Timely detection and response prevented further spread and development of a circulating VDPV type 1 (cVDPV1) and rapidly raised population immunity in a low-coverage area through a high-quality SIA and interrupted spread of the virus.
Abstract
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.
Since the establishment of the Global Polio Eradication Initiative (GPEI) in 1988, wild poliovirus type 1 (WPV1) remains endemic in only Afghanistan and Pakistan. However, outbreaks of paralytic polio caused by circulating vaccine-derived polioviruses (cVDPVs) emerge in areas with low vaccination coverage and continue to challenge polio eradication goals. As the Global Polio Eradication Initiative extends its eradication target to 2029, understanding the epidemiologic, surveillance, and operational factors associated with persistent transmission is critical for informing policy decisions and targeting limited resources. This report describes global polio immunization efforts, surveillance activities, and epidemiology during January 2023–December 2024.
Surveillance and virologic data were obtained from the World Health Organization’s (WHO) global Polio Information System (POLIS), and immunization coverage estimates were sourced from WHO’s Immunization Dashboard, which incorporates administrative and survey-based data from WHO and UNICEF. A cVDPV outbreak was defined using standardized acute flaccid paralysis (AFP) and environmental surveillance criteria; analyses were conducted in R (version 4.4.1).
Afghanistan and Pakistan reported 99 WPV1 cases in 10 provinces in 2024, compared with 12 cases in 3 provinces in 2023. cVDPV cases decreased 12% from 529 in 2023 to 464 in 2024. However, cVDPV detections from AFP and environmental surveillance expanded geographically, with detections in 40 countries in Africa, Southeast Asia, the Middle East and Europe in 2024, including 14 countries with no detections in 2023. The resurgence of WPV1 in polio-free regions in Afghanistan and Pakistan and the spread of cVDPVs challenge global polio eradication.
Achieving global polio eradication will require reaching persistently missed children in remote and insecure areas, strengthening vaccination and surveillance systems, and reinforcing accountability to improve campaign quality. The geographic expansion of cVDPV type 2 (cVDPV2) underscores the need for rapid detection, expanded nOPV2 use in areas with prolonged transmission, and sustained partner engagement and strategic resource allocation amid declining global health funding.
H. Whitmire, M. Z. Wadood, Ina G. Storm et al.· Archives of Public Health· 0 citations
INTRODUCTION
From 2020 to 2023, Madagascar experienced an outbreak of circulating vaccine-derived poliovirus type 1 (cVDPV1) that notably affected adults and was associated with high mortality among paralytic cases. This atypical epidemiological pattern required adapted surveillance approaches and tailored outbreak response strategies, including vaccination campaigns targeting adult populations.
METHODS
We conducted a descriptive analysis of the cVDPV1 outbreak in Madagascar between September 2020 and September 2023. Epidemiological data on confirmed and polio-compatible cases were reviewed, including age distribution, clinical presentation, and outcomes. We also documented outbreak response strategies, particularly vaccination campaigns and operational innovations implemented to reach adult populations.
RESULTS
A total of 54 confirmed cases of paralytic polio caused by cVDPV1 were reported during the study period, including two adults presenting with fever and paralysis. Between February 2022 and March 2023, 15 adult acute flaccid paralysis cases were classified as polio-compatible by the National Polio Eradication Committee due to missing (86%) or negative laboratory specimens. Mortality among these compatible adult cases was 56%. In response, Madagascar conducted vaccination campaigns using bivalent oral polio vaccine, targeting the entire population in four regions and children under 15 years in the rest of the country. Critical role of country leadership, strategic mobilization, and effective communication in driving success and influencing risk perception during the 2023 campaigns helped achieve high coverage among adults.
CONCLUSIONS
The cVDPV1 outbreak in Madagascar demonstrated the potential for significant adult involvement and high mortality in polio outbreaks. High vaccination coverage combined with targeted innovations and strong community engagement contributed to successful outbreak control. These findings highlight the importance of inclusive vaccination strategies and tailored approaches in similar settings.
Kpandja Djawe, Eric Aigbogun, Joseph Souba Zoumanigui et al.· Vaccine· 0 citations
BACKGROUND
In 2023, novel oral polio vaccine type 2 (nOPV2) was used to respond to an outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2) in Kenya. We assessed the immunogenicity of one and two doses of nOPV2 administered during outbreak response.
METHODS
An observational cohort study was conducted from October to December 2023 in Kitui and Tana River counties in Kenya. Children aged 6-59 months were enrolled. Two nOPV2 doses were administered. Dried blood spots (DBS) were collected at enrollment, four-weeks after the first nOPV2 dose, and two- and four-weeks after the second nOPV2 dose. The DBS cards were tested at the US Centers for Disease Control and Prevention (CDC), Atlanta for the presence of poliovirus neutralizing antibodies using microneutralization assays. The primary endpoint was cumulative immune response after two nOPV2 doses.
FINDINGS
Of the 475 participants followed in the study, 461 (97%) completed all study visits and were included in the analysis. Four weeks after two nOPV2 doses, a cumulative type 2 immune response was observed in 285 (62%; 95% CI 57-66) of 461 participants. After one nOPV2 dose, type 2 immune response was observed in 196 (43%, 95% CI 38-47) of 461 participants. Type 2 seropositivity (titers ≥1:8) increased from 19% at enrollment to 72% after two nOPV2 doses.
INTERPRETATION
The study demonstrated an immune response in 62% of the participants following two nOPV2 outbreak vaccination rounds. These findings suggest that two nOPV2 doses may be insufficient to achieve high population immunity during poliovirus type 2 outbreak response in sub-Saharan Africa.
