Audio problem: When Michael bursts through the door at the hospital, Loomis fires his gun and Michael stabs him. He drops his gun on the floor and it makes no sound when it hits.
Audio problem: When Loomis shoots Michael in the opening here his gun sounds different from the previous movie.
Answer: I have read that, in early drafts of the script, the hospital was a health clinic, not a standard hospital. This would possibly explain why there are only a small number of patients, though it doesn't explain why there is a maternity ward, or why the mother brings her son there for emergency treatment.