Science can prove danger but it can never prove safety. It is impossible to prove that something cannot happen! Even if not a single person in a study has an adverse reaction, there is always the possibility that someone else may be affected. What science can do, is weigh the risks versus the benefits. And when it comes to vaccines, there is just no question that the benefits outweigh the risks. By several country miles. Of course, nobody claims that there is zero risk associated with vaccines, just that the risk is minimal.
Kennedy and de Niro have a problem with thimerosal, a mercury-containing preservative that they claim can cause autism. This notion has been discredited over and over again. Furthermore, the argument that this dumbfounding duo puts forth - that the government warns against eating fish tainted with mercury while at the same time allowing mercury to be injected into people - is totally ludicrous. First, a single exposure to a trace of mercury is not the same as continuous ingestion, and second, the form of mercury in fish is methyl mercury which is far more toxic than the ethyl mercury released when thimerosal is metabolized.
The real point here is that Kennedy and de Niro have no expertise in this area but because of name recognition and celebrity worship people will be seduced by their nonsensical arguments. The offered prize money, though, is safe. It will never be given out. That’s because the challenge of proving that vaccines are safe is farcical. You can no more prove that vaccines are safe than you can prove that eating bread or any other food you choose is safe. De Niro should stick to acting and Kennedy to his white water rafting and falconry. Leave talk of vaccination to those who know what they are talking about.