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Replacement dynamics and the pathogenesis of the Alpha, Delta and Omicron variants of SARS-CoV-2
- Thomas Ward, Alex Glaser, Christopher E. Overton, Bob Carpenter, Nick Gent, Anna C. Seale
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- Journal:
- Epidemiology & Infection / Volume 151 / 2023
- Published online by Cambridge University Press:
- 20 December 2022, e32
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- Article
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New SARS-CoV-2 variants causing COVID-19 are a major risk to public health worldwide due to the potential for phenotypic change and increases in pathogenicity, transmissibility and/or vaccine escape. Recognising signatures of new variants in terms of replacing growth and severity are key to informing the public health response. To assess this, we aimed to investigate key time periods in the course of infection, hospitalisation and death, by variant. We linked datasets on contact tracing (Contact Tracing Advisory Service), testing (the Second-Generation Surveillance System) and hospitalisation (the Admitted Patient Care dataset) for the entire length of contact tracing in the England – from March 2020 to March 2022. We modelled, for England, time delay distributions using a Bayesian doubly interval censored modelling approach for the SARS-CoV-2 variants Alpha, Delta, Delta Plus (AY.4.2), Omicron BA.1 and Omicron BA.2. This was conducted for the incubation period, the time from infection to hospitalisation and hospitalisation to death. We further modelled the growth of novel variant replacement using a generalised additive model with a negative binomial error structure and the relationship between incubation period length and the risk of a fatality using a Bernoulli generalised linear model with a logit link. The mean incubation periods for each variant were: Alpha 4.19 (95% credible interval (CrI) 4.13–4.26) days; Delta 3.87 (95% CrI 3.82–3.93) days; Delta Plus 3.92 (95% CrI 3.87–3.98) days; Omicron BA.1 3.67 (95% CrI 3.61–3.72) days and Omicron BA.2 3.48 (95% CrI 3.43–3.53) days. The mean time from infection to hospitalisation was for Alpha 11.31 (95% CrI 11.20–11.41) days, Delta 10.36 (95% CrI 10.26–10.45) days and Omicron BA.1 11.54 (95% CrI 11.38–11.70) days. The mean time from hospitalisation to death was, for Alpha 14.31 (95% CrI 14.00–14.62) days; Delta 12.81 (95% CrI 12.62–13.00) days and Omicron BA.2 16.02 (95% CrI 15.46–16.60) days. The 95th percentile of the incubation periods were: Alpha 11.19 (95% CrI 10.92–11.48) days; Delta 9.97 (95% CrI 9.73–10.21) days; Delta Plus 9.99 (95% CrI 9.78–10.24) days; Omicron BA.1 9.45 (95% CrI 9.23–9.67) days and Omicron BA.2 8.83 (95% CrI 8.62–9.05) days. Shorter incubation periods were associated with greater fatality risk when adjusted for age, sex, variant, vaccination status, vaccination manufacturer and time since last dose with an odds ratio of 0.83 (95% confidence interval 0.82–0.83) (P value < 0.05). Variants of SARS-CoV-2 that have replaced previously dominant variants have had shorter incubation periods. Conversely co-existing variants have had very similar and non-distinct incubation period distributions. Shorter incubation periods reflect generation time advantage, with a reduction in the time to the peak infectious period, and may be a significant factor in novel variant replacing growth. Shorter times for admission to hospital and death were associated with variant severity – the most severe variant, Delta, led to significantly earlier hospitalisation, and death. These measures are likely important for future risk assessment of new variants, and their potential impact on population health.
Trial and Error: Lawyers and Nonlawyer Advocates
- Anna E. Carpenter, Alyx Mark, Colleen F. Shanahan
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- Journal:
- Law & Social Inquiry / Volume 42 / Issue 4 / Fall 2017
- Published online by Cambridge University Press:
- 27 December 2018, pp. 1023-1057
- Print publication:
- Fall 2017
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Nonlawyer advocates are one proposed solution to the access to justice crisis. Theory and research suggest that nonlawyers might be effective, yet scholars know very little, empirically, about nonlawyer practice in the United States. Using data from more than 5,000 unemployment insurance appeal hearings and interviews with lawyers and nonlawyers who represent employers in these hearings, this article explores how both types of representatives develop expertise and what this means for effectiveness. We find judges play a critical role in shaping nonlawyer legal expertise and nonlawyers develop expertise almost exclusively through “trial and error.” We find evidence that while experienced nonlawyers can help parties through their expertise with common court procedures and basic substantive legal concepts, they are not equipped to challenge judges on contested issues of substantive or procedural law in individual cases, advance novel legal claims, or advocate for law reform on a broader scale. These findings have implications for future access to justice research and interventions.