An epidemiological investigation of a 4-month-old infant with VDPV1 paralytic poliomyelitis found no further viral spread, and a subsequent immunization campaign achieved >95% vaccine coverage.
Case Report (n=1)
No
Timely detection and public health response, including supplementary immunization, successfully prevented the spread of an ambiguous vaccine-derived poliovirus type 1 in a low-coverage area.
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. 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. 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. 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. Not applicable.
Yang et al. (Fri,) conducted a case report in Paralytic poliomyelitis caused by vaccine-derived poliovirus type 1 (VDPV1) (n=1). Epidemiological investigation and supplementary immunization activity was evaluated on Detection of VDPV in contacts, healthy children, or wastewater, and vaccination coverage. An epidemiological investigation of a 4-month-old infant with VDPV1 paralytic poliomyelitis found no further viral spread, and a subsequent immunization campaign achieved >95% vaccine coverage.