From CDC--But perhaps the biggest challenge is the time required to manufacture a new vaccine against an emerging pandemic threat. Generally, it has taken about 20 weeks to select and manufacture a new vaccine
. During the 2009 H1N1 pandemic, the first doses of pandemic vaccine did not become available until 26 weeks after the decision to manufacture a monovalent vaccine.
I did say “according to reports” - add this: they came from the CDC and are found somewhere in a thread about the virus