The aim of the SARS-CoV-2-CZ-PREVAL-II Study is to quantify the prevalence of participants with antibodies against SARS-CoV-2 and/or cell immunity against SARS-CoV-2 in four specific cohorts: participants with chronic illness, healthy volunteers participating in the Study of the Czech Academy of Science, healthcare workers, and healthy volunteers that participated in the "Herd Immunity Study SARS-CoV-2-CZ-Preval" in May 2020.
The primary aim of the study is to estimate the number of people with anti-SARS-CoV-2-antibodies, i.e., people with COVID-19 history, or with vaccination against COVID-19.
Antibodies test will focus on two main proteins of virus SARS-CoV-2: S-protein and N-protein.
The secondary aims of the study are:
* quantitative analysis of cellular immunity and the other relevant markers,
* estimation of the proportion of participants with asymptomatic COVID-19 infection
* quantification of anti-SARS-CoV-2 antibodies and cell immunity according to individual risk factors.
