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Updated: Aug 6, 2026
Particle Agglutination Method for Poliovirus Identification
Published on: April 20, 2011
Response to a vaccine-derived poliovirus type 1 event - Sichuan, China, 2024
Qing Yang1, Jiajie Liu2, Yi Liu2
1Sichuan Center for Disease Control and Prevention, No.6 Zhongxue Road, Wuhou District, Chengdu, 610041, China. Yq_911001@163.com.
Insights
A vaccine-derived poliovirus type 1 (VDPV1) caused paralytic polio in an infant in China. Rapid response and vaccination efforts prevented further spread of this ambiguous VDPV1 outbreak.
Area of Science:
- Epidemiology
- Virology
- Public Health
Background:
- A case of paralytic poliomyelitis in a 4-month-old infant in Sichuan, China, was linked to vaccine-derived poliovirus type 1 (VDPV1).
- This marked the third VDPV outbreak detected via acute flaccid paralysis (AFP) surveillance in the region since 2012.
- The study details the epidemiological investigation and response to this VDPV1 event.
Purpose of the Study:
- To investigate an outbreak of paralytic poliomyelitis caused by VDPV1 in Sichuan, China.
- To implement control measures to prevent further poliovirus transmission.
- To assess the effectiveness of public health interventions in a low-vaccination coverage area.
Main Methods:
- Conducted epidemiological investigation following WHO and China's National Health Commission guidelines.
- Performed case and virus verification, including poliovirus screening in contacts, healthy children, and wastewater.
- Implemented active surveillance for AFP cases and conducted supplementary immunization activities (SIAs) with catch-up vaccination.
Main Results:
- The infant's paralysis was confirmed as VDPV1, differing by 10-15 nucleotides from the Sabin type 1 strain.
- No VDPV transmission was detected among contacts, in healthy children, wastewater, or through active AFP surveillance.
- Post-SIA, bivalent live attenuated polio vaccine coverage reached 95.4% (4 months-4 years) and full-series coverage reached 98.5% (5-14 years).
Conclusions:
- The identified VDPV1 was classified as ambiguous (aVDPV1), and timely interventions averted a circulating VDPV1 (cVDPV1) outbreak.
- Low vaccination coverage and poor sanitation were identified as contributing factors to the aVDPV1 emergence.
- Information technology-supported vaccination strategies rapidly increased population immunity and interrupted virus spread.
Background:
In September 2024, a 4-month-old infant in Liangshan, Sichuan, China was diagnosed with paralytic poliomyelitis that turned out to have been caused by a vaccine-derived poliovirus type 1 (VDPV1). This was the third VDPV outbreak detected by routine acute flaccid paralysis (AFP) surveillance in Sichuan since 2012. We conducted an epidemiological investigation into the event and implemented response measures to prevent further viral spread.
Methods:
The investigation and response were conducted according to World Health Organization (WHO) and China's National Health Commission standard operating procedures. Measures included case and virus verification; search for poliovirus among contacts, healthy children, and in wastewater; active surveillance for AFP cases in health facilities and communities; vaccination coverage assessment; and supplementary immunization activity (SIA) and catch-up vaccination.
Results:
The paralyzed infant was determined to be a VDPV1 case by the Sichuan provincial expert group; the VDPV1 had 10-15 nucleotide changes from Sabin strain type 1. No VDPVs were found in close contacts, healthy children, or wastewater; no AFP cases were found in health facilities or communities; no local circulation of the VDPV1 was detected. Following a county-wide SIA with catch-up vaccination, 2-dose, bivalent live attenuated polio vaccine coverage was 95.4% among children four months to four years of age, and full-series polio vaccine coverage was 98.5% in children 5-14 years of age.
Conclusions:
The VDPV was an ambiguous VDPV type 1 (aVDPV1). Timely detection and response prevented further spread and development of a circulating VDPV type 1 (cVDPV1). Low vaccination coverage and poor sanitation were contributing factors to the emergence of the aVDPV1. Information technology facilitated the strategy of "Government Locates, Health Vaccinates" that rapidly raised population immunity in a low-coverage area through a high-quality SIA and interrupted spread of the virus.
Clinical Trial Number:
Not applicable.
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