The World Health Organization's strategy for eradicating polio will remove serotype 2 poliovirus from the oral polio vaccine (OPV) because this component causes many of the few new cases, according to a new clinical report.
Walter A. Orenstein, MD, professor and associate director of the Emory Vaccine Center, Atlanta, Georgia, and a former member of the American Academy of Pediatrics Committee on Infectious Diseases, and colleagues describe the strategy in an article published online December 29 in Pediatrics.
OPV consists of three serotypes of attenuated virus. Wild serotype 2 was last detected more than a decade ago, and wild serotype 3 has not been seen since 2012. Circulating vaccine-derived polioviruses that arise from mutation of the attenuated viruses account for more cases than does natural infection. Therefore, eradication requires that this route of transmission stop.
The World Health Organization's Endgame and Strategic Plan will, in a stepwise fashion, remove serotype 2 poliovirus from the OPV. The serotype is responsible for 40% of cases of vaccine-associated paralytic polio and for 98% of circulating vaccine-derived polioviruses detected since 2012. In addition, serotype 2 inhibits immunity to serotypes 1 and 3.
Before conversion to bivalent OPV, at least one dose of trivalent inactivated polio vaccine (IPV) will be used, by 2015, in the more than 120 countries currently using OPV as "insurance" to protect against serotype 2 when it is eliminated from OPV. Eliminating serotype 2 in OPV will begin in 2016.
The goal is for the switch of OPV to a bivalent formula to halt all polio by 2018, after which use of the OPV will be stopped altogether.
"Eliminating polio in the remaining endemic countries will ease burdens and free up resources for these countries to focus on other areas of development, both health-related and other areas," the authors write. "Because routine use of IPV is expected to boost immunity to poliovirus types 1 and 3, if IPV is incorporated into the routine immunization programs in these endemic countries soon, it could hasten eradication of those types."
The report lists obstacles to implementing the switch to bivalent OPV. These include the cost and more complex delivery (by injection) of IPV, cold-storage costs, and the inferior intestinal immunity that IPV confers. Most industrialized nations use IPV; most developing countries use OPV, because of the ease of administration, the report states.
The Scientific Declaration on Polio Eradication, which experts from 80 nations signed in 2013, endorses this plan and emphasizes the danger of seeking control rather than eradication: "[W]e could expect up to 200 000 cases annually within a decade if the polio eradication effort is stopped, effectively reversing progress made over the past 25 years," the researchers write.
"Until eradication is achieved, we will always be at risk for poliovirus reappearing anywhere in the world."
The American Academy of Pediatrics provides the following action points for pediatricians:
educate parents and patients about the importance of global polio eradication;
vaccinate patients, including booster IPV for international travelers and healthcare workers or researchers exposed to poliovirus;
alert health authorities about children presenting with polio symptoms; and
become an active advocate for global immunization against polio.
Dr Orenstein receives funding from the Bill and Melinda Gates Foundation. The other authors have disclosed no relevant financial relationships.
Pediatrics. Published online December 29, 2014. Full text
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Cite this: Endgame for Polio Eradication - Medscape - Dec 29, 2014.