Neutralizing Antibody Levels as a Correlate of Protection Against SARS-CoV-2 Infection: A Modeling Analysis.

Although anti-severe acute respiratory syndrome-coronavirus 2 antibody kinetics have been described in large populations of vaccinated individuals, we still poorly understand how they evolve during a natural infection and how this impacts viral clearance. For that purpose, we analyzed the kinetics of both viral load and neutralizing antibody levels in a prospective cohort of individuals during acute infection with alpha variant. Using a mathematical model, we show that the progressive increase in neutralizing antibodies leads to a shortening of the half-life of both infected cells and infectious viral particles. We estimated that the neutralizing activity reached 90% of its maximal level within 11 days after symptom onset and could reduce the half-life of both infected cells and circulating virus by a 6-fold factor, thus playing a key role to achieve rapid viral clearance. Using this model, we conducted a simulation study to predict in a more general context the protection conferred by pre-existing neutralization titers, due to either vaccination or prior infection. We predicted that a neutralizing activity, as measured by 50% effective dose > 103 , could reduce by 46% the risk of having viral load detectable by standard polymerase chain reaction assays and by 98% the risk of having viral load above the threshold of infectiousness. Our model shows that neutralizing activity could be used to define correlates of protection against infection and transmission.

Psychosocial risk factors for increased emergency hospital utilization by sickle cell disease patients: a systematic review protocol.

OBJECTIVE: To assess psychosocial risk factors for increased emergency hospital utilization by sickle cell patients. INTRODUCTION: Emergency hospital utilization by sickle cell disease patients is high but heterogeneous between patients and in a given patient over time. Psychosocial factors affect emergency hospital utilization and are a possible target to improve the management of sickle cell disease. INCLUSION CRITERIA: This review will include all original quantitative studies evaluating the impact of psychosocial risk factors on emergency hospital utilization by sickle cell disease patients. There will be no language restriction. METHODS: PubMed, Embase, CINAHL, PubPsych, LiSSa, and Web of Science will be searched using a peer-reviewed search strategy. Study selection and extraction of data will be performed independently by two authors. Discrepancies will be solved by consensus or, if needed, by a third author. The authors will assess study quality, as well as perform a narrative synthesis of included studies, and where possible, meta-analyses with evaluation of heterogeneity and publication bias. SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO CRD42019140435.