Historically they have had a very good result.
https://en.wikipedia.org/wiki/Vaccination................. Just like any medication or procedure, no vaccine can be 100% safe or effective for everyone because each person's body can react differently.[32][33] While minor side effects, such as soreness or low grade fever, are relatively common, serious side effects are very rare and occur in about 1 out of every 100,000 vaccinations and typically involve allergic reactions that can cause hives or difficulty breathing.[34][35] However, vaccines are the safest they ever have been in history and each vaccine undergoes rigorous clinical trials to ensure their safety and efficacy before FDA approval.[36]
Prior to human testing, vaccines are run through computer algorithms to model how they will interact with the immune system and are tested on cells in a culture.[34][36] During the next round of testing, researchers study vaccines in animals, including mice, rabbits, guinea pigs, and monkeys.[34] Vaccines that pass each of these stages of testing are then approved by the FDA to start a three-phase series of human testing, advancing to higher phases only if they are deemed safe and effective at the previous phase. ............
