Presumably there are parts which are patented and public (how the vaccine works in principle), and then there are parts which are not patented but a trade secret (how to actually manufacture it at scale). This kind of thing is very common.
similarly, companies like to lay minefields of patents around any given technology so that if they’re the market leader, they can slow down competition, but if they don’t have the winning version, they’re at least likely to get some royalties for the patents they have.
it’s perverse.