On May 9, 2025, Papua New Guinea, through its national authority under the International Health Regulations, urgently informed the World Health Organization that circulating vaccine-derived poliovirus type 2 (cVDPV2) had been detected in fecal samples from two healthy children in Morobe Province. Given the low coverage rate of routine immunization in this country, the potential risk of virus transmission locally has significantly increased.
The process of case discovery
This discovery originated from an in-depth environmental monitoring and epidemiological investigation. On April 10, 2025, staff members collected fecal samples from 25 healthy children in the Laicheng Environmental Monitoring catchment Area. On May 8th, the World Health Organization’s Australian Polio Regional Reference Laboratory confirmed that two of the children’s samples were positive for cVDPV2. These two children come from different villages within the catchment area and showed no symptoms when samples were collected.
Virus Characteristics and Risks
Poliomyelitis is a highly contagious disease that mainly affects children under the age of five and may lead to permanent paralysis or even death. Vaccine-derived poliovirus is formed after genetic mutation of the attenuated virus in the oral polio vaccine (OPV) in the human body. In communities with low immunization coverage, this virus is likely to continue to spread and undergo further mutations. The cVDPV2 detected in Papua New Guinea this time has a genetic link with the virus strain that previously caused the epidemic in Indonesia and is not related to the cVDPV1 outbreak in the country in 2018, indicating a new transmission risk.
Current situation of immunization coverage
The polio vaccination coverage rate in Papua New Guinea has been unsatisfactory. As of 2024, the vaccination rate of the third dose of oral polio vaccine (OPV3) across the country was only 44%. In Morobe Province, the coverage rate of bivalent oral poliomyelin (bOPV) has remained below 40% over the past five years, while the coverage rate of the first dose of inactivated polio vaccine (IPV1) is only between 52% and 54%. However, the vaccination coverage rate in Lai City is relatively high, with 73% for bOPV and 90% for IPV1.
Public health response measures
In response to this epidemic, Papua New Guinea promptly activated national and provincial emergency operation centers and strengthened acute flaccid paralysis (AFP) and environmental monitoring to closely monitor the spread of the virus. Meanwhile, the catch-up vaccination campaign of IPV vaccine has been accelerated nationwide to reduce the risk of paralysis in children. Furthermore, the country has also closely collaborated with partners of the Global Polio Eradication Initiative (GPEI) to make technical preparations for the use of OPV2 in targeted immune responses. In terms of cross-border coordination, Papua New Guinea has also taken corresponding measures to conform to the regional risk mitigation strategy and promptly informed the international community of the latest situation of the epidemic through the mechanism of the International Health Regulations.
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