disease information
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Varicella (chickenpox) |
Chickenpox (varicella) is a highly contagious viral disease with humans being the only source of infection.
Person-to-person transmission occurs primarily through direct contact with respiratory tract secretions of infected individuals and is transmitted occasionally via airborne route. The incubation period of varicella is 14-16 days with a range from 10 to 21 days. Chickenpox is infectious 1-2 days before to 4-5 days after the onset of the rash or until all the lesions have crusted over. Mandatory vaccination for varicella started in Maine as of 2003 and is now a requirement for school admission.
There were 366 cases of chickenpox reported in 2007 compared with 222 in 2006.
In 2006, ACIP recommended that a second dose of varicella vaccine be administered to all children, with the first dose administered at 12-15 months and a second dose administered at 4-6 years. A two-dose series was also recommended for those not previously vaccinated.
Varicella vaccine is a live attenuated viral vaccine. Studies place the effectiveness of one dose of the varicella vaccine above 70%. A two-dose series is estimated to be more than 90% effective in preventing infection. Breakthrough infection has been reported in vaccinated individuals.
Source: Reportable Infectious Diseases in Maine: 2007 Summary
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Varicella
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