Feel free to disagree, but I did not say/mean that.

I think that well tested Vaccines certainly can prevent a disease, from most of the time to half of the time.

Based on the manufacturer's own research data, there is a lot of research and testing needed to make a vaccine work.
Most of the tests fail. Some tests even show bad side-effects. These side-effects depend on the type of vaccine. Example: some increase the severity of the disease.
The well researched vaccines do not work 100% either. They only work for a limited time. And some are only like 50% of effective, which means that some diseases can still spread even after vaccinations.

The reason for that is that vaccines only target a small part of the immune system.

In a normal scientific development we would be learning more about how to use the other parts of the immune-system to our advantage. Without causing bad side-effects. Yet the money and patents involved, causes the scientists to look for quick and dirty solutions. And the down-playing of disadvantages.

The corona vaccine allows to skip a lot of testing and run out experimental vaccines that likely have all kinds of side-effects. Likely, because the animal tests of such types of vaccines showed such side-effects. Due to the money involved I also expect a lot of P-hacking.