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Varicella vaccine effective in children with HIV
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Varicella vaccine is protective in children who have HIV against both varicella and herpes zoster, according to a recently published study.
Before 1999, varicella-zoster virus was a frequent cause of illness among children living with HIV. The varicella vaccine was recommended for children with HIV on the basis of safety and immunogenicity. However, the effectiveness of the vaccine was never evaluated in these children.
A group of physicians from Columbia University College of Physicians and Surgeons, Yale University College of Medicine and St. Jude Children’s Research Hospital reviewed the medical records of children with HIV, including those receiving antiretroviral therapy between 1989 and 2007. Researchers noted varicella immunization and subsequent development of varciella or herpes zoster in 164 perinatally infected children with HIV. Typically, children with HIV are 15 times more likely to develop severe herpes zoster.
“It is critical that vaccination be given when the immunologic status is still fairly intact, before children develop AIDS,” study researcher Anne Gershon, MD, said in an interview. “That way vaccination can be predicted to be both safe and effective.”
Clinicians determined the effectiveness of the vaccine by subtracting the rate ratios for the incidence rates of varicella or herpes zoster in vaccinated children from the unvaccinated children. Researchers concluded that the vaccine was 82% effective against varicella and 100% effective against herpes zoster.
During the prevaccine era, 6% of unvaccinated children developed varicella while receiving ART and the incidence rate for varicella was 64 cases per 619 person years. By 1998, 63% of unvaccinated children that were receiving ART developed varicella and the incidence rate for varicella dropped to 19 cases per 516 person years.
Seventy-two vaccinated children developed breakthrough varicella about 4 years after their last immunization. The incidence of varicella was two cases per 296 patient years.
Clinicians noted a 63% decrease in the incidence of varicella among unvaccinated children since 1999 and also that the vaccine protected children with HIV from herpes zoster. The clinicians noted the median age of the vaccinated group was younger than the unvaccinated group.
The researchers suggested that younger children are less likely to have already had varicella and more likely to have been immunized than older children, despite evidence that the age at the time of primary infection is unrelated to the risk of herpes zoster.
Although the study consisted of an observational clinical trial and the varicella diagnosis was not laboratory verified, the children included in the study were intensively under the study conditions of the Pediatric AIDS Clinical Trials Group.
The 18-year study’s data suggest that varicella vaccine is highly effective in preventing varicella and herpes zoster in a group of perinatally HIV-infected children.
Son M. J Infect Dis. 2010;1806-1810.