Small pox eradication was not due to:

Cross-immunity with animal pox virus 203 Among the various animal pox viruses the two animal pox viruses - the monkey pox and the tanapox viruses are potentially capable of infecting humans. Small pox vaccination protects from monkey pox but not from tanapox. Monkey pox came to notice after small pox was eradicated and is a rare disease and so cross-immunity with monkey pox cannot render any contribution to small pox eradication. Rather with elimination of vaccination and waning immunity against small pox, an increase in human monkey pox cases may occur. Small pox eradication: Small pox was declared eradicated on 8th May 1980. The epidemiological factors which led to small pox eradication are as follows: Highly effective, heat stable and easily administrable vaccine that confers long-term protection. Life long immunity after recovery from the disease. Persons with sub-clinical infection did not transmit the disease. No known animal reservoir No long term carrier of the virus. Easily detectable clinical cases International cooperation