After the eradication of smallpox, manufacturing of smallpox vaccine virtually ceased since there was no commercial incentive for production. However in the 1990s, amid concerns about the use of smallpox as a biological weapon, the US government announced a stockpiling programme. At that point there were only 15 million doses of smallpox vaccine available in the US , and these doses had been manufactured 20 or more years earlier.
The rationale for development of new smallpox vaccines is that they are based on first-generation vaccines that were proven to be effective against smallpox. The vaccines contain the vaccinia virus - a relative of the smallpox virus - but they cannot cause smallpox. At present, the new second-generation smallpox vaccines are investigational and only available for emergency stockpiling. Clinical trials are continuing and, once the clinical programmes are completed, applications will be made for licensure.
Research is continuing to develop safer vaccines that are also effective against the disease. In years to come, it is likely that there will be a range of vaccines and treatments, providing a repertoire of defences against smallpox.
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