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By Dan Nixon
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. |
Bivalent
oral polio vaccine delivers powerful blow