The SARS-CoV-2 pandemic has infected millions of people globally and continues to spread rapidly in many countries. As global vaccine access remains limited, SARS-CoV-2 transmission can be reduced through non-pharmaceutical interventions (NPIs), such as social distancing and lockdown measures that limiting human contact by restricting human mobility, and diagnostic testing strategies that rapidly identify and isolate infectious individuals. In this dissertation, I conducted three studies that inform SARS-CoV-2 surveillance and control policies in low- and middle-income countries (LMICs).
The first study focuses in South Africa, where there have been multiple lockdowns and COVID-19 resurgences since the start of the pandemic.1 I assessed the association between mobility, as measured by smartphone data, and SARS-CoV-2 case positivity in South African provinces and districts at the ecological-level using regression, cross-correlation and interrupted time series analysis. I found that increases in mobility were positively associated with future COVID-19 incidence aggregated at both the province and district-level, and the association of mobility and COVID-19 incidence remained even when adjusted for district-level confounders.
The second and third studies focus on rapid antigen testing (Ag-RDTs) in general LMIC settings. The main outcomes for these two studies include impact, defined as the percentage of infections averted compared to the base case scenario for each use case, and efficiency, defined as the number of tests needed to avert one infection compared to the base case scenario across use cases. In the second study, I quantified impact and efficiency of Ag-RDTs for population-level community testing using a compartmental model in a general population of 10 million people. This study adds to the literature that Ag-RDTs can be a valuable tool for population-level SARS-CoV-2 surveillance and case detection when testing is frequent and widespread, and diagnosis must be accompanied by corresponding reduction in post-diagnosis contacts in order for testing to be effective. I also identified that community testing is most useful when an epidemic is waning or before an epidemic wave, which is when SARS-CoV-2 prevalence and Rt are low.
Finally, the third study assessed efficiency and impact of SARS-CoV-2 Ag-RDT testing strategies by comparing eight mathematical models across several scenarios, hereafter referred to as “use cases”. There was a clear trade-off between impact and efficiency; increasing test frequency (and/or more widespread testing of a community) increased impact, but consequently decreased efficiency. Additionally, testing strategies across most scenarios had the greatest impact when Rt and/or infection prevalence were low, but were least efficient.
The findings from this dissertation provide further evidence of the importance of public health mitigation and control measures that reduce SARS-CoV-2 spread, such as NPIs and diagnostic testing, particularly in LMICs that have limited access to COVID-19 vaccines. The evidence generated from these studies can be used for future SARS-CoV-2 resurgences, whether from currently circulating variants, emergence of new SARS-CoV-2 variant strains or adaptation for use in future infectious disease outbreaks.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/44453 |
| Date | 18 May 2022 |
| Creators | Sy, Karla Therese L. |
| Contributors | Horsburgh, Jr., C. Robert |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution-NonCommercial-NoDerivatives 4.0 International, http://creativecommons.org/licenses/by-nc-nd/4.0/ |
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