When do kids stop getting sick so much at childcare?

My kids are 3.5 and 1 just started preschool and daycare in September. They’ve been sick literally every week or every other week since. They just got over a cold last week and now they’re both sick again today with fevers and runny nose/coughs.

I feel bad they’re constantly miserable. And my husband and I are missing so much work having to leave and pick them up when they end up sick. When does it start to get better? Their doctor said after the first year but just looking for experience from other parents.