You can hone your vaccines as long as you want when the disease prevalence is low. For example when you have archived a large enough immunity by unfortunate nat

You can hone your vaccines as long as you want when the disease prevalence is low. For example when you have archived a large enough immunity by unfortunate natural infection or by previous vaccines. During pandemic, vaccines are quickly developed like happened with H1N1 in 2009 that was last modern pandemic before SARS-Cov-2. Before that was Hong-Kong flu pandemic and before that Asian. In all cases the vaccine development was very fast. For Hong-Kong flu it was 4 months. For Asian flu it was a little longer. Development a vaccine for Swine flu took also few months but rapid production failed and the vaccine was delayed.