Anna Nicholson-Little

Introduction Recruitment and training is vital to maintaining the size, deployability and effectiveness of armed forces, but was threatened early in the COVID-19 pandemic. Reports suggested asymptomatic seroconversion driving SARS-CoV-2 transmission in young adults. Potential association between lower vitamin D status and increased infection risk was also highlighted. We aimed to prospectively determine seroconversion and test the hypothesis that this would vary with vitamin D supplementation in representative populations. Methods Two cohorts were recruited from Yorkshire, Northern England. Infantry recruits received daily oral vitamin D (1000 IU for four weeks, followed by 400 IU for the remaining 22 weeks of training) in institutional countermeasures to facilitate ongoing training/co-habitation. Controls were recruited from an un-supplemented University population, subject to social distancing and household restrictions. Venous blood samples (baseline and Week 16) were assayed for vitamin D and anti-SARS-CoV-2 spike glycoprotein antibodies, with additional serology (weeks 4, 9, 12) by dried blood spot. Impact of supplementation was analysed on an intention-to-treat basis in volunteers completing testing at all timepoints and remaining unvaccinated against SARS-CoV-2. Variation in seroconversion with vitamin D change was explored across, and modelled within, each population. Results In the military (n=333) and University (n=222) cohorts, seroconversion rates were 44.4% vs 25.7% (P=0.003). At week 16, military recruits showed higher vitamin D (60.5 ± 19.5 mmol.L-1 vs. 53.5 ± 22.4 mmol.L-1, p < 0.001), despite <50% supplementation adherence. A statistically significant (p=0.005) effect of negative change in vitamin D (%) on seroconversion in recruits (OR of 0.991 and 95% CI of 0.984-0.997) was not evidenced in the University cohort. Conclusion Among unvaccinated populations, SARS-CoV-2 infection of infantry recruits was not reduced by institutional countermeasures, versus civilians subject to national restrictions. Vitamin D supplementation improved serum levels, but implementation did not have a clinically meaningful impact on seroconversion during military training.

Background Detecting antibody responses following infection with SARS-CoV-2 is necessary for sero-epidemiological studies and assessing the role of specific antibodies in disease, but serum or plasma sampling is not always viable due to logistical challenges. Dried blood spot sampling (DBS) is a cheaper, simpler alternative and samples can be self-collected and returned by post, reducing risk for SARS-CoV-2 exposure from direct patient contact. The value of large-scale DBS sampling for the assessment of serological responses to SARS-CoV-2 has not been assessed in depth and provides a model for examining the logistics of using this approach to other infectious diseases. The ability to measure specific antigens is attractive for remote outbreak situations where testing may be limited or for patients who require sampling after remote consultation. Methods We compared the performance of SARS-CoV-2 anti-spike and anti-nucleocapsid antibody detection from DBS samples with matched serum collected by venepuncture in a large population of asymptomatic young adults (N = 1070) living and working in congregate settings (military recruits, N = 625); university students, N = 445). We also compared the effect of self-sampling (ssDBS) with investigator-collected samples (labDBS) on assay performance, and the quantitative measurement of total IgA, IgG and IgM between DBS eluates and serum. Results Baseline seropositivity for anti-spike IgGAM antibody was significantly higher among university students than military recruits. Strong correlations were observed between matched DBS and serum samples in both university students and recruits for the anti-spike IgGAM assay. Minimal differences were found in results by ssDBS and labDBS and serum by Bland Altman and Cohen kappa analyses. LabDBS achieved 82.0% sensitivity and 98.2% specificity and ssDBS samples 86.1% sensitivity and 96.7% specificity for detecting anti-spike IgGAM antibodies relative to serum samples. For anti-SARS-CoV-2 nucleocapsid IgG there was qualitatively 100% agreement between serum and DBS samples and weak correlation in ratio measurements. Strong correlations were observed between serum and DBS-derived total IgG, IgA, and IgM. Conclusions This is the largest validation of DBS against paired serum for SARS-CoV-2 specific antibody measurement and we have shown that DBS retains performance from prior smaller studies. There were no significant differences regarding DBS collection methods, suggesting that self-collected samples are a viable sampling collection method. These data offer confidence that DBS can be employed more widely as an alternative to classical serology.

ORAL PRESENTATION Purpose: To evaluate and compare the acute group and individual endogenous hormone responses to three resistance exercise workouts and two load carriage workouts. Understanding hormone responses specific to military settings may enhance training optimisation in the future. Methods: Eighteen resistance exercise-trained male civilians (age: 19 to 38 y, mean 24.9 y) completed five experimental workouts and a control condition in a randomised order; three resistance exercise workouts (cluster, hypertrophy, endurance), two load carriage (90-min constant pace [CO-LC] or 6 × 8-min intervals [IT-LC], both carrying a rucksack with 25% body mass) workouts, and a control condition (60-minutes of rest). Venous blood was drawn before, immediately post workout, and 30-min and 24-h post workout. Testosterone (T), free testosterone (fT), growth hormone (GH), dehydroepiandrosterone sulphate (DHEAS), androstenedione (ANST), and insulin-like growth factor 1 (IGF-1) concentrations were subsequently analysed via liquid chromatography-mass spectrometry. Group responses were evaluated using two-way ANOVA’s with Tukey’s post-hoc analysis. The standardised standard deviations of the pre-post change scores (SDIR) were calculated to identify the presence of individual responses (Hopkins, 2015). Results: Group responses were observed despite large individual variations. T concentrations increased in response to hypertrophy (p < 0.001) and CO-LC (p = 0.02) workouts; fT concentrations increased in response to CO-LC (p < 0.001) and decreased following the hypertrophy (p = 0.035) workout; ANST concentrations increased in response to CO-LC (p = 0.007); GH increased following hypertrophy (p = 0.004), endurance (p = 0.04), IT-LC (p < 0.001), and CO-LC (p < 0.001) workouts; IGF-1 increased in response to the endurance (p = 0.018) workout. The SDIR effect size thresholds of extremely large (T, GH, DHEAS) and very large (T, GH, DHEAS, ANST, IGF-1) were achieved, representing an individualised pattern of hormone production in response to the different resistance exercise and load carriage workouts. Conclusions: The presence of within-workout variations in the hormonal responses to all workout types suggests that the mean group responses may not reflect the response experienced by all participants, and that the hormonal anabolic response differs between individuals. The group responses and within-workout variation suggest that a wide panel of endogenous hormones should be measured to provide clarity on the anabolic response to different types of training stimuli at the individual level. Military Impact: The anabolic response to training type differs between individuals. This research provides support to further investigate whether training interventions based upon an individualised anabolic hormone response to acute exercise lead to improved physical outcomes. Funding for this research was provided by Dstl MOD. References: Hopkins W. J Appl Physiol, 118:1444–1446,2015; doi:10.1152/japplphysiol.00098.2015