6 September 2020 – Fourteen cases of vaccine-derived poliovirus type 1 (cVDPV1) have been detected in several districts in Saada governorate, in the north-west of Yemen.
The cases – children aged from 8 to 156 months – had onset of paralysis ranging from 31 January to 18 June 2020, with one other case from June 2019 also confirmed retrospectively.
The 14 cases are clustered in an area with very low routine immunization levels that has been inaccessible to the polio programme since late 2018 for various reasons, including the restrictions due to the current COVID-19 pandemic, and has been a source of growing concern for those reasons.
Health authorities in Yemen, supported by the polio programme staff, and the regional teams of WHO and UNICEF, are working hard to mount an outbreak response rapidly.
Contacts of affected children are being traced, and every effort is being made to ensure more children have access to essential immunization.
Vaccination is the only way to protect children from polio, and the oral polio vaccine (OPV) is the best know tool for that. It is the tool used by the WHO’s polio programme to eradicate polio and protect populations from type 1 polioviruses, in Yemen and worldwide.
Note on the vaccine-derived poliovirus
Vaccine-derived poliovirus type 1 is a strain of poliovirus that emerges and paralyses children in communities where not enough children have received OPV. The term “vaccine-derived poliovirus” can be misleading: while the vaccine-derived strains can cause outbreaks of polio, these outbreaks are stopped by achieving high vaccination coverage by the same vaccines. For this reason, an outbreak of VDPV acts as an urgent warning signal that immunity levels in that area are dangerously low.
