Continuity mistake: When Michael's shown falling off the Wallace balcony in the opening scene it's on the front of the house not the back. Clearly this is a different house. (00:02:31)
Continuity mistake: At the end of part one, Laurie's stab wound was just a streak of blood and none on her shirt at all. When they bring her out to the ambulance, there's now a lot of blood on her shirt and streaks of blood on her arm. (00:13:20)
Continuity mistake: When Michael is stalking the hospital corridors there is a scene when he hides in the baby unit and is observing the Head Nurse berate Nurse Karen for being late again. The scene switches back and forth between a close up of the two nurses talking to a shot from Michael's perspective of them from inside the baby unit. In the close up the Head Nurse's body is facing Karen, from Michael's perspective her body is facing towards him on the other side of the nurse station. (00:30:20)
Continuity mistake: After Laurie wanders into a hospital room and unsuccessfully tries to use the telephone there are a series of shots cutting back and forth between the room and Laurie looking out into the hallway. In the shots from inside the room the telephone shifts position at one point. (00:59:01)
Continuity mistake: When Jimmy finds Nurse Alves dead on a stretcher and slips over in her blood pool, he hits the floor and there is a lot of blood on his face (especially near his mouth). A second later however, in an overhead shot, his face is clean. (01:03:25)
Continuity mistake: When Michael enters the Elrods' home and steals the knife, as he picks up the knife from where Mrs. Elrod had left it, there are several drops of blood that fall onto the lunchmeat, presumably from Michael's injuries from having been shot. A few seconds later when Mrs. Elrod walks back over to the lunchmeat and reaches for the knife and sees the blood, the droplet patterns are different.
Continuity mistake: At the end of the first Halloween, Loomis fires six audible shots from his gun (whether or not they all hit Michael is irrelevant). However, at the beginning of Halloween II, Loomis' gun can be heard firing off seven shots. Also the front view of the house from the first movie and second movie are two different houses. When Michael is shot he falls off the balcony which is on the side or rear. The second movie shows him falling off the front of the house. Different railings too.
Continuity mistake: After Ben Tramer gets hit by the police car, his body can be seen and heard slumping. In the next shot, he is pinned fully upright.
Continuity mistake: During the scene where Jimmy the paramedic finds Ms. Alves in the major surgery room on a stretcher with the blood completely drained from her body, while turning to walk out, he slips and falls back first in the pool of blood. Later, he finds his way to his car where Laurie had been hiding and attempts to get help. If you look closely, he still has the same shirt on, but it has no blood on it.
Continuity mistake: Jimmy walks across a huge puddle of blood before finding Mrs Alves dead on the stretcher. When he slips and is unconscious, you can't see any footprints, not even near the door where he came in.
Continuity mistake: Dr. Loomis shoots out the passenger window of the marshal's car, but it seems to be intact in later scenes, like when the woman is outside using the radio calling for help.
Continuity mistake: At the very end of the first Halloween, Loomis' first shot hits Michael while he is struggling with Laurie. A few seconds later, he is staring down Loomis and breathing very heavily. At the beginning of Halloween II, the scene is reenacted to reflect the ending of the first movie, but here you cannot hear Michael breathing at all after being struck by Loomis' first shot.
Continuity mistake: After Jimmy slips in Ms. Alves' blood, his position changes between the side camera shot and the above camera shot.
Continuity mistake: When Annie's dead body is rolled out on the stretcher her dad pulls the sheet back and revealing her slit throat. After a brief cut to him, when it cuts back to Annie the sheet covers her throat.
Continuity mistake: Notice how Michael is taking/reacting to being hit by the bullets at the conclusion of the first Halloween - you see him writhe in pain, his hand shake and grab near his side, and his body contort and literally twist before falling off the balcony - a believable shooting death scene. When the scene was re-enacted at the beginning of part II, all Michael does is lazily walk backwards and fall off.
Continuity mistake: When Loomis thinks he sees Michael but it is actually a drunk Ben Tramer in a mask, he runs after Tramer and pulls his gun. Brackett sees this and runs out of his patrol car, slams the door, and stops Loomis before Loomis gets off a shot. A few seconds later though, the car door is now open in the background.
Continuity mistake: When Michael stabs Nurse Jill in the back with the scalpel and lifts her off the ground, her shoes fall to the floor. A few seconds later, they are rearranged differently on the floor.
Continuity mistake: After the explosion and Michael is walking on fire, you'll notice he is right next to the burning stretcher. Then they cut to a scene of Laurie hiding behind a water fountain. In the next scene of Michael, he is now about 8 feet behind the stretcher walking towards her again.
Continuity mistake: Near the film's climax, the marshall is shown walking down a hallway by a soda machine and reacts to Laurie's screaming. He then makes a turn around to go see what was up. Several seconds (and many screams) later, Michael crashes through the door and the marshall is still running down the hallway by the same soda machine.
Continuity mistake: In the original film, the pumpkin at the Wallace's house was very small and fat, but in this film (which takes place the same night) you can see when all the cops and reporters are at the house that the pumpkin changed in size and the face is different as well.
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.