system
Given the following post, respond as if you're commenting on Reddit:
human
How does a few people not getting vaccines cause an outbreak of the disease ?

Shouldn't the disease only affect the people that have not got the disease (and may be for those the vaccine isn't that effective) ?
gpt
With the vast majority of people being vaccinated, the spread of disease follows Herd Immunity. This is where the people who aren't vaccinated compared to the people who are vaccinated are so few, that the spread of the disease can be stopped/controlled and fizzes out. Once a larger percentage of the population decides to not get vaccinated, than the Herd Immunity starts to vanish, resulting in the ability for the disease to spread to increasing amount of people that are not vaccinated. The people who get vaccinated should be protected against, until a mutation/genetic-drift/-shift/different strain causes the need for a modified vaccination. Hope this answers your question!