A prospective, longitudinal cohort study designed to follow-up on 500 Swiss military personnel who tested in 2020 for SARS-CoV-2 (regardless of whether positive or negative, but with a known test result). Participants are invited to undergo an intensive test battery to evaluate if they suffer COVID-19 sequelae. The testing will include evaluation of several body systems (cardio-vascular, pulmonary, neurological, ophthalmological, psychological and general) and male fertility in a voluntary subgroup. Immune markers and SARS-CoV-2 reinfection rates will also be evaluated. The study hypothesis is that SARS-CoV-2 infection causes a multi-system disease with sequelae detectable in a significant proportion of army recruits after infection with SARS-CoV-2.

During the COVID-19 pandemic, many members of the Swiss armed forces (SAF) contracted SARS-CoV-2. Up to one fifth may suffer from long-term sequelae, or so-called "Long COVID". The "LoCoMo" study is a prospective, longitudinal cohort study designed to follow-up on 500 tested recruits who tested either positive or negative while serving in the SAF in early 2020.

The aim of this research project is to evaluate long-term sequelae that may have occurred in members of the armed forces. By following up on those army recruits who tested positive and who were either symptomatic or asymptomatic and comparing them with those who test negative; symptoms and sequelae of the infection and impact on life quality can be tracked. The acquired data will also provide insights into the duration of immunity (or lack thereof) after symptomatic and asymptomatic infection and the kinetics of antibody decline in those who test positive. Furthermore, the study allows to follow-up on those army recruits who have confirmed positive tests for SARS-CoV-2 and to compare them to those who were negative. The data collected with this extensive test battery allows for a follow-up on a wide range of symptoms, estimated rates of re-infection as well as long- term sequelae after infection, including impact on ophthalmological function, on life quality and activities and impact on male fertility.

The results of the study can also be extrapolated to health-care workers and other young adults who constitute the backbone of the workforce. Because the proposed test battery is very broad and comprehensive it may also detect hitherto unknown, long-term sequelae, which might provide insight in the pathophysiology and general understanding of consequences of SARS-CoV-2 infection which is the basis to develop strategies to mitigate the sequelae. This study will provide essential knowledge on the multi-organ impact of COVID-19 in young persons in Switzerland.

Inclusion Criteria:

• Army recruits and personnel who tested for SARS-CoV-2.
• Completion of a consent form.
• Willing to participate and to complete the testing day in Zürich.

Additional inclusion criteria solely for the voluntary spermiogram test:

• Male
• No known abnormality of the reproductive system (e.g. Klinefelter-Syndrome)

Exclusion Criteria:

• Unwilling to provide consent. Unable to attend the testing day in Zurich.
• A narrow-angle glaucoma or sensitivity to a component of the Tropicamide eye drops is not an exclusion criterion, but the eye examination will be performed without pharmacological mydriasis.

The project population is Swiss army recruits who were tested for SARS-CoV-2 in 2020 (regardless of whether they tested positive or negative, but with a known test result). The total number of participants is 500 stratified to 167 participants per infection status (symptomatic, asymptomatic or no evidence of infection).