If I'm not mistaken, among Pfizer, AstraZeneca, Sputnik V, Moderna, medicine still havent discovered the best and successful vaccine?
The issue with virus is that they mutate in relatively short timespan. That is why we never have 100% effective vaccines against various infections causes as a result of viruses. Even in the case of COVID 19, the most effective vaccines (such as Pfizer and Moderna) only have a efficacy of around 95%. However, it is still initial stages and more and more vaccines are coming to the market with every passing month. Maybe some of these new vaccines can take the efficacy closer to 100%.