To my knowledge, there has been no sustained or urgent work on a SARS vaccine since 2004.
In any event, the resistance of young people in King County (Seattle) to COVID-19 is still remarkable.
The COVID-19 outbreak at the Kirkland, WA, nursing home was one of the most virulent and destructive medical events in recent American history. At least 35 residents died, and almost 100 staff were infected during a two week period.
But, less than three weeks later, high risk individuals in King County are testing positive at a 13% rate (compare almost 40% for peak seasonal influenza), and our Case Fatality Rate is 6.4%, almost one half of the Italian rate.
My theory - COVID-19 has already mutated into a much more benign disease in King County.
You need to compare the death rate with the recovery rate. Some of the deaths are after prolonged illnesses. This guy was hospitalized March 8th or earlier, positive on the 13th, and died on the 29th (https://www.msn.com/en-us/news/us/henry-county-democratic-chairman-al-grimes-dies-of-covid-19-missouri-party-chair-says/ar-BB11SIzb).
Washington does have a different strain/mutation pattern than the rest of the country, at least as far as the genomes they’ve sequenced. It and the west coast had one set of strains out of China. Europe early on had a different set of strains (in blue) and the rest of the US and the world has shown more in common with Europe. https://nextstrain.org/ncov?c=clade_membership&r=division - if it doesn’t already show, set geographic resolution to “division” on the side to see within countries.
It looks like the European strain has expanded in Washington lately, so comparison to Italy may not be best. However, not that many strains out of Italy have been sequenced when compared to northwest Europe.