Bivalent oral polio vaccine delivers powerful blow
A health worker in Nigeria marks a girl’s pinkie finger to indicate immunization against polio. Use of the bivalent oral polio vaccine has helped slash incidence of the disease there by 98 percent. Photo by Joseph Lorenzo
The bivalent oral polio vaccine (bOPV) is proving to be a potent weapon in the global battle to eradicate the disease.
Developed to stop transmission of the type 1 and type 3 wild polioviruses simultaneously, bOPV was introduced in all four polio-endemic countries -- Afghanistan, India, Nigeria, and Pakistan -- in late 2009 and early 2010. It has helped reduce the incidence of polio in India to 39 cases as of 26 October, compared to 498 for the same period in 2009. The number of cases in Nigeria has fallen to 8 from 382 for that period.
"There’s been the largest ever year-to-year drop in polio cases following the use of bOPV," says Dr. Bruce Aylward, director of the Global Polio Eradication Initiative (GPEI) at the World Health Organization.
The results of a field trial published in the British medical journal the Lancet in October underscore the effectiveness of the new vaccine. The randomized, double-blind, controlled trial, conducted by WHO between August and December 2008, involved 830 newborns in India who received bOPV or another polio vaccine.
"In this study we showed that the bivalent [vaccine] is much better than the trivalent," says Dr. Roland Sutter, coordinator of the GPEI’s research and product development team. "We get about 30 [percent] to 40 percent more immunity [from] the bivalent compared to the trivalent for types 1 and 3." The study also showed that bOPV is just about as good as the monovalent vaccines, which protect against only one strain of polio.
"The big story is not the study itself but the impact the vaccine has already had on transmission [of the wild poliovirus] in India and Nigeria," Sutter says. "In both countries, other factors such as improved program performance also played a critical role."
Rotary International has been a major player in bringing about that achievement, Aylward said at the meeting of the International PolioPlus Committee in October. PolioPlus grants awarded by The Rotary Foundation "have been strategically linked closely to all of the major gains that we’ve seen over the last 12 months," he noted. "The most striking impact is what your funds have achieved in Nigeria. Over $23 million has gone into operational costs. That 98 percent drop in cases could not have been achieved without that money to get the vaccine to the kids."
Health officials see an expanded role for bOPV in the vaccine arsenal. On 26 October, 15 African countries launched a synchronized mass immunization campaign, the third on the continent in 2010. About 290,000 vaccinators went door to door to immunize 72 million children -- 55.7 million of them received bOPV.
By simplifying the logistics of immunizing children against polio, bOPV has become the centerpiece of the global strategy to end the disease.
"This vaccine could get us over the top and to the finish line for eradication," Sutter says.
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