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The evidence on transmission dynamics of COVID-19 from pre- and asymptomatic cases: protocol for a systematic review. (Version 2 modified on 6 July 2021)

By Tom Jefferson, Annette Pluddemann, Elisabeth Spencer, Jon Brassey, Elena Cecilia Rosca, IGHO ONAKPOYA, David Evans, John Conly, Carl Heneghan

Posted 08 May 2021
medRxiv DOI: 10.1101/2021.05.06.21256615

Background The role of cases of SARS-CoV-2 who remain without symptoms throughout the active phase of the disease (asymptomatics) and those who have not developed symptoms yet when surveyed (pre-symptomatics) is at present unclear, despite the important role that they may play in infecting third parties. There is also a lack of clarity on the role of pauci-symptomatic persons with COVID-19 and the degree to which they may be associated with transmission compared to fully symptomatic persons. Methods We will search LitCovid, medRxiv, Google Scholar and the WHO Covid-19 database using Covid-19, SARS-CoV-2, transmission, and appropriate synonyms as search terms. We will also search the reference lists of included studies are searched for additional relevant studies. We will include studies of people exposed to SARS CoV-2 within 2-14 days (incubation time) of close contact or suspected community or institutional exposure to index asymptomatic infected individuals, as defined in each study with secondary case(s) infected. We will only include studies which provide microbiological proof of transmission outcome (culturable virus and /or genic sequencing). The inclusion of higher-quality evidence should overcome the methodological shortcomings of lower quality studies. We will assess quality of the chain of transmission evidence, microbiological proof and adequacy of follow up and symptom monitoring. Expected results We intend to present the evidence in three distinct packages: study description, methodological quality assessment and data extracted. We intend summarising the evidence and drawing conclusions

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