Clinical immunity in discharged medical patients with COVID-19

Most studies on SARS-CoV-2 infection show that people who have recovered from COVID-19 have antibodies to the virus. No study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to the infection relapse but however, to date, no human reinfections with SARS-CoV-2 have been confirmed.

In our prospective, multicenter, cohort study we investigated within three months all patients, with confirmed COVID-19, discharged from two Hospitals (Legnano and Magenta Hospitals), in an area of Italy severely affected by the infection. Telephone follow-up at 1 and 2 months and clinical contact within 3 months was initiated; demographic, clinical, radiologic and laboratory data were recorded in electronic medical records and updated.

Of 1081 patients involved, 804 (74.3%) were discharged alive. For all these patients we obtained follow-up data. At 1 and 2 months none has died and none has had any signs of recurrence of infectious at both telephone interview and clinical visit.

Our clinical observation have confirmed two basic points: the reinfection is very unlikely and any antibody immunity protects against recurrence, at least in the short term.