S monovette plasma

A structured questionnaire was utilized to collect data from each study participant at enrollment (visit 1, 2–4 weeks after administration of 2nd primary dose) and each follow-up visit, i.e. at 4 months (visit 2), 8 months (visit 3) and 12 months (visit 4) post second dose (Fig. 1). Collected data included socio-demographic information (age, sex, education, migration background, ethnicity, marital status, household structure, occupation, and income), influenza-or COVID-like symptoms or presence of confirmed COVID-19 cases currently and in the past 6-months; co-morbidities (e.g. diabetes, hypertension, stroke, heart diseases and asthma). The vaccination type and administration dates were recorded. Information on receipt of booster dose was also collected during the follow-up phase. Height and weight were collected using stadiometer (Seca 217, Hamburg, Germany) and digital weighing scale (Camry-EB9063, China), respectively. Venous blood was collected at each visit in Lithium-heparin coated tubes (S-Monovette Plasma, Sarstedt AG & Co. KG, Nümbrecht, Germany), plasma was separated upon centrifugation, aliquoted, and stored at -80 °C until use.