Google My Business is responding to the economy's recent changes due to COVID-19 and providing businesses with a method of informing their clientele and online audiences they are no longer open or providing services. There are various examples of announcements to choose from including "Temporary Closure" or "In-stock, low stock, or out of stock announcements for high demand products".
Search Engine Journal states "COVID-19 update posts will appear at the top of a business’s profile in local search."
So you can continue to publish other types of posts, and the COVID-19 post will remain pinned to the top. As it stands, the shelf life for a COVID-19 post is the same as any other Google My Business post – 14 days."
You can learn how to post a COVID-19 announcement here.