I am scheduled for Pfeizer next week and know about a dozen people who had it. None had any symptoms except for short numbness (minutes or maybe an hour) that is expected from any muscular injection. No fever at all and I do not see how it is possible.

Pfeizer is mRNA vaccine without the virus, it can only happen if the needle was contaminated. Or in very very very rare cases if your immune system over reacts (which it should not as mRNA should only teach T cells of the virus signature). If you had such reaction it would be a good idea to check your overall health as it is not a normal reaction to the vaccine.