Data_Sheet_2_Sero-Surveillance to Monitor the Trend of SARS-CoV-2 Infection Transmission in India: Study Protocol for a Multi Site, Community Based Longitudinal Cohort Study.pdf

IntroductionLarge-scale sero-prevalence studies with representation from all age groups are required to estimate the true burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in the community. Serial serological surveys in fixed cohorts enable study of dynamics of viral transmission and correlates of immune response over time in the context of gradual introduction of COVID-19 vaccines and repeated upsurge of cases during the pandemic.
MethodsThis longitudinal study will involve follow-up of a cohort of 25,000 individuals (5,000 per site) aged 2 years and above recruited from five existing demographic surveillance sites in India. The cohort will be tested for the presence of IgG antibodies against S1/S2 spike protein subunits of SARS-CoV-2 in four rounds; once at baseline and subsequently, at intervals of 4 months for a year between January 2021 and January 2022. Neutralization assays will be carried out in a subset of seropositive samples in each round to quantify the antibody response and to estimate the durability of antibody response. Serial serological surveys will be complemented by fortnightly phone based syndromic surveillance to assess the burden of symptomatic acute febrile illness/ influenza like illness in the same cohort. A bio-repository will also be established to store the serum samples collected in all rounds of serological surveys.
DiscussionThe population based sero-epidemiological studies will help to determine the burden of COVID-19 at the community level in urban and rural Indian populations and guide in monitoring the trends in the transmission of SARS-CoV-2 infection. Risk factors for infection will be identified to inform future control strategies. The serial serological surveys in the same set of participants will help determine the viral transmission dynamics and durability of neutralizing immune response in participants with or without symptomatic COVID infection.

引言
为精准评估社区内严重急性呼吸综合征冠状病毒2（SARS-CoV-2）感染的实际疾病负担，需开展覆盖全年龄段人群的大规模血清流行率（sero-prevalence）研究。在新冠疫苗逐步推广、疫情期间病例反复反弹的背景下，固定队列（cohort）的系列血清学调查（serial serological surveys）可用于研究病毒传播动态以及随时间变化的免疫应答相关因素。
方法
本项纵向研究将对从印度5个现有人口监测点招募的25000名2岁及以上个体（每个监测点5000人）队列进行随访。该队列将开展4轮针对SARS-CoV-2 S1/S2刺突蛋白（spike protein）亚基的免疫球蛋白G（IgG）抗体检测：基线检测1次，随后于2021年1月至2022年1月的1年内，每4个月检测1次。每一轮检测中，将对部分血清学阳性（seropositive）样本开展中和试验（neutralization assays），以量化抗体应答水平并评估抗体应答的持久性。系列血清学调查将辅以每两周1次的电话症状监测，以评估该队列中症状性急性发热性疾病/流感样病例的疾病负担。本研究还将建立生物样本库（bio-repository），用于保存所有血清学调查轮次采集的血清样本。
讨论
本项基于人群的血清流行病学（sero-epidemiological）研究，可明确印度城乡社区人群的新冠疾病负担，并为监测SARS-CoV-2感染的传播趋势提供指导。研究将明确感染的危险因素，为后续防控策略制定提供依据。对同一批受试者开展的系列血清学调查，可明确有症状或无症状新冠感染者的病毒传播动态以及中和免疫应答（neutralizing immune response）的持久性。