A. Anand, Damaris Jepkosgei, C. Mwachari et al.· Vaccine· 0 citations
A novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic outbreak started in Wuhan City, Hubei
Province, China, in December 2019 and subsequently spread globally with a 3.4% mortality rate of 87,137 confirmed
cases as of March 1, 2020 and currently in February 16, 2024 it caused 0.9% mortality rate of 703,305,215 nationwide
confirmed cases [1,2]. The coronavirus disease 2019, or COVID-19, was named the disease by the World Health
Organization (WHO) and poses a significant threat to public health, including Malaysia. The virus’s global spread was
attributed to sustained human-to-human transmission, leading to exported cases worldwide and WHO announced it as
a pandemic on March 11, 2020 [1,3,4].
It is a newly discovered novel strain of coronavirus detected on December 31, 2019 [1]. Utilising the angiotensinconverting enzyme 2 (ACE2) receptor, like SARS-CoV, the virus predominantly spreads through the respiratory tract [5].
Clinical symptoms exhibited by COVID-19 patients included fever, cough, fatigue, and, in some cases, gastrointestinal
infection symptoms [6]. Vulnerability to infection and a propensity for severe outcomes, such as acute respiratory
distress syndrome (ARDS) and cytokine storms, were observed notably in the elderly and those with underlying diseases
[7]. The SARS-CoV-2 was initially treated as secondary and tertiary prevention under the level of disease prevention
aiming for early diagnosis from prompt, optimised and sustained care, rehabilitation, and disability prevention [8].
Subsequently, when the virus characteristic was established the prevention level focused on primordial and primary
prevention, including the health education, health promotion, new vaccine development and immunisation [8].
Maznieda Mahjom, Imanul Hassan Abdul Shukor, M. Arip et al.· International Journal of Tel...· 0 citations
BACKGROUND
Meningococcal meningitis remains a major public health challenge in Africa's meningitis belt despite the successful elimination of serogroup A epidemics following MenAfriVac introduction. Outbreaks caused by serogroups C, W, and X persist. NmCV-5, a pentavalent conjugate vaccine targeting serogroups A, C, W, Y, and X, was prequalified by WHO in 2023 and used in Niger during reactive vaccination campaigns in 2024.
METHODS
We conducted a matched case-control study in six health districts in Niger (Niamey IV and Magaria) to estimate NmCV-5 effectiveness against meningococcal meningitis. Cases were individuals with PCR-confirmed meningococcal meningitis, aged 1-19 years, resident in the vaccination campaign area, and presenting with symptom onset ≥10 days post-campaign. Enrollment took place between May 2024 and July 2025. Four age-, sex-, and residence-matched community controls were enrolled per case. Vaccination status was verified by patient-retained vaccination card when available or self-reported. Logistic regression was used to calculate crude and adjusted vaccine effectiveness (VE).
RESULTS
17 confirmed cases (14 NmC, 3 NmW) and 68 matched community controls were enrolled in the study. Seven cases (41%) and 58 controls (86%) reported NmCV-5 vaccination; vaccination status of all cases and 8 of 58 (14%) controls was confirmed by vaccination card. Crude VE against all meningococcal meningitis was 88% (95% CI: 62-96), and against NmC specifically was 86% (95% CI: 50-96). Adjusted for household crowding and history of recent respiratory infections, VE was 92% (95% CI: 72-98) overall and 91% (95% CI: 63-98) for NmC. Sensitivity analyses confirmed robustness of estimates under extreme assumptions.
CONCLUSIONS
NmCV-5 demonstrated high effectiveness against circulating meningococcal strains NmC and NmW in real-world outbreak conditions. Limitations include small sample size, reliance on self-reported vaccination status, and absence of cases from other serogroups. Further studies should assess long-term impact on carriage and effectiveness against invasive disease across all targeted serogroups.
Laura V Cooper, Médard Djedanem, Assan Abdoul Nasser et al.· Vaccine· 0 citations
Although the immunization program requires OPV vaccine for every infant, outbreaks of polio and Acute Flaccid Paralysis (AFP) still occur frequently, triggering a rapid response of mass immunization. The vaccine of Inactivated Polio Virus (IPV) was added to prevent wild poliovirus which causes paralysis, but its effectiveness has not been optimal. The study purpose was to analyse the effect of child characteristics, perceptions, parental hygiene practices, and house's physical conditions on the IPV vaccination utilization. This study was quantitative survey with a cross-sectional approach. The population was all children aged <7 years in Central Java Province. A sample of 1,069 children was obtained through convenience sampling from 15 districts/cities serving as RCA locus for 2024 Polio SubPIN activities. Data collection was conducted through observations using the KIA Handbook, home visits, and interviews using a questionnaire. Data was analysed using descriptive, bivariate, and multivariate. The results showed that 85.9% of children utilized 4-doses OPV vaccination completely and 83.6% utilized the first dose of IPV vaccination. It was proven that OPV immunization status, parental hygiene practices, and house's physical condition were associated with IPV vaccine utilization, both partially and simultaneously. The effect of three variables was 27%, with OPV immunization status being the main predictor. There was a 3.54-fold increase in IPV utilization if OPV status was complete, followed by parental hygiene (OR=2.02) and the house's physical condition (OR=1.56). More intensive socialization regarding IPV vaccination is needed through personal communication interventions that can also motivate parents. Strengthening the vaccination service system by providing vaccine stocks and cold chains as needed, regulatory support, and effective IEC are key factors in the success of IPV vaccination
T. Hardiyanti, Ayun Sriatmi, Martini et al.· Jurnal kesehatan masyarakat· 0 citations
