Smallpox modified

Modified smallpox occurs typically in previously vaccinated people. The prodrome is less severe than in ordinary smallpox and patients are usually afebrile during development of the rash. Skin lesions, generally fewer in number, evolve more quickly, and are more superficial and lack uniformity compared to ordinary smallpox. Modified smallpox is rarely fatal, and is easily confused with chickenpox. 

The Variola major rash presents in four distinct ways, ordinary, modified, flat, and hemorrhagic. The type of rash presentation is probably associated with the strength of the immune response. Ordinary smallpox is most frequent, whereas the mild modified form, seen primarily in previously vaccinated patients, is uncommon. The most severe presentations, flat and hemorrhagic, are usually fatal but are fortunately rare. Smallpox infection can also occur without a rash. A mild but uncommon variation of variola infection, variola sine eruptione (meaning smallpox without a rash) occurs generally in previously vaccinated people and involves a febrile illness alone. Asymptomatic infections are also possible, yet rare. 

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). 

D. Vaccine/Prophylaxis. Smallpox vaccine (vaccinia virus) is a licensed live poxvirus vaccine that induces strong cross-protection against smallpox. Reliable data are sparse as to efficacy and durability of protection. The duration vaccinia induced immunity is at least 3 years. Vaccine immunity may prevent or modify illness. Fully immune individuals exposed to the virus by the respiratory route may develop fever, sore throat, and conjunctivitis ("contact fever") lasting several days. The vaccine is administered by dermal scarification or intradermal jet injection. The appearance of a vesicle or pustule within several days indicates that the vaccine will be effective. Other available countermeasures include the postexposure use of Vaccinia immune globulin or primary vaccination within 3-4 days of exposure yields some protection. 

Boseley S, Borger J (2005). US Scientists Push for Go-Ahead to Genetically Modify Smallpox Virus. The Guardian, May 16. 

Smallpox virus vector MVA (Modified Vaccinia Ancara) No... 

Poxvirus vectors encompass vaccinia derived from the smallpox vaccine and more attenuated variants like ALVAC or MVA (Modified Vaccinia Ankara). Their genome consists of single-stranded DNA of 130 to 300 kb pairs. Replication is restricted to the cytoplasm of cells and high amounts of protein are synthesized by the cell following transduction. Most applications therefore involve intramuscular vaccination. 

Partial immunity from vaccination resulted in modified-type smallpox, in which sparse skin lesions evolved variably, often without pustules, and quickly, with crusting occurring as early as the seventh day of illness. Some fully immune individuals... 

There are two clinical forms of smallpox. Variola major is the severe and most common form of smallpox, with a more extensive rash and higher fever. There are four types of variola major smallpox ordinary (the most frequent type, accounting for 90% or more of cases) modified (mild and occurring in previously vaccinated persons) flat and hemorrhagic (both rare and very severe). Historically, variola major has an overall fatality rate of about 30% however, flat and hemorrhagic smallpox usually are fatal. Variola minor is a less common presentation of smallpox, and a much less severe disease, with death rates historically of 1 % or le.ss. 

Vaccination within 3 days of exposure will prevent or significantly lessen tlie severity of smallpox symptoms in the vast majority of people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may modify the severity of disease. 

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