Polio and smallpox were already almost eradicated when the vaccines were introduced due to the new understanding of hygiene levels and hand washing
Utter nonsense. From the WHO:
Six common misconceptions about immunization
In Part:
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? Since sanitation is not better now than it was in 1990, it is hard to attribute the virtual disappearance of Hib disease in children in recent years in countries with routine Hib vaccination (from an estimated 20,000 cases a year to 1,419 cases in 1993, and dropping in the United States of America) to anything other than the vaccine.
Finally, we can look at the experiences of several developed countries after they allowed their immunization levels to drop. Three countries —Great Britain, Sweden and Japan — cut back the use of pertussis (whooping cough) vaccine because of fear about the vaccine. The effect was dramatic and immediate. In Great Britain, a drop in pertussis vaccination in 1974 was followed by an epidemic of more than 100,000 cases of pertussis and 36 deaths by 1978. In Japan, around the same time, a drop in vaccination rates from 70% to 20%-40% led to a jump in pertussis from 393 cases and no deaths in 1974 to 13,000 cases and 41 deaths in 1979. In Sweden, the annual incidence rate of pertussis per 100,000 children of 0-6 years of age increased from 700 cases in 1981 to 3,200 in 1985.
It seems clear from these experiences that not only would diseases not be disappearing without vaccines, but if we were to stop vaccinating, they would come back. Of more immediate interest is the major epidemics of diphtheria that occurred in the former Soviet Union in the 1990s, where low primary immunization rates for children and the lack of booster vaccinations for adults resulted in an increase from 839 cases in 1989 to nearly 50,000 cases and 1,700 deaths in 1994. There were at least 20 imported cases in Europe and two cases in U.S. citizens who had worked in the former Soviet Union.