Well if there were only 100 people, they'd probably have a fairly egalitarian society without strong notions of wealth or personal belonging. These groups operate as bands where it is in their best interest to keep everyone healthy. If one went off alone, they couldn't survive as they would most likely be predominantly foragers or horitculturists who supplement their diet by foraging. Agriculture and the luxury of settling down comes with numbers. Foragers would die if they were isolated. Because it only works as a group. So there would be no lone wolf gathering wealth--he would die.
So 100 people go off to find food, but only 20 find any, it's not a problem because everyone shares. Small bands don't resent this, it means survival.
A more likely scenario for a group of this number is they would probably break down into smaller bands. It's takes a fairly large area to gather food so they would spread out. In that case, they would trade members on occasion and most likely marry outside their own band.
So yes they would have universal health care as it was. Be it a doctor, or more likely, skilled herbalists, this would be a necessary service to the entire band. And it's not a bad life. Today there are still small bands of foragers, although they all interact to some degree with agriculturists and horticultorists, they do pretty good. They average 2300 calories for every man, woman and child. That's an abundance. So by supporting each other and caring about what happens to their neighbors, all members experience plenty. They also have surprisingly good health, because they are living the exact lifestyle that humans evolved to live. The foraging, egalitarian life style makes happy bodies and happy people.
So while others are trying to bend over backwards to deny that universal health care would apply to this group, they are trying to reconstruct this society in the context was what they have. It wouldn't be this way if only 100 people lived on an island. Every life would become more valuable and selfishnes would be unacceptable. No one could be a great deal richer than their neighbors because settling down to accumulate such wealth would lead to starvation.
That's my take anyway. I've studied it a bit.
NC