not that it’s entirely relevant to contract discussions, but the reason the original vaccines are no longer authorized is to simplify the vaccination schedule because almost everyone has antibodies to the original Covid variant (either through immunization or infection). They want people to get the updated versions and not use the ones that are geared toward the old variants.

https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-changes-simplify-use-bivalent-mrna-covid-19-vaccines



https://apnews.com/article/fact-check-covid-vaccine-shift-monovalent-bivalent-447335268816