Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China
Abstract By 31 May 2022, original/Alpha, Delta and Omicron strains induced 101 outbreaks of COVID-19 in mainland China. Most outbreaks were cleared by combining non-pharmaceutical interventions (NPIs) with vaccines, but continuous virus variations challenged the dynamic zero-case policy (DZCP), posi...
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| Format: | Article |
| Language: | English |
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BMC
2023-06-01
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| Series: | BMC Public Health |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s12889-023-16009-8 |
| _version_ | 1827928417422540800 |
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| author | Sanyi Tang Xia Wang Biao Tang Sha He Dingding Yan Chenxi Huang Yiming Shao Yanni Xiao Robert A. Cheke |
| author_facet | Sanyi Tang Xia Wang Biao Tang Sha He Dingding Yan Chenxi Huang Yiming Shao Yanni Xiao Robert A. Cheke |
| author_sort | Sanyi Tang |
| collection | DOAJ |
| description | Abstract By 31 May 2022, original/Alpha, Delta and Omicron strains induced 101 outbreaks of COVID-19 in mainland China. Most outbreaks were cleared by combining non-pharmaceutical interventions (NPIs) with vaccines, but continuous virus variations challenged the dynamic zero-case policy (DZCP), posing questions of what are the prerequisites and threshold levels for success? And what are the independent effects of vaccination in each outbreak? Using a modified classic infectious disease dynamic model and an iterative relationship for new infections per day, the effectiveness of vaccines and NPIs was deduced, from which the independent effectiveness of vaccines was derived. There was a negative correlation between vaccination coverage rates and virus transmission. For the Delta strain, a 61.8% increase in the vaccination rate (VR) reduced the control reproduction number (CRN) by about 27%. For the Omicron strain, a 20.43% increase in VR, including booster shots, reduced the CRN by 42.16%. The implementation speed of NPIs against the original/Alpha strain was faster than the virus’s transmission speed, and vaccines significantly accelerated the DZCP against the Delta strain. The CRN ( $${R}_{c1}$$ R c 1 ) during the exponential growth phase and the peak time and intensity of NPIs were key factors affecting a comprehensive theoretical threshold condition for DZCP success, illustrated by contour diagrams for the CRN under different conditions. The DZCP maintained the $${R}_{c1}$$ R c 1 of 101 outbreaks below the safe threshold level, but the strength of NPIs was close to saturation especially for Omicron, and there was little room for improvement. Only by curbing the rise in the early stage and shortening the exponential growth period could clearing be achieved quickly. Strengthening China's vaccine immune barrier can improve China's ability to prevent and control epidemics and provide greater scope for the selection and adjustment of NPIs. Otherwise, there will be rapid rises in infection rates and an extremely high peak and huge pressure on the healthcare system, and a potential increase in excess mortality. |
| first_indexed | 2024-03-13T06:07:18Z |
| format | Article |
| id | doaj.art-697aa866318642da90b369972e95cb69 |
| institution | Directory Open Access Journal |
| issn | 1471-2458 |
| language | English |
| last_indexed | 2024-03-13T06:07:18Z |
| publishDate | 2023-06-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Public Health |
| spelling | doaj.art-697aa866318642da90b369972e95cb692023-06-11T11:27:43ZengBMCBMC Public Health1471-24582023-06-0123111210.1186/s12889-023-16009-8Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in ChinaSanyi Tang0Xia Wang1Biao Tang2Sha He3Dingding Yan4Chenxi Huang5Yiming Shao6Yanni Xiao7Robert A. Cheke8School of Mathematics and Statistics, Shaanxi Normal UniversitySchool of Mathematics and Statistics, Shaanxi Normal UniversityCenter for Intersection of Mathematics and Life Sciences, Xi’an Jiaotong UniversitySchool of Mathematics and Statistics, Shaanxi Normal UniversitySchool of Mathematics and Statistics, Shaanxi Normal UniversitySchool of Mathematics and Statistics, Shaanxi Normal UniversityBeijing Changping LaboratoryCenter for Intersection of Mathematics and Life Sciences, Xi’an Jiaotong UniversityNatural Resources Institute, University of Greenwich at Medway, Central Avenue, Chatham MaritimeAbstract By 31 May 2022, original/Alpha, Delta and Omicron strains induced 101 outbreaks of COVID-19 in mainland China. Most outbreaks were cleared by combining non-pharmaceutical interventions (NPIs) with vaccines, but continuous virus variations challenged the dynamic zero-case policy (DZCP), posing questions of what are the prerequisites and threshold levels for success? And what are the independent effects of vaccination in each outbreak? Using a modified classic infectious disease dynamic model and an iterative relationship for new infections per day, the effectiveness of vaccines and NPIs was deduced, from which the independent effectiveness of vaccines was derived. There was a negative correlation between vaccination coverage rates and virus transmission. For the Delta strain, a 61.8% increase in the vaccination rate (VR) reduced the control reproduction number (CRN) by about 27%. For the Omicron strain, a 20.43% increase in VR, including booster shots, reduced the CRN by 42.16%. The implementation speed of NPIs against the original/Alpha strain was faster than the virus’s transmission speed, and vaccines significantly accelerated the DZCP against the Delta strain. The CRN ( $${R}_{c1}$$ R c 1 ) during the exponential growth phase and the peak time and intensity of NPIs were key factors affecting a comprehensive theoretical threshold condition for DZCP success, illustrated by contour diagrams for the CRN under different conditions. The DZCP maintained the $${R}_{c1}$$ R c 1 of 101 outbreaks below the safe threshold level, but the strength of NPIs was close to saturation especially for Omicron, and there was little room for improvement. Only by curbing the rise in the early stage and shortening the exponential growth period could clearing be achieved quickly. Strengthening China's vaccine immune barrier can improve China's ability to prevent and control epidemics and provide greater scope for the selection and adjustment of NPIs. Otherwise, there will be rapid rises in infection rates and an extremely high peak and huge pressure on the healthcare system, and a potential increase in excess mortality.https://doi.org/10.1186/s12889-023-16009-8COVID-19Non-pharmaceutical interventionsMathematical modelEpidemic wavesMitigationChina |
| spellingShingle | Sanyi Tang Xia Wang Biao Tang Sha He Dingding Yan Chenxi Huang Yiming Shao Yanni Xiao Robert A. Cheke Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China BMC Public Health COVID-19 Non-pharmaceutical interventions Mathematical model Epidemic waves Mitigation China |
| title | Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China |
| title_full | Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China |
| title_fullStr | Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China |
| title_full_unstemmed | Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China |
| title_short | Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China |
| title_sort | threshold conditions for curbing covid 19 with a dynamic zero case policy derived from 101 outbreaks in china |
| topic | COVID-19 Non-pharmaceutical interventions Mathematical model Epidemic waves Mitigation China |
| url | https://doi.org/10.1186/s12889-023-16009-8 |
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