The reduction will total between 85,000 and 100,000 doses, the national infectious disease agency SSI confirmed via its website.
That equates to a reduction of around 10 percent in the total delivery for the period compared with the original expected amount.
Around 42,000-50,000 fewer people will therefore receive vaccinations in the first quarter of 2021, since two doses are required.
SSI deputy director Ole Jensen said it was problematic that fewer doses than expected would be received.
“This is very unfortunate because we are at a very important point in the epidemic where it’s crucial to get moving with vaccination, so it’s a problem that we can complete vaccination of 50,000 fewer people with two doses than planned in the first quarter,” Jensen said.
As first reported last week, Pfizer has warned of a reduction in the number of doses of its Covid-19 vaccine to Denmark and other countries in the immediate future, as a result of work to expand capacity the company's factory in Belgium.
For Denmark, that means 30,000-35,000 fewer doses than expected this week, around half of what was expected.
But last week’s announcement was followed by reassurances that the total deliveries for the first quarter would be as expected, with a later increase in production making up for the immediate shortfall.
Ursula von der Leyen, the head of the EU Commission, was reported to have made that assurance after speaking to Pfizer CEO Albert Bourla.
Pfizer statements on the matter are related to the company now considering each vial it produces to contain six doses of the vaccine rather than the previous five, according to Jensen.
But Denmark already draws six doses from each vial and had planned vaccinations on this basis, he said.
Pfizer has also told SSI that there will be differences in the size of the reduction in deliveries between EU countries.
Jensen said that SSI and Danish health authorities, as well as the EU, are working to get Pfizer to deliver the quantities previously promised.
“We are doing all we can. We are in close dialogue with Pfizer whereby we are trying to get the vaccines we have planned for,” he said.
The Danish Health Authority said on Tuesday it had already adapted its vaccine schedule due to the delay.
As such, care homes residents awaiting their second dose of the vaccine will now be prioritised higher.