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Mass Vaccination Not Needed to Contain Smallpox Outbreak, Researchers Say

Global Security Newswire

Conducting a mass vaccination against smallpox in the United States could save some lives in the event of an outbreak, but the risks of vaccine side effects would outweigh most benefits, researchers announced Friday (see GSN, Jan. 30).

Presenting a paper in at an American Association for the Advancement of Science conference in Seattle, Emory University researchers said that rapid detection and isolation of smallpox cases would effectively contain an outbreak, although delays of even one or two days could hamper control of an epidemic.

Although mass vaccination during or before a smallpox attack would result in fewer cases and deaths than would surveillance and containment, the researchers concluded that such a vaccination effort would cause an increased rate of vaccine-related serious illness and death that would offset the slightly lower number of smallpox illnesses and deaths.

In an earlier study the researchers concluded that targeted vaccination of the close contacts of infected individuals during a smallpox outbreak following a small attack could rival the effectiveness of mass vaccination, given a sufficiently high level of immunity within the population. Although routine smallpox vaccinations were stopped in 1972, recent studies have shown that previously vaccinated individuals retain substantial immunity.

In the current study, the Emory investigators constructed a model that simulated the spread of smallpox in a hypothetical community of typical contacts, using a population of the approximate age and household distribution of the United States, following a larger smallpox attack deliberately introduced through aerosolized virus. They found that containment and surveillance would be effective in containing a moderately large smallpox attack.

“This demonstrates the necessity for preparedness in our public health system. A rapid and efficient means of detecting cases and isolating them in case of an attack would be an essential component of the strategy of surveillance and containment,” according to Emory researcher Elizabeth Halloran (Emory University release, Feb. 14).