Current use of varicella vaccine

Live attenuated varicella vaccines, prepared with the OKA strain have been developed since the early 1970s and have been broadly studied in healthy an d immunocompromised children, adolescents and adults. They have been proven to be safe and effective in children with acute leukemia (ALL) and with ot her solid cancer in remission. Two doses given at a three month interval af ter discontinuation of immunosuppressive therapies, before and after the fi rst injection induced a seroconversion in over 90 % of the vaccinees and ga ve protection against varicella which has a severe prognosis in this popula tion, protective efficacy has also been shown against secondary tester. The varicella vaccine has also been tested on thousands of healthy children in clinical trials and on several millions of children in countries where it has been licensed and used for routine immunisation. A macule papular and s ometimes vesicular rash has been reported within three weeks after vaccinat ion in 1 to 4% of the children. Vaccine efficacy, lasting over 10 years, va ries from 65 to 100% depending on the intensity of exposure to the wild vir us and to the vaccine concentration. Nevertheless, even vaccinated children developing the disease after exposure to a wild virus always experience a mild disease, usually afebrile, with less than 50 lesions compared to aroun d 300 in non vaccinees. After more than 10 years, no increase, and even a d ecrease, in the expected incidence of tester has been reported in vaccinees . Similarly, 90% of adolescents and adults develop an immune response after two doses given three month apart with a protective efficacy of at least 7 5%. In Europe, the varicella vaccine is mostly indicated in high risk child ren with ALL whereas in other countries like the USA and Japan, universal v accination of healthy children is recommended. Such different strategies ar e linked to different perceptions of public health and the socio-economical burden of varicella, as well as on the epidemiological impact of vaccine p revention on VZV infection.