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The impact of supplementary immunization activities on measles transmission dynamics and implications for measles elimination goals: A mathematical modelling study

•We study the impact of supplementary immunization activities (SIAs) on the measles transmission dynamics and its implications for measles elimination goals in China.•The model takes into account population demographics, age-specific contact patterns, seasonality, routine vaccination, SIAs, and the...

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Published in:Journal of theoretical biology 2022-11, Vol.551-552, p.111242-111242, Article 111242
Main Authors: Shen, Mingwang, Sun, Xiang, Xiao, Yanni, Liu, Yuanbao, Wang, Congyue, Wang, Zhiguo, Rong, Libin, Peng, Zhihang
Format: Article
Language:English
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Summary:•We study the impact of supplementary immunization activities (SIAs) on the measles transmission dynamics and its implications for measles elimination goals in China.•The model takes into account population demographics, age-specific contact patterns, seasonality, routine vaccination, SIAs, and the waning vaccine-induced immunity.•SIAs have greatly reduced the measles incidence and the fraction of susceptibles, but the benefit may wane over time. Additional SIAs may accelerate the measles elimination.•The outbreak risk may be greater than 70% once the monthly imported measles cases exceed ten. Measles has re-emerged globally due to the accumulation of susceptible individuals and immunity gap, which causes challenges in eliminating measles. Routine vaccination and supplementary immunization activities (SIAs) have greatly improved measles control, but the impact of SIAs on the measles transmission dynamics remains unclear as the vaccine-induced immunity wanes. We developed a comprehensive measles transmission dynamics model by taking into account population demographics, age-specific contact patterns, seasonality, routine vaccination, SIAs, and the waning vaccine-induced immunity. The model was calibrated by the monthly age-specific cases data from 2005 to 2018 in Jiangsu Province, China, and validated by the dynamic sero-prevalence data. We aimed to investigate the short-term and long-term impact of three-time SIAs during 2009–2012 (9.68 million and 4.25 million children aged 8 months-14 years in March 2009 and September 2010, respectively, and 140,000 children aged 8 months-6 years in March 2012) on the measles disease burden and explored whether additional SIAs could accelerate the measles elimination. We estimated that the cumulative numbers of measles cases from March 2009 to December 2012 (in the short run) and to December 2018 (in the long run) after three-time SIAs (base case) were 6,699 (95% confidence interval [CI]: 2,928–10,469), and 22,411 (15,146–29,675), which averted 45.0% (42.9%-47.0%) and 34.3% (30.7%-37.9%) of 12,226 (4,916–19,537) and 34,274 (21,350–47,199) cases without SIAs, respectively. The fraction of susceptibles for children aged 8–23 months and 2–14 years decreased from 8.3% and 10.8% in March 2009 to 5.8% and 5.8% in April 2012, respectively. However, the fraction of susceptibles aged 15–49 years and above 50 years increased gradually to about 15% in 2018 irrespective of SIAs due to the waning immunity. The measles elimination goa
ISSN:0022-5193
1095-8541
DOI:10.1016/j.jtbi.2022.111242