Smallpox case study

People previously vaccinated for smallpox can develop a febrile illness after exposure to a smallpox case. Typically, fever begins suddenly, reaches 39°C and is associated with headache and occasionally backache. Symptoms resolve within 48h. Serologic studies in these patients have suggested the diagnosis of variola sine eruptione by demonstrating a significant rise in variola antibody titers following the illness (25). 

Serologic studies have also shown that recently vaccinated contacts of smallpox cases can develop an actual subclinical case, without any symptoms. Persons with subclinical infection have not transmitted the infection to their contacts (25). 

Smallpox vaccination is also effective if given after exposure to the disease. Studies of household contacts in India and Pakistan revealed that postexposure vaccination reduced secondary cases up to 91%. The lowest secondary attack rates occurred in contacts vaccinated less than seven days after exposure. Smallpox cases that occurred were typically less severe (modified smallpox) in household contacts receiving postexposure vaccination (25). 

In studies conducted during the smallpox eradication program and by surveillance for cases in newly smallpox-free areas it was reasoned that if the virus were... 

The susceptibility of people who received the vaccine 29 or more years ago is uncertain, because clinical studies have never measured the duration of immunity following vaccination. Given the likely susceptibility of the current US population, with most people not vaccinated or vaccinated remotely, a smallpox attack would likely affect adults as well as children (26). Because of the high case fatality rate, physicians suspecting a single case must treat it as an international health emergency and immediately contact local and state public health authorities. 

Controlled studies evaluating smallpox vaccine effectiveness are not available. However, studies of exposed household case contacts demonstrated a 91-97% reduction in cases among household contacts with vaccination scars compared to contacts without scars. None of these studies investigated the association between attack rates and time since vaccination or potency of the vaccine, so they may underestimate current levels of protection in the United States (15). 

During the waning years of routine smallpox vaccination, in 1968, studies estimated the rate of inadvertent inoculation at 529 cases per million primary vaccinations. More recently, from January 24, 2003 to December 31, 2003, 39,213 civilian... 

A recent program to protect healthcare workers from a possible bioterrorist attack with smallpox reported cases of myocarditis and pericarditis following vaccination (MMWR, 2003), and other studies provided evidence that these effects might be associated causally with vaccinia vaccination (Feery, 1977 Halsell et al., 2003) and may have caused the death of one vaccine recipient (Finlay-Jones, 1964). 

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