Poliovirus serological assay after the cVDPV1 outbreak in Papua New Guinea: a cross-sectional study from 2020 to 2021

Abstract

Background: In June 2018, a type 1 circulating vaccine-derived poliovirus (cVDPV1) outbreak was declared in Papua New Guinea (PNG), resulting in a total of 26 paralytic confirmed cases. Eight vaccination campaign rounds with bivalent oral poliovirus vaccine (bOPV) were carried out in response. Prevalence of neutralizing polio antibodies in children was assessed two years after the outbreak response was completed.

Methods: We conducted a cross-sectional serological survey among children aged 6 months-10 years selected from six provinces in PNG to evaluate seroprevalence of neutralizing polio antibodies to the three poliovirus serotypes and analyse sociodemographic risk factors.

Findings: We included 984 of 1006 enrolled children in the final analysis. The seroprevalence of neutralizing polio antibodies for serotype 1, 2 and 3 was 98.3% (95% CI: 97.4-98.9), 63.1% (95% CI: 60.1-66.1) and 95.0% (95% CI: 93.6-96.3), respectively. Children <1 year had significantly lower type 1 seroprevalence compared to older children (p < 0.001); there were no significant differences in seroprevalence among provinces.

Interpretation: PNG successfully interrupted transmission of cVDPV1 with several high coverage bOPV campaigns and seroprevalence remained high after two years. The emergence of cVDPV strains underscores the importance of maintaining high levels of routine immunization coverage and effective surveillance systems for early detection.

Funding: World Health Organization through a Rotary International IPPC grant.

Keywords: Bivalent oral poliovirus vaccine; Outbreak response; Papua New Guinea; Polio; Seroprevalence; Vaccine-derived poliovirus.

Fig. 1

Map of Papua New Guinea showing the provinces with cVDPV1 cases resulting from the 2018 outbreak. The cVDPV1 reports include cases of acute flaccid paralysis and contact cases. The shaded provinces were included in this seroprevalence survey and include Simbu, Madang, Morobe, Eastern Highlands, National Capital District (NCD), and Central. The sample size enrolled from each province is indicated. cVDPV1, type 1 circulating vaccine-derived poliovirus.

Fig. 2

Seroprevalences with 95% CIs by age categories. Children born between January 2010 and December 2020. PV, poliovirus.

Fig. 3

Seroprevalences with 95% CIs by province. Children were born between January 2010 and December 2020. The bar width is proportional to the sample size from each province. The number of bOPV SIAs conducted in each province is indicated. bOPV, bivalent oral poliovirus vaccine; PV, poliovirus; SIA, supplementary immunization activity.

Fig. 4

Reverse cumulative distribution for all three poliovirus serotypes from 6 months to 10 years of age. The results show significantly higher type 1 titres as compared to titres of types 2 and 3 (p < 0.01 each, respectively) and distribution of type 3 titre is significantly higher than type 2 titre distribution (p < 0.01).