Who Is Immune Against COVID-19 and Safe to Return to Work: The Impact of Laboratory Assays

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 2019 (COVID-19) as a pandemic infectious disease which has led to thousands of deaths around the world. The Coronaviridae family is the second cause of the common cold that targets human respiratory tracts. Specific diagnostic laboratory tests in addition to clinical investigations would be helpful in confirming COVID-19 in the early stages for controlling the disease. Upon SARS-CoV-2 infection, antibody responses are produced during the early phase of illness (>7 days), meanwhile, viral nucleic acid real-time reverse-transcription polymerase chain reaction (rRT-PCR) test is applied as the confirmatory assay in the first 5-6 days after the onset of illness. Due to the rise of antibodies, the viral nucleic acid represents a gradual decline. These laboratory tests may be considered valuable for monitoring the patient’s status to prevent the spreading of infections and keep him/her in quarantine. The results of molecular and serological assays revealed that whether the person is recovered and protected against disease. Furthermore, regarding the rise of antibody titer and undetectable viral RNA, it may be possible to make a decision about when the recovered people could back to work and social life.