There have been a lot of "science" documents that have been proved false, all in the name of profits.
People do not easily believe anymore. Which is good from a false news perspective but bad for any organisations who want to legitimately inform people of truth.
Perhaps the virus has mutated?
Do scientists use the latest virus to manufacture the vaccine? Its a live vaccine. Is it in time before another mutation?
Herd immunity is a myth. Everybody's immune system is different. It works on some but not others. You can never immunise 100% of the population, especially world wide. In a multipolar world where in a few short hours you can travel to a different continent. There are no checks to see if you have been vaccinated at the entry gates.