Papua New Guinea strengthens immunisation following detection of vaccine-derived poliovirus

Papua New Guinea (PNG) is responding to a new outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2), which was detected earlier this year in environmental samples and in healthy children from Lae City, Morobe Province. 

The outbreak marks the first detection of cVDPV2 since the country’s last circulating vaccine-derived poliovirus type 1 (cVDPV1) outbreak in 2018.

In April 2025, poliovirus type 2 was detected in Lae and later confirmed as cVDPV2 genetically linked to a strain previously found in Indonesia. Two healthy children also tested positive for the virus, and in August, the first paralysis case was confirmed in an unvaccinated 4-year-old boy. 

These detections prompted a nationwide response led by PNG’s National Department of Health, with support from World Health Organization (WHO), United Nations Children’s Fund (UNICEF), Australian Department of Foreign Affairs and Trade (DFAT) and NCIRS Global Health.

After declaring a national outbreak in May 2025, the government launched two rounds of supplementary immunisation activities (SIAs) using novel oral polio vaccine type 2 (nOPV2) and inactivated polio vaccine (IPV), targeting children under 10 years of age. 

The first immunisation round (SIA1) took place between August and September 2025. A post-SIA1 review held on 10–11 September 2025 brought together national health authorities and supporting partners to assess implementation, coverage, community engagement and the integration of routine immunisation activities. It also identified operational risks and cross-border implications for continued transmission.

Preparations are now underway for SIA2, alongside strengthened surveillance for acute flaccid paralysis (AFP) and environmental detection. Efforts continue to improve vaccination coverage and reinforce community trust in immunisation.

PNG was certified polio-free in 2000; however, persistent low immunisation coverage – particularly at the subnational level – has left communities vulnerable to disease re-emergence. 

In 2024, national coverage for the third dose of oral polio vaccine (OPV3) was reported at 44%, with some provinces falling below 40%. This immunity gap created conditions for vaccine-derived polioviruses to circulate and evolve.

With support from DFAT, NCIRS remains a key technical partner in outbreak response, contributing to assessments, surveillance strengthening and evaluation frameworks to inform future immunisation rounds.

As PNG works to close immunity gaps and halt poliovirus transmission, this collaborative response underscores the ongoing importance of regional coordination and sustained investment in routine immunisation to prevent the re-emergence of polio in the Western Pacific Region.