from each vial, but manufacturers are struggling to ramp up production quickly, raising fears that millions of doses could go waste.

Japan, with a population of 126 million, last month signed a contract with Pfizer Inc to procure 144 million doses of its vaccine, or enough for 72 million people, with the vaccination campaign set to start on Wednesday.

One vial is meant for six shots, Pfizer says, but it takes special syringes that retain a low volume of solution after an injection to extract six doses, while only five shots can be taken with standard syringes that the government has stored up in preparation for the inoculation drive.

"We are still trying to secure these special syringes," Chief Cabinet Secretary Katsunobu Kato said on Tuesday.

He did not directly answer questions when asked last week whether the shortage meant the number of shots Japan can administer would be reduced.

Both a Pfizer Japan spokeswoman and a Japanese health ministry official declined to say whether the contract to supply Japan with 144 million doses of vaccine by the end of the year is based on six doses being taken from each vial.

Inoculating its population swiftly is a top priority for Prime Minister Yoshihide Suga's government as he is determined to hold the Tokyo Olympics this summer after the Games were postponed for a year due to the coronavirus pandemic.

In an bid to minimize the amount of vaccine left unused in syringes and vials, the government is asking medical equipment manufacturers to boost output of the low dead-space syringes, but there are doubts whether that can be done quickly enough.

Nipro Corp, which runs a Thailand plant capable of making 500,000 units a month, said it planned to boost its monthly capacity to a few million, but that it would take up to five months to reach that goal.

"We are getting a request from the health ministry and we need to take some steps. But it's not something we can do overnight. It's another four to five months before we can ramp up sharply," a Nipro spokeswoman said.

Another major Japanese medical gear maker Terumo Corp said it had started developing syringes fit for extracting six doses from a vial, but that it was too early to say when it can start commercial output.

Although daily cases have been in decline in recent weeks in Japan after peaking in early January, Tokyo and nine other prefectures are still under the coronavirus state of emergency.

Japan has seen cases total around 418,000, with 7,042 deaths, according to public broadcaster NHK.