In some countries there's a formal labor law for doctors notes after X days that is known by all and which might mean your doctor checks and registers the case(?) in other places it is total discretion if a manager demands a note but rarely does in places that aren't shift work oriented.
Given two people who WFH the vaccinated one can conveniently eat in a restaurant and go to the gym while the unvaccinated needs to get take out or is getting regular tests. I think vaccinated people have much more interaction with the virus unmasked in an indoor environment but much less likelihood of ever being tested when having light or no symptoms.
In some countries (the US is an example); there's a social class aspect to vaccination; highly educated people are more likely to be vaccinated, and also more likely to work from home.
However, if this was a big factor you'd expect vaccines to appear dramatically less effective in near-universal-vaccination countries, like Portugal. That doesn't seem to be the case.