As a Belgian, this is what we've heard and read:

- Pfizer stated on 15 Jan 2021 that they would produce 40% less (60.000 instead of 100.000 doses)

- This delay in production would we compensated in the weeks that follow. In February the production should be compensated.

- This was a temporary measure to scale up production after an extra order was made by the EU

The working group concerning the vaccine and it's distribution was to quote "not amused" by this news and wrote a sternly worded letter.

Source:https://www.vrt.be/vrtnws/nl/2021/01/16/versnelde-inenting-z... Text in Dutch.