The outbreak was declared after a 3-year-old girl tested positive for vaccine-derived polio virus type 2.
The Philippines Department of Health (DOH) has declared an outbreak of polio after a case was confirmed in a young girl from Lanao del Sur.
The case was confirmed in a 3-year-old girl who presented with symptoms of acute flaccid paralysis on September 16. Tests confirmed that the child had vaccine-derived polio virus type 2 (VDPV2).
Environmental samples from sewage in Manila and waterways in Davao were confirmed to also contain the virus. VDPV2 was isolated from 2 of the environmental samples and genetically linked to isolates from the child. As a result, VDVP2 was classified as circulating.
The last known case of wild poliovirus recorded in the Philippines was in 1993. The country was declared wild polio-free in 2000 along with the rest of the World Health Organization’s (WHO) Western Pacific Region.
“We are very concerned that polioviruses are now circulating in Manila, Davao, and Lanao del Sur,” Rabindra Abeyasinghe, a WHO representative in the Philippines, said in the statement. “WHO and UNICEF are working closely with the Department of Health to strengthen surveillance and swiftly respond to this outbreak. We urge all parents and caregivers of children under 5 years of age to have them vaccinated so that they are protected against polio for life.”
According to a situation report issued by the WHO and UNICEF, wild poliovirus type 2 was certified as globally eradicated in 2015. Children become susceptible to polioviruses—both vaccine-derived or wild-type—when immunization activities are not conducted properly or too few children receive all 3 required doses of the vaccine. Full immunization provides protection for both forms of the virus.
Polio vaccination coverage has been steadily declining in the Philippines over the past few years. In order to half the spread of polio, at least 95% of children under the age of 5 years need to be fully vaccinated. Prior to the outbreak declaration, the DOH launched a polio immunization campaign and indicates that further mass polio vaccination rounds will be rolled out in October.
In April 2016, the trivalent oral polio vaccine was withdrawn and replaced with the bivalent oral polio vaccine (bOPV) as part of the Global Polio Eradication Initiative. This change removed the type 2 component (OPV2) from immunization programs due to the continued emergence of type 2 VDPVs, despite eradication of wild polio virus type 2 in 1999.
In August when environmental samples in Manila tested positive for VDVP1, a synchronized vaccination campaign was launched and immunized 53.8% of targeted children aged 0-59 months with bOPV between August 19-31.
In 2018, the estimated vaccination coverage for children under 1 year with 3 doses of bOPV was 66%. Coverage for the inactivated poliovirus vaccine has been below 50% since it was first introduced in 2016 and is currently at 23% for 2019.
“The outbreak calls for urgent action to protect more children from being infected. It reminds us of the importance of increasing immunization coverage to 95% of children to stop polio virus transmission in the Philippines,” UNICEF Philippines representative Oyun Dendevnorov said in the statement.