Clinical risk factors for predicting anti-Sars-CoV-2 antibody immunoreactivity duration after mild COVID-19 infection

Introduction: coronavirus disease 2019 (COVID-19) is a complex multisystem disorder. It is not yet well known whether symptoms in the acute phase correlate with the duration of the immune response and the persistence of chronic symptoms. Objective: this study aimed to assess and monitor the clinical symptoms of COVID-19 and correlate them with the production of neutralizing antibodies. Methods: a cohort of 69 health workers at the University Hospital of the Federal University of Espírito Santo (HUCAM-UFES/EBSERH) diagnosed with SARS-CoV-2 infection confirmed via RT-PCR (Real-Time Reverse Transcription–Polymerase Chain Reaction) were evaluated from the onset of symptoms up to six months. SARS-CoV-2 IgG and IgM assays were used to detect the presence of IgG and IgM against the nucleocapsid protein of SARS-CoV-2 in serum samples. IgG and IgM antibody serology, pulmonary function via spirometry, and the clinical evolution of patients were performed at 15, 30, 45, 60, 90, and 180 days after the onset of COVID-19 symptoms. Results: sixty-nine health workers (age, 40 ± 10 years; 74% women) were evaluated for six months. All subjects showed mild to moderate COVID-19. The mean number of symptoms was 5.1 (± 2.3). The most common initial symptoms were muscle pain (77%), headache (75%), anosmia (70%), ageusia (64%), runny nose (59%), fever (52%), and coughing (52%). After 30 days, the patients had anosmia (18%), asthenia (18%), adynamia (14%), muscle pain (7%), and ageusia (7%). Regarding lung function, 9.25% presented with an obstructive pattern, and all recovered after six months. Of all analyzed participants, 18/69 (26%) did not have any reactive IgG or IgM values in any of the assessments. The IgG serology curve showed a peak, whereas IgM had the highest mean value on the 15th day. There was a progressive decrease and levels similar to those at baseline after 90 days, and 15/53 (28%) remained with reactive IgG after six months. Sore throat and shortness of breath were found to be independent risk factors, and patients with these symptoms were 5.9 times more likely to have reactive IgG on the 180th day. Patients with diarrhea were four times more likely to have reactive IgM. Conclusion: our findings showed that 26% of patients did not produce a humoral response post-mild COVID-19. Their antibody titers dropped significantly after 90 days, and only 28% maintained reactive IgG antibodies after six months. Sore throat and shortness of breath are predictors of a longer duration of the humoral immune response.