Brief Report: Conclusions and Recommendations of the Advisory Committee on Poliomyelitis Eradication --- Geneva, Switzerland, October 2005

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The second meeting of the Advisory Committee on Poliomyelitis Eradication (ACPE) was convened in Geneva, Switzerland, on October 11--12, 2005, to provide the World Health Organization (WHO) and the Global Polio Eradication Initiative with advice on program policies for 1) interrupting wild poliovirus (WPV) transmission worldwide, 2) limiting the international spread of circulating polioviruses, and 3) refining the program of work for eventual cessation of immunization with oral poliovirus vaccine (OPV). This report summarizes the results of that meeting.*

Interrupting WPV Transmission

As of October 25, 2005, paralytic polio cases attributed to WPV had been reported from 16 countries, including five of the six countries that were endemic for indigenous WPV during 2004 (Table). In the disease-endemic reservoirs in India and Pakistan, transmission had been reduced by 50%, compared with the same period in 2004.

The development, licensure, and use of monovalent OPV type 1 (mOPV1) appears to have had a substantial impact on WPV circulation in polio-endemic countries. Afghanistan, Egypt, India, and Pakistan have implemented supplementary immunization activities (SIAs) using mOPV1, and Afghanistan and India might implement rounds in selected areas using monovalent OPV type 3 (mOPV3) within the first 6 months of 2006, depending upon the evolving epidemiology of types 1 and 3. Preliminary evidence suggests a positive impact of mOPV1 in restricting WPV transmission, compared with use of trivalent OPV (tOPV). ACPE recommends that 1) mOPV1 be used in polio-endemic countries with circulation of WPV type 1 only and 2) SIA vaccine strategies include mOPVs in countries where two poliovirus serotypes circulate (types 1 and 3).

For Nigeria, ACPE recommends that highest priority be placed on increasing the quality and number of routine and SIA activities in the polio-infected states and that consideration be given to introduction of mOPV1 as early as possible to complement the ongoing work to improve SIA quality. In polio-free countries bordering polio-endemic areas, mOPV should be considered for use in SIAs on a case-by-case basis. In all countries, tOPV or IPV should continue to be used in routine vaccination activities, as guided by national immunization policy.

Limiting the International Spread of Circulating Polioviruses

The impact of outbreaks attributed to importations of WPVs in polio-free areas has increased substantially in 2004 and 2005. Approximately 60% of all cases reported globally in 2005 have been from outbreaks in previously polio-free countries. Poliovirus transmission in the areas of West and Central Africa that were reinfected in 2003 and 2004 is now stopping, and Sudan has not reported any cases since June 2005. However, more recent outbreaks in Angola, Eritrea, Ethiopia, Indonesia, Somalia, and Yemen are of considerable concern.

ACPE recognizes the significance of large-scale outbreaks associated with imported polioviruses in areas of suboptimal population immunity and the risks these viruses pose to surrounding communities. Therefore, ACPE recommends that the Director-General of WHO consider declaring the following scenarios as public health emergencies of international concern (i.e., constituting a public health risk to other countries through international spread of disease, potentially requiring a coordinated international response): 1) detection of a circulating poliovirus in any previously polio-free geographic area that does not have survey-confirmed routine childhood polio vaccination coverage of >90% and has not conducted polio SIAs within the preceding 6--12 months, or 2) any poliovirus outbreak that continues to expand geographically for more than 60 days after confirmation of the index case.

Polio-free countries detecting circulating poliovirus should immediately implement ACPE's Standing Recommendations for Responding to Circulating Polioviruses in Polio-Free Areas, particularly completion of an expert risk assessment and large-scale response plan, immediate initiation of an in-depth epidemiologic investigation, and implementation of local control measures according to national guidelines (1). Moreover, in accordance with the standing recommendations, countries should plan to continue large-scale mOPV polio campaigns until at least two full rounds have been conducted after the most recent virus is detected. The need for further activities will depend on the epidemiology of the outbreak and risk for further importation.

In view of emerging evidence demonstrating the capacity of some vaccine-derived polioviruses (VDPVs) to circulate and cause outbreaks of paralytic poliomyelitis, ACPE recommends that the case definition for poliomyelitis within the WHO International Health Regulations be updated to include circulating VDPVs (2).

Refining the Program of Work for Cessation of the Use of OPV

ACPE reaffirms the guidance outlined in the 2003 WHO position paper (3) on the use of inactivated poliovirus vaccine (IPV) in OPV-using countries. The paper recommended against adoption of IPV alone or in a sequential schedule in tropical developing countries, where OPV might be more effective. A proposed supplement is currently under development, with a focus on preparations for vaccination policy decisions for the OPV-cessation era. WHO should continue investigating the potential use of newer products in the post-OPV era, including fractional doses of IPV and Sabin-strain IPV. Because assumptions regarding VDPVs underpin the strategy for OPV cessation and understanding of VDPVs continues to evolve, highest priority should be given to better characterization of the incidence and behavior of these viruses, particularly in areas of low population immunity.

Reported by: Polio Eradication Initiative/Office of the Director-General and Dept of Immunization, Vaccines and Biologicals, World Health Organization, Geneva, Switzerland. United Nations Children's Fund, New York, New York. Rotary International, Evanston, Illinois. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Global Immunization Div, National Immunization Program, CDC.

References

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