First Polio Vaccine Combo Campaign Nets Almost 100% Coverage

Larry Hand

March 20, 2014

Combined administration of inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV) in a mass campaign can achieve more than 90% coverage, according to an article published in the March 21 issue of the Morbidity and Mortality Weekly Report. However, combined campaigns cost more than OPV-only campaigns, and particular emphasis needs to be placed on training and supervising vaccinators.

Mohamed A. Sheikh, MD, from the Ministry of Health, Kenya, and colleagues describe the first-ever polio vaccine combination campaign. , Kenya conducted the campaign in December 2013 near its border with Somalia. Earlier last year, 217 cases of polio caused by wild polio virus type 1 (WPV1) of Nigerian origin had been reported in the Horn of Africa area, with 194 cases in Somalia, 14 in Kenya, and 9 in Ethiopia.

A total of 299 vaccinator teams fanned out to vaccination sites in 173 refugee camps and 126 surrounding communities, and mobile teams traveled to scattered nomad settlements. Each team consisted of a healthcare worker who administered IPV shots and either 2 or 3 volunteers who administered the oral OPV. One of the volunteers went door to door urging caregivers to take their children to the vaccination sites.

The teams targeted 126,000 children aged 59 months or younger. Those younger than 6 weeks received only OPV, but children aged 6 weeks to 59 months received OPV immediately followed by IPV. Volunteers either kept tallies or marked the fingers of children who had been vaccinated.

The authors report that in focus group discussions before the campaign, the participants voiced confidence in IPV injections, which provide protection in the bloodstream, and in oral OPV, which provides protection in the gut.

Trained campaign monitors assessed the activities of 47 randomly selected teams. Of those, 43 (91%) had sufficient staff, vaccine, and supplies for the mission. Five teams (11%) made an error in IPV administration in either dosing or injection site, 2 teams (4%) prefilled syringes, and 8 (17%) recapped needles during injection preparation. Two teams (4%) made errors in finger marking, and 7 (15%) erred in tallying.

Variations occurred among teams in the way they handled vaccines. One team had frozen IPV vials, and other vaccines were exposed to temperatures that were either higher or lower than recommended.

The authors estimate that the total cost per child vaccinated came to $3.27 for IPV and $0.50 for OPV, including cost per dose ($2.09 for IPV and $0.14 for OPV).

Using cluster survey methodology during the 5 days after the campaign, researchers surveyed 1286 houses, finding that caregiver recall information on IPV or OPV receipt was available for 2161 children in 1016 households. They calculated coverage at 92.8% in refugee camps and 95.8% in surrounding communities. They found that 40 (34%) of 118 eligible children in 65 nomadic households had received the combination vaccine.

Lessons for Future Campaigns

"Challenges in field implementation of the IPV/OPV campaign can provide lessons for future campaigns," the authors write. "Comprehensive precampaign planning of cold chain requirements, consideration of vaccine vial monitor inclusion on IPV vials, and appropriate staff training on existing guide¬lines for prevention of vaccine damage from heat or freezing will be important to prevent loss of vaccine effectiveness in future campaigns," they add.

According to the Polio Eradication and Endgame Strategic Plan 2013-2018, OPV is intended to be discontinued after WPV1 is eradicated, and IPV is intended to be introduced by the end of 2015 in 126 countries now using only OPV, the authors write.

They conclude, "The Kenya experience has shown that IPV also can be provided in campaigns with high coverage and community acceptance, although at a higher cost than OPV-only campaigns and requiring particular attention to training and supervision."

Worldwide Update

In an accompanying article published in the same issue of the Morbidity and Mortality Weekly Report, Ousmane M. Diop, PhD, from the Department of Immunization, Vaccines, and Biologicals, World Health Organization, Geneva, Switzerland, and colleagues report on vaccine-derived polioviruses (VDPVs) detected worldwide between July 2012 and December 2013, as well as continuing outbreaks. VDPVs can emerge in areas with low OPV coverage.

Outbreaks continue in countries "where conflict and insecurity [have] limited access of immunization teams to children," the researchers write.

Recent outbreaks occurred, including 1 in Pakistan in 2012 and 1 in Chad, which spread to Cameroon, Niger, and northeastern Nigeria. An earlier outbreak in Afghanistan continued into 2013, and an earlier outbreak in Somalia continued and spread to Kenya in 2013.

The researchers also report that the number of countries with circulating VDPVs increased from 6 to 7 since an April 2011 to June 2012 report, including the above-mentioned countries and China. Other outbreaks in other countries "appeared to have been interrupted," they write.

The World Health Organization has a plan to replace worldwide trivalent OPV with bivalent OPV by 2016 after introduction of at least 1 dose of IPV containing the 3 serotypes of poliovirus (PV1, PV2, and PV3). Because WPV2 was eradicated in 1999, PV2 polio cases have resulted from use of trivalent OPV, the researchers write. The Polio Eradication initiative has incorporated the OPV switch in its plan.

The OPV switch "will prevent virtually all" new outbreaks and infections, the researchers write. However, some persons with chronic infections may continue to secrete poliovirus for at least a decade after the last OPV dose, they add, and "maintenance of high levels of population immunity by comprehensive coverage with IPV will be essential."

Morb Mortal Wkly Rep. 2014;63:237-248. Sheikh full text, Diop full text


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