Spooked by a fast-spreading variant first detected in the UK, governments across Europe have imposed tighter and longer lockdowns and curbs.

They are pinning hopes on vaccines being rolled out across the continent.

But even when inoculations start en masse, the effects are not expected for months or until most people within a population get the shot.

The vaccine developed by US pharmaceutical company Pfizer with German partner BioNTech started being delivered in EU countries at the end of December.

US biotech firm Moderna began delivering its shot this week.

Yet about one third of the 27 EU governments cited "insufficient" doses at a video conference of health ministers on Wednesday, a person who attended the virtual meeting told Reuters.

Pfizer initially said deliveries were proceeding according to agreed schedule.

But later it said there would be a temporary impact on shipments in late January to early February caused by changes to manufacturing processes to boost production, not due to super-cold storage temperatures.

Belgium said it expected to receive only around half of the planned doses of the Pfizer vaccine in January due to a logistical issue.

Lithuania said it was told this week its supplies would be halved until mid-February.

Pfizer said modifications to the manufacturing process will require additional regulatory approvals.

"Although this will temporarily impact shipments in late January to early February, it will provide a significant increase in doses available for patients in late February and March," Pfizer said in a statement.

Pfizer and BioNTech have two contracts with the EU for the supply of up to 600 million doses this year.

They have agreed to deliver 75 million doses in the second quarter and more later in the year.

It was unclear how many doses can be distributed in the first three months.

Moderna has committed to delivering 10 million doses by the end of March and 35 million each in the second and third quarter.

Another 80 million doses are also to be delivered this year but without a clear timetable yet.

The Pfizer holdup aside, deliveries do not seem to be proceeding evenly across the continent.

Germany, with a population of 83 million, said it will receive nearly 4 million Pfizer doses by the end of January.

Romania, with a population four times smaller, says it expects to receive only 600,000 doses in the same period.

Bulgaria, with less than one tenth of Germany's population, expects to receive only about 60,000 Pfizer shots in January, in proportion much less than Germany.

A spokesman for the EU Commission said timetables for regions partly depended on contracts signed by each country.

It was not clear whether all governments had ordered their full allocation.

Turkey, not an EU member, said it had vaccinated more than 500,000 people in the first two days of administering shots developed by China's Sinovac Biotech, among the fastest roll-outs in the world.

"We are an experienced country in implementing nationwide inoculation programmes... We will win the battle with the pandemic together," Health Minister Fahrettin Koca tweeted.

Rising infections are turning up the heat on China to strengthen its pace of vaccination.

In the first nine days of January, about 4.5 million doses were given across the country exceeding the roughly 1.5 million given from July to November, Reuters calculations based on official data show.

By January 13, more than 10 million doses were given.

As of January 4, a unit of Chinese vaccine maker Sinopharm had shipped more than 10 million doses domestically while Sinovac had delivered more than 7 million as of January 10.

Indonesian President Joko Widodo received a first vaccine shot supplied by Sinovac Biotech to kick off a drive to inoculate two thirds of the country's 270 million population.

Unlike many countries, Indonesia intends to inoculate its working population first, partly because it does not have enough data from clinical trials on CoronaVac's efficacy on older people.

Australian Associated Press