Vaccines are usually developed and tested over a period of 6-10 years.
If, and only if, after that much time, you don't observe any side-effects, then it is honest to declare it "safe". Everything else is just a lie to sell the product.
If, and only if, after that much time, you don't observe any side-effects, then it is honest to declare it "safe". Everything else is just a lie to sell the product.
The United Kingdom did authorise (some?) vaccines for emergency supply.