Multiple reasons explain why the vast majority of medically trained physicians support vaccinations. Physicians receive the majority of their training during medical school, which is heavily influenced by pharmaceutical companies and government institutions such as the Centers for Disease Control and Prevention (CDC).
Both pharmaceutical companies and government organizations support a misguided agenda in which vaccinations are promoted as a primary tool to prevent disease. Practitioners are rewarded for high vaccination rates. Doctors are pressured to vaccinate or face negative professional and financial consequences. Medical doctors belong to professional medical organizations which recommend vaccines.
To summarize, physicians exist in a world where vaccinations are considered the primary weapon for disease prevention. The majority come to believe in vaccine safety and effectiveness. It takes great courage, curiosity and independence for physicians to think outside of the box and do their own research on vaccines. For those who dare to think outside of the box, they can face negative professional and financial consequences.