Curbing an Outbreak of Circulating Vaccine Derived Poliovirus Type 2 in Dollo Zone, Somali Region, Ethiopia: Response to Outbreak

"In this scenario,...resource mobilization, advocacy, and social mobilization may be the reason for the high vaccination coverage among children under five years in remote, challenging, and hard-to-reach areas..."

In under-immunised communities, the live, weakened virus originally contained in oral polio vaccine (OPV) can genetically revert into a form that can cause paralysis if allowed to circulate: circulating vaccine-derived poliovirus (cVDPV). Conducted in Bokh woreda, Dollo Zone, Somali Region, Ethiopia, this study describes the response to a cVPDV type 2 outbreak declared on June 9 2019 in Dollo Zone, Somali Region, Ethiopia. Lessons could be learned about how responders addressed difficulties in coordinating teamwork, communication, and stakeholders' engagement in a pastoralist setting.

The index child for the outbreak was a 39-month-old female living in Angalo kebele of Bokh woreda, Dollo Zone, who had the onset of flaccid paralysis on May 19 2019. Three children in direct contact with the index case had stool samples positive for poliovirus type 2, leading to the outbreak declaration. After verifying that the cases were caused by the polio-vaccine-initiated virus, a team was established to respond. The team prompted a rapid response (RR) from June 22-25 2019 by vaccinating all under 5-year children in the Dollo Zone with a monovalent oral poliovirus-2 (mOPV2) where cases of cVDPV2 were found. Moreover, the team expanded the mOPV2 supplementary immunisation activities (SIA-1 and SIA2) to adjacent zones and continued vaccinating all under-5 children, more than a month apart.

One element of the team's work was community mobilisation, advocacy, and social mobilisation related to the investigation and response. For example, they encouraged parents to vaccinate their children through Jummah prayer at the mosques, use of megaphones, and house-to-house mobilisation by trained community volunteers. The latter strategy was the preferred one to achieve the objective of reaching all children. In addition, the team visited Quran schools, kindergartens, hospitals, health centres, water points, streets, markets, and border crossing points to maximise the chance to raise awareness about the need to immunise more children - and to actually provide the OPV drops. The team coordinated zonal and woreda command post meetings, where problems encountered during the campaign were discussed and corrective actions undertaken based on the issues identified.

Furthermore, the CORE Group Polio Project (CGPP) through its partner Organization for Welfare and Development in Action (OWDA) enhanced the weak acute flaccid paralysis (AFP) surveillance by training and motivating community volunteers to conduct active community-based surveillance. The vaccination campaign was monitored and evaluated using independent monitors led by Jigjiga University in selected clusters (woredas) within Dollo Zone.

Data indicate that the immunisation campaign, which started through RR vaccination within 14 days of the laboratory-based verification, covered "a substantially high proportion of children." In the RR immunisation, an average of 91.4% of 0-11 months old and 90.2% of 12-59 months children were vaccinated. In SIA-1, the team vaccinated an average of 88% and 97%, and in SIA-2, 94.8% and 97.6% of children 0-11 months old and 12-59 months old, respectively. The active community-based surveillance of AFP revealed the existence of the disease in a sporadic form, of which two cases were found in Bokh district.

Although the outbreak response gave children a supplement to a previous vaccination, it also gave the mono-poliovirus immunisation for the first time for some children. During the RR, about 17% of children aged 0-11 months received vaccination for the first time. This first-time vaccination rate was as high as 55% in Bokh, about 16% in Warder, and 13% in Daratole. The average first-time coverage went down to 4.7% in the SIA-1 and 3.3% in SIA-2.

The independent monitoring group from Jigjiga University found that caregivers' awareness of the campaign's presence was adequate: 85% in Danoot and 92% in Bokh, where the outbreak occurred.

According to the analysis, the strengthening and formation of response teams at different levels of localities were important components of managing the response to the outbreak. "The relatively high vaccination coverage data during the rapid and the two supplementary immunization activities can create high herd immunity that could break the circulating poliovirus..."