When Does a Bird Sing?
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Kennedy quote shamelessly stolen from voat
Coronaviruses are responsible for about 10% of "common cold" cases. Most colds are due to rhinoviruses, of which there are over 100 serotypes. So too many to make a vaccine practical.
From the article it sounds like he had recent exposure and tested positive (likely PCR test). Not much cross positivity with other coronaviruses there.
polio is a single-strand, positive-sense RNA virus, and there is a vaccine