Booster Shots May Reduce Chickenpox Rates

An outbreak of chickenpox among highly vaccinated schoolchildren indicates that waning immunity over five years may leave children vulnerable, public health officials report. The findings suggest that booster chickenpox vaccinations may be warranted. As reported in the medical journal Pediatrics, Dr. Paul R. Cieslak and associates describe a chickenpox outbreak that occurred at an Oregon elementary school in 2001, even though nearly all of the students had been vaccinated. To determine vaccine effectiveness and risk factors associated with breakthrough disease, the researchers analyzed outcomes for 414 students in the 16 classrooms involved. The outbreak included 21 cases. Among 218 students with no prior history of chickenpox, 211 (97 percent) had been vaccinated. Seven students were considered susceptible, based on no history of chickenpox or of immunization. The first three cases occurred in susceptible students, while the remaining 18 cases occurred in vaccinated individuals. Attack rates were 12 percent among vaccinated students and 43 percent among susceptible students. The authors estimate that vaccine effectiveness was 72 percent. Cases occurred in 23 percent of 65 individuals vaccinated more than five years before the outbreak, and in three percent of those vaccinated less than five years before. Booster chickenpox shots deserve “additional consideration” to decrease the rates of vaccine failure, Cieslak’s group suggests. However, the efficacy and cost-benefit of this strategy is as yet unknown. But even though outbreaks of chickenpox can occur in vaccinated children, the extent and severity of illness is probably decreased. So “the routine use of (chickenpox) vaccine should still be encouraged,” they maintain. (SOURCE: Reuters Health, Pediatrics, March 2004)

Posted On: 3 March, 2004

Modified On: 5 December, 2013