If work hasn't been done along these applied public health lines, it could be that our policy makers see no value in developing a vaccine for a disease that no longer exists, which on the surface seems quite reasonable. Vaccines made today would still be made from the vaccinia virus, which provides a broad immunity that is effective against all known strains of smallpox. A standby facility would be ready to produce 20 million more doses each month. With that amount we could feel confident that we're covered in this country, and make the vaccine available to other countries. Perhaps it is impossible to eradicate any disease in the absolute sense.
Nobody knows how the smallpox virus originated.
There are, however, striking similarities between smallpox virus and other primate viruses, suggesting an evolutionary relationship. If the smallpox virus evolved as a human pathogen some 10,000 years ago from, say, the milder monkeypox virus, there is no reason to believe that such an evolutionary event could happen only once. The thought that someone could earnestly consider using the virus as a biological weapon deadens the spirit. If that is the case, it makes little difference whether or not we maintain our viral stores. Our future will not be determined by whether or not we keep the virus, grow the virus, mutate the virus.