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ASSESSING AND MITIGATING THE RISK OF OUTBREAKS OF WILD POLIOVIRUS IN POLIO FREE AFRICAN COUNTRIES

Sunday, 31st of August 2014

ASSESSING AND MITIGATING THE RISK OF OUTBREAKS OF WILD POLIOVIRUS IN POLIO FREE AFRICAN COUNTRIES

Although Africa has only one endemic country remaining, the continent has in the past seen WPV importations from outside and inside the region (India to Angola, when India was still endemic; Nigeria to the Horn of Africa in 2013). Moreover, fragile states (C.A.R. and Somalia) are a continuing risk, as are the five countries in which Ebola control measures place a strain on overstretched health systems.

Excerpt below; full text is at http://www.who.int/wer/2014/wer8935.pdf?ua=1

 

DISCUSSION

African countries continue to be at risk for outbreaks due to WPV, as evidenced by the 2 multi-country outbreaks during 2013–2014. Low immunity levels of children caused by chronic weaknesses in the delivery of immunization services puts countries at risk for continued spread of WPV after importation of the virus.

Although insecurity is a key factor in preventing access to children for the purpose of vaccination in Africa, including the complex humanitarian emergencies in Central African Republic, South Sudan, and Somalia, insecurity was not a factor in preventing and/or mitigating the size of the outbreak in Cameroon and Equatorial Guinea.

GPEI partners recently formalized the way that risk assessments are conducted to better inform the planning of the international polio SIA calendar and provision of technical assistance. The current GPEI process for assessing risks in polio-affected WHO regions uses a consensus of the different approaches followed by CDC, WHO, and the Institute for Disease Modeling to evaluate the polio vaccination dose history of children with NPAFP and other factors. The review of country risk profiles in May 2014 was used by the GPEI partnership to plan the vaccination schedule for the second half of 2014, substantially increasing the number of planned campaigns in polio-free countries and in planning focused technical assistance to enhance SIA effectiveness.

The simple empiric approach presented here has essentially the same outcome as the formal process in assessing susceptible children and is similar to the risk assessments conducted by WHO Regional Offices.

SIAs, by delivering large numbers of vaccinations in a short period, are the most effective way of  polio-free countries might not be sufficiently planned or well-supervised, and the campaigns suffer in quality. Also, in the recent African outbreaks, the quality of many of the initial response SIAs was noted to be poor, because of inadequate planning, supervision and coordination.

One way to improve SIA performance is through coordination workshops for Ministry of Health staff, community leaders, and local partners, to develop and use detailed local micro plans in order to identify repeatedly missed subpopulations and develop effective logistical means, training, and supervision.

The data used for risk assessments have limitations. National coverage estimates are subject to overestimation; annual NPAFP data for smaller countries can fluctuate significantly; recall histories may be inaccurate; and surveillance may be limited or biased by imprecise population estimates. However, even with such limitations, the data are highly informative.

In a coordinated international effort to reduce international exportation of WPV the Director-General of WHO declared the recent international spread of WPV a public health emergency of international concern and issued temporary recommendations under the International Health Regulations (IHR 2005): (i) ensuring that residents and long-term visitors, including adults, traveling from Cameroon, Equatorial Guinea, Pakistan, and Syria receive polio vaccination before international travel, (ii) encouraging residents and long-term visitors, including adults, traveling from Afghanistan, Ethiopia, Iraq, Israel, Somalia, and Nigeria to receive polio vaccination before international travel and (iii) ensuring that such travellers from exporting countries are provided with an International Certificate of Vaccination documenting vaccination status. These recommendations were recently extended.

The success of polio eradication efforts in Africa has led to a decrease in the number of countries with confirmed poliomyelitis cases – from 20 in 2009 to 3 in 2012. In 2013, that number increased to 6 with >80% of the cases found outside Nigeria, the one endemic country on the continent. The events of the past 18 months show that all countries on the continent remain at risk for WPV outbreaks as long as circulation of the virus continues. To stop current outbreaks, prevent additional spread, and interrupt indigenous transmission in Nigeria, concerted efforts are needed to raise childhood immunity in the second half of 2014 and take the opportunity to interrupt all WPV transmission in Africa.

Going forward, governments at the national and subnational levels will need to remain committed, implement immunization activities as needed, and undertake other preparedness measures to lower the risk of infection in order to achieve eradication.