Effectiveness
Scientific evidence for the effectiveness of large-scale vaccination campaigns is well-established. Vaccination campaigns helped eradicate smallpox, which once killed as many as one in seven children in Europe, and has nearly eradicated polio. As a more modest example, infections caused by Haemophilus influenzae, a major cause of bacterial meningitis and other serious diseases in children, have decreased by over 99% in the US since the introduction of a vaccine in 1988. Full vaccination, from birth to adolescence, of all US children born in a given year saves an estimated 33,000 lives and prevents an estimated 14 million infections.
Some opponents of vaccination argue that these reductions in infectious disease are a result of improved sanitation and hygiene (rather than vaccination), or that these diseases were already in decline before the introduction of specific vaccines. These claims are not supported by scientific data; the incidence of vaccine-preventable diseases tended to fluctuate over time until the introduction of specific vaccines, at which point the incidence dropped to near zero. A Centers for Disease Control website aimed at countering common misconceptions about vaccines argued: "Are we expected to believe that better sanitation caused incidence of each disease to drop, just at the time a vaccine for that disease was introduced?"
Other critics argue that immunity given by vaccines is only temporary and requires boosters, whereas those who survive the disease become permanently immune. As discussed below, the philosophies of some alternative medicine practitioners are incompatible with the idea that vaccines are effective.
Read more about this topic: Vaccine Controversies