Yes, she is required to have the vaccines BEFORE the K-1 visa will be issued. A medical exam is always required for a K-1 visa. However, if the K-1 medical exam is misplaced by the USCIS, then another medical may also have to be done. Make sure that she keeps a copy of it.
If she cannot take the vaccines or has previously been vaccinated, she needs to get documents from her physician before the K-1 medical exam, where she wants to try to opt out of the vaccines. If she is pregnant, then there may be something called titers [sic?] that can be done.
If she somehow 'refuses' to take the vaccines, she can be permanently denied a visa. There is no waiver for a refusal to take the vaccines except for a religious waiver or some medical verification that she will have an adverse reaction.
The above is general information and does not create an attorney-client relationship.