Patients with coronavirus disease‐2019 may be discharged based on clinical resolution of symptoms, and evidence for viral RNA clearance from the upper respiratory tract. Understanding the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) viral clearance profile is crucial to establish a re‐testing plan on discharge and ending isolation of patients. We aimed to evaluate the number of days that a patient needed to achieve undetectable levels of SARS‐CoV‐2 in upper respiratory tract specimens (nasopharyngeal swab and/or an oropharyngeal swab). The clearance and persistence of viral RNA was evaluated in two groups of positive patients: those who achieved two negative reverse transcription‐polymerase chain reaction (RT‐PCR) tests and those who kept testing positive. Patients were organized thereafter in two subgroups, mild illness patients discharged home and inpatients who had moderate to severe illness. Results from RT‐PCR tests were then correlated with results from the evaluation of the immune response. The study evidenced that most patients tested positive for more than 2 weeks and that persistence of viral RNA is not necessarily associated with severe disease but may result from a weaker immune response instead.

Background The SARS-CoV-2 pandemic was responsible for the death of millions of people around the world, which accelerated the study of vaccines. The BTN161b2 mRNA COVID-19 is a messenger RNA vaccine that encodes the spike protein of the virus. However, the duration of the protection conferred by this vaccine and factors associated with immune responses require validation in large cohorts. Methods Here, we present data of humoral immune response to vaccination in 4264 healthcare workers, tested before (T0) and 15 and 90 days (T1 and T2, respectively) following vaccination. Peripheral blood was collected for immunological analysis using the Quant SARS-CoV-2 IgG II Chemiluminescent Microparticle Immunoassay (CMIA) to determine anti-spike IgG, receptor binding domain (RBD), S1 subunit of SARS-CoV-2. Findings At T0, 96·8% (n=4129) of participants had IgG antibodies non-reactive to anti-SARS-CoV-2. Fifteen days after completing the vaccination, the IgG overall median titer was significantly elevated (21·7x10 3 AU/mL). Both for uni- and multivariate logistic regression analyses women presented higher antibody levels than men, independent of age. Titers were significantly altered among age groups, decreasing by each increase in 10-year of age. At 3 months after completing the vaccination, anti-SARS-CoV-2 IgG titers were 6·3-fold diminