The Hepatitis B virus (HBV) was led to more than double its rate of "breakout" mutations due to a universal infant vaccination campaign in China. These mutations may enable the virus to elude the vaccine, necessitating new vaccination strategies. Researchers at the Chinese Centers for Disease Control and Prevention and University of North Carolina, Chapel Hill, report their findings in an article published ahead of print in the Journal of Virology.
Until a universal vaccination program for infants was implemented in 1992, nearly ten percent of ChineseŚchildren includedŚwere infected with HBV. The vaccination campaign has protected an estimated 80 million children, dramatically reducing the percentage of children under 5 who are infected, from nearly 10 percent in 1992 to less than one percent in 2005. But these gains are in danger of being eroded as the virus develops surface mutations.
Taking advantage of 1992 and 2005 survey, investigators found that the prevalence of HBV escape mutants in children rose from 6.5 percent in 1992, before the start of the universal vaccination program, to nearly 15 percent in 2005. Among the control group of adults unaffected by the universal vaccination campaign, the rate of break-out mutants was virtually unchanged.
Researcher Tao Bian of Chapel Hill says that the vaccine remains quite effective, but that because escape mutants are likely to increase, public health officials need to track the rise of escape mutants, in order to know when it becomes time to consider new vaccination strategies. Measures that might be taken include boosting doses, adjusting the timing of vaccinations, or improving the vaccine. A next generation HBV vaccine has been invented, containing a second antigen in addition to the virus' surface antigen. That means that both antigens would have to develop breakout mutations in order to elude the vaccine.