Not a lot. Notably, phase 3 trials of the various covid vaccines generally show that they work, and regulators have been reluctant to approve vaccines that appear to only marginally work (in fact, regulators have gotten stricter about this; in 2020 there was the general expectation that a vaccine that was 50% effective would work, but in practice a number of candidates hitting that sort of level have not gone forward, because the alternatives are so much more effective).