One new case of circulating vaccine-derived poliovirus type 1 (cVDPV1) was reported in the past week in Madagascar, with onset of paralysis on 22 August from Sud-Ouest province, according to the Global Polio Eradication Initiative (GPEI).
This brings the total number of cVDPV1 cases for 2015 to ten.
The 2015 cases are genetically linked to the case reported in September 2014, indicating prolonged and widespread circulation of the virus.
The GPEI defines Vaccine-derived polioviruses (VDPVs) as follows: The oral polio vaccine (OPV) contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus.
OPV and inactivated polio vaccine (IPV) have important but distinct advantages, and both vaccines are necessary to end polio for good. Because OPV protects both the individual and the community, it has been an essential tool for countries working to stop wild poliovirus transmission.
IPV eliminates the risk of cVDPV, and thus is vital to end polio once and for all. As part of the polio eradication endgame, all countries will stop OPV use and transition to IPV. With support from the GPEI and Gavi, the 126 remaining OPV-only countries have plans to introduce at least one dose of IPV into their routine immunization programs by the end of 2015.
There has been 15 cVDPV cases reported globally so far in 2015: Madagascar (10), Ukraine (2), Laos (1), Guinea (1) and Nigeria (1).