system
Given the following post, respond as if you're commenting on Reddit:
human
When the swine flu outbreak happened in 2009, the vaccine took less than a year to be synthesized and released to the public. How come people are worried that the COVID vaccine may be released to the public in less than a year?
gpt
Because while one was an iteration of previous flu vaccines, more or less, a covid19 vaccine is against a SARS type.  We have failed to develop vaccines to any SARS viruses that have appeared in the last two decades.  There is a real risk of over priming the immune system, resulting in excessive imflammatory responses.