Influence of Military Preventive Policy for reCruit Training on COVID-19 Seroconversion

Overview

This study is intended to address the association between vitamin D status and seroconversion to SARS-CoV-2 in healthy young adults. The primary aim of the study is to determine the rates of 'silent' seroconversion rates, consistent with asymptomatic transmission of SARS-CoV-2, in a young healthy adult population with a wide spread of vitamin D concentrations. The secondary aims of this study are to explore: 1. Any effect of vitamin D status on symptomatic illness. 2. The background 'point' prevalence and subsequent rate of increase in seropositivity for SARS-CoV-2 in healthy young adults. 3. The individual reductions in seropositivity to SARS-CoV-2 over time, and changes in seropositivity in a defined young adult population over time. 4. Where salivary Immunoglobulin A (IgA) may be used to provide an alternative/ complementary serological method 5. The effect (if any) of vitamin D supplementation on seroconversion rates stratified by: i) level of baseline vitamin D 'deficiency/ insufficiency/ sufficiency' status; ii) extent of BMI-defined normal/overweight/obesity cut-offs and iii) gender.

The primary aim of the study is to determine the rates of 'silent' seroconversion rates, consistent with asymptomatic transmission of SARS-CoV-2, in a young healthy adult population with a wide spread of vitamin D concentrations. The study will be conducted over 16 weeks in two populations: Service Personnel undertaking initial military training, who are supplementing with vitamin D (1000 IU/day D3 for 4 weeks, and 400 IU/d D3 as a maintenance dose), and civilian students who are not supplementing. We will recruit adults aged 18-30 years old. Military and civilian participants will be recruited respectively in Catterick and Leeds, UK to start in coincidence with the recommencement of Autumn semester. In accordance with our power calculation and anticipated drop-out rate, 450 volunteers will be recruited in each group. Data collected at baseline and after 5, 9, 12 and 16 weeks will include seroconversion status assessed from a validated Dried Blood Spot (DBS) method in conjunction with novel salivary antibody testing, plus structured questionnaire responses screening for Covid-19 symptoms. Physical and demographic characteristics and serum levels of vitamin D concentrations collected from participants at study entry will facilitate secondary aims in relation to exploring the influence of gender, ethnicity, body mass and body mass index (BMI) on asymptomatic seroconversion, as well as interactions with vitamin D status and supplementation.