Efforts on track to eradicate world of polio by 2018
- Copyright © 2013, The American Academy of Pediatrics
We are on the verge of permanently ridding the world of polio, a disease synonymous with paralysis and death.
Since the last U.S. outbreak of polio caused by indigenous transmission of polioviruses in 1979, efforts have shifted to wipe out the disease in the rest of the world. In 1988, a World Health Assembly Resolution called for global eradication of polio by 2000. Thirteen years after the target year, polio still is circulating in a handful of countries. Only Pakistan, Nigeria and Afghanistan are considered to be endemic for polio compared to 125 countries in 1988. Further, worldwide efforts have resulted in the lowest number of polio cases ever recorded — 223 cases in 2012 compared to about 350,000 in 1988.
Of the three wild virus (naturally occurring) serotypes of polio, wild type 2 appears to have been eradicated, and wild type 3 virus is on the verge of being eradicated. We are better poised now than ever before to eradicate polio caused by wild virus. The live oral poliovirus vaccine (OPV) will remain the major tool to eradicate wild polioviruses in the world until that goal is achieved.
In 127 countries, OPV is used instead of inactivated poliovirus vaccine (IPV) due to several factors:
It costs less than IPV (15-20 cents per dose of OPV vs. more than $2 per dose for IPV, www.unicef.org/supply/files/IPV_Supply_Status_UNICEF-SD_v6.pdf).
It induces superior intestinal immunity compared to IPV.
The vaccine virus can be shed, leading to passive immunization of unvaccinated persons.
It comes in oral drops, which are easier to administer than injections.
Despite the benefits, in rare cases, OPV can cause vaccine-associated paralytic paralysis (VAPP) in vaccine recipients or their close contacts. The live vaccine virus also can acquire mutations that confer the transmissibility and neurovirulence properties of wild viruses, leading to polio outbreaks caused by these altered viruses known as circulating vaccine-derived polioviruses (cVDPVs). In fact, due to progress in eradication, for the first time ever, vaccine viruses may have caused more cases of polio globally than wild viruses in 2012.
Therefore, to eradicate all polio, use of OPV eventually will have to be stopped. However, if polio eradication efforts stop prior to achieving eradication, a major resurgence of wild virus polio is predicted. Within a decade, at least 200,000 cases of paralytic polio would be expected worldwide every year.
To address this problem, the Global Polio Eradication Initiative has developed a strategic plan to wipe out all polio disease by 2018. The initiative is led by the World Health Organization (WHO), UNICEF, Rotary International, and the Centers for Disease Control and Prevention. Many other organizations are involved, and technical and policy oversight is provided by the WHO’s Strategic Advisory Group of Experts on Immunization. The strategic plan has four major objectives:
Detect and interrupt all poliovirus transmission.
Strengthen immunization systems (to facilitate introduction of affordable IPV) and withdraw OPV use.
Contain poliovirus and certify interruption of transmission.
Develop a legacy plan to secure a polio-free world and build on the experience and assets to address other health priorities.
Type 2 vaccine-derived polioviruses account for more than 95% of all cVDPV outbreaks detected in recent years and approximately 40% of VAPP cases. Therefore, a critical intermediate step to meet objectives one and two is to replace the trivalent OPV, which protects against types 1, 2 and 3, with a bivalent OPV, which protects only against types 1 and 3.
The plan also calls for introducing at least one dose of affordable IPV in routine immunization programs by 2015 prior to switching to bivalent OPV in 2016. This is necessary to provide a type 2 immunity base against the possible emergence of type 2 cVDPVs during or immediately after the switch and potential breaks in containment of type 2 wild virus stocks in laboratories or vaccine manufacturing sites. Although naturally occurring type 2 wild virus has not been detected since 1999, many infants and young children would be susceptible to wild type 2 poliovirus and cVDPVs if it is re-introduced accidentally or intentionally if they received only bivalent OPV and no IPV.
Under the new plan, wild poliovirus interruption is targeted by the end of 2014. Routine vaccination with bivalent OPV would continue until 2018. At that point, if no wild viruses have been detected for at least three years, eradication could be certified and all routine use of OPV stopped shortly thereafter. Continued IPV use in routine immunization programs globally would be strongly recommended for at least five years after certification, and potentially longer depending on the evolution and management of post-eradication risks.
Use of IPV faces major obstacles, including more costly administration via needle and syringe and cold-chain storage requirements. Nevertheless, the benefits of IPV in ensuring eradication more than outweigh these costs. Cost savings of a polio-free world would be garnered by eliminating the need to treat polio-stricken patients, as well as potentially eliminating the need for all polio vaccines, as with smallpox.
U.S. pediatricians can help in several ways to ensure that the U.S. legacy of eradicating polio is sustained and enjoyed by all countries. First, you can educate parents and patients about this important achievement in public health and advocate for vaccines recommended in the United States, including those against polio. In addition, ensure that patients who are traveling internationally receive all recommended vaccines, including IPV when appropriate. Furthermore, advocate with government officials about the importance of funding and technical assistance for global immunization programs, especially the Global Polio Eradication Initiative.
You also can advocate with pediatric societies in developing and middle-income countries to support incorporation of at least one dose of IPV to complement OPV used in routine immunization programs. Lastly, you can help make polio eradication a reality by working with local Rotary Clubs or volunteering with the United Nations Volunteers Program.
More information about the Global Polio Eradication Initiative and the Eradication Endgame and Strategic Plan can be found at http://www.polioeradication.org/Resourcelibrary/Strategyandwork.aspx
To learn which vaccines are recommended for international travelers, visit http://wwwnc.cdc.gov/travel.
For more resources, visit the AAP Global Immunization website.
For information on the United Nations Volunteers Program, visit http://www.unv.org/how-to-volunteer.html.
Dr. Orenstein is a member of the AAP Committee on Infectious Diseases. Katy Seib, M.S.P.H., research project manager at Emory University, contributed to this article.