Impact of National Immunization Strategies on Vaccine-Preventable Diseases — China, 1950–2021

   A comprehensive 72-year study (1950–2021) in China has revealed significant reductions in the incidence of ten vaccine-preventable diseases (VPDs) due to varying national immunization strategies. Data on nine infectious diseases from China CDC and population figures from the UN were analyzed. Four national serosurveys (1980, 1992, 2006, 2014) assessed the prevalence of hepatitis B, highlighting the impact of vaccination on chronic infection rates. The study identified four stages: Pre-National Immunization Program (NIP) (1950–1977), Early NIP (1978–1987), Late NIP (1988–2007), and Expanded Program on Immunization (EPI) (2008–2021). During these stages, there was a cumulative average incidence of 230.8 cases per 100,000 population for nine VPDs. The majority (83.35%) occurred in the Pre-NIP stage, dramatically decreasing in subsequent stages. The EPI stage marked a significant decline in VPD incidences among children under five, except for pertussis, which increased by 63.77%. The study also noted a decrease in hepatitis B seroprevalence, particularly among children, post-vaccine introduction. However, it reported a modest decrease in mumps incidence and a re-emergence of pertussis cases. The research highlights the critical role of immunization in controlling VPDs, stressing the need for high vaccine coverage rates (VCRs) and optimized strategies for current and potential NIP inclusions. Limitations include variations in data accuracy and external factors like improved healthcare and living conditions, which may have influenced VPD decline.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.064

Thirty Years of Experience of Acute Flaccid Paralysis Surveillance for Polio — China, 1993–2022

   China's acute flaccid paralysis (AFP) surveillance system has been instrumental in maintaining the country's polio-free status for over two decades. A recent evaluation spanning 1993–2022 assessed the system's effectiveness in detecting poliovirus cases. During this period, the surveillance identified 95 cases of wild poliovirus and 24 cases due to vaccines among 150,779 reported AFP cases. The non-polio AFP detection rate consistently adhered to WHO standards, demonstrating the system's sensitivity. Key performance indicators, such as prompt investigation and stool specimen collection, have been consistently met, indicating proficiency in detecting poliovirus in China. While challenges remain in areas like case diagnosis and laboratory sample processing, the surveillance system has proven pivotal in China's fight against polio. As the world moves closer to global polio eradication, AFP surveillance will continue to play a crucial role in ensuring sustained absence of poliovirus transmission. Integrating AFP surveillance into a comprehensive disease monitoring framework and supplementing it with environmental and immunodeficiency-focused surveillance could further strengthen polio control efforts in China and worldwide.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.065

Comparison of Statistical Signal Detection Methods in Adverse Events Following Immunization — China, 2011–2015

   This study assessed the performance of various safety signal detection algorithms using adverse events following immunization (AEFI) data in China from 2011 to 2015. It sought to identify optimal methods and thresholds for routine vaccine safety surveillance. Employing spontaneous AEFI reports from the National Immunization Program Information System, the research analyzed 871,030 records, covering 41 vaccines and 771 specific AEFI events. Four signal detection methods — proportional reporting ratio (PRR), reporting odds ratio (ROR), Bayesian confidence propagation neural network (BCPNN), and multi-item gamma Poisson shrinker (MGPS) — were evaluated across different thresholds. The study observed significant variations in the number of signals detected by each method, with PRR and ROR identifying the most signals. Sensitivity and specificity analyses indicated that PRR, ROR, and BCPNN were more sensitive but less specific than MGPS. These findings suggest that the choice of signal detection method and threshold values should be tailored based on the severity and prevalence of AEFIs, as well as the vaccine type, to balance the risk of missing true safety signals against generating false positives. The study highlights the importance of data preparation and the need for further research to enhance vaccine safety signal detection accuracy in China.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.066

A Scoping Review of Real-World Study in Vaccine Evaluation

   A comprehensive review of real-world studies (RWS) on vaccines has highlighted their growing influence in post-2018 vaccine evaluation, particularly in high-income countries where reliable data is more accessible. With the FDA’s 2018 regulatory framework and the increased reliance on big data, evident through the spike in RWS publications, these studies offer critical insights into vaccine effectiveness, safety, and immunogenicity across diverse populations and in more varied real-life contexts than traditional clinical trials. The review shed light on the most common observational study designs employed, such as cohort and case-control studies, and the primary data sources, including administrative databases and electronic health records, consistently used in vaccine RWS. Emphasizing the emerging methods, such as the target trial emulation study design, the review also underscores the significance of robust and comprehensive data for assessing vaccine effectiveness in real-world settings. This review serves as a guide for researchers, showcasing the evolution of RWS in vaccine evaluation and underscoring the need for consistent standards and broader global participation, particularly from lower-income regions, to optimize vaccine RWS utilization.

   For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.067