Background:

The EuCARE project includes several cohorts of patients and schools to provide an advance
response to COVID-19 epidemics. The cohorts belong to different geographic areas
including European countries, Kenya, Mexico, Russia and Vietnam, and will consolidate or
expand interactions with other cohorts. A comprehensive multidisciplinary team of
clinicians, virologists, epidemiologists, statisticians and top experts in artificial
intelligence will collaborate to investigate:

- the natural and artificial immunity to the different viral variants in health care
workers;

- the clinical course and long-term follow up of hospitalized COVID-19 patients to
derive the role of different viral variants in the outcome of the infection,
including post COVID-19 condition;

- the best strategies to control the spread of different viral variants in schools, by
comparing the outcome of diverse containment and prevention measures in relation to
the prevalence and dynamics of the variants.

Post COVID-19 condition is defined as the persistence or new onset of symptoms 3 months
after an acute episode of COVID-19; these symptoms could last 2 or even more months and
are not explained by an alternative diagnosis. The prevalence of these ongoing symptoms
is very variable among the different studies, but seems high, affecting up to 50-60% of
recovered patients.

Moreover, the post COVID-19 condition is described more commonly in females and more
severe patients, but can be observed at all ages and in patients with a mild acute
episode of COVID-19 disease.

AIMS AND OBJECTIVES The hypothesis of the study is that a relatively high proportion of
patients recovered from an acute COVID-19 episode develops long-term sequelae, defined as
the presence of ongoing or new onset physical and/or psychological symptoms at three
months after the acute illness. These symptoms could last at least two months or even
longer.

The mechanisms underpinning the post-acute and chronic manifestations of COVID-19 are not
entirely understood.

The predictors of post COVID-19 condition have not yet identified, but the first evidence
suggest that patients experiencing persistent symptoms, at 4-weeks or 8-weeks after the
acute disease, were more likely elderly, females and hospitalized in the acute phase
compared to the patients reporting symptoms for a short period of time (Carole et al,
2021).

We also hypothesized that older age, female gender, severity of disease and previous
patients' comorbidities could be risk factors for the development of post COVID-19
condition.

Finally, our hypothesis is that the new variant "Omicron" could be associated with a
lower inflammation and disease's severity during the acute phase and, thus, with a lower
incidence of post COVID-19 condition.

Study objective:

Primary objective is to assess the incidence and risk factors of post COVID-19 condition
in a cohort of recovered COVID-19 patients.

Secondary objectives are:

to evaluate the association between circulating SARS-CoV-2 variants and risk of post
COVID-19 condition; to evaluate long-term residual organ damage (lung, hearth, Central
Nervous System, CNS, Peripheral Nervous System, PNS) in relation to patient's
characteristics and virology (variant, viral load in the acute phase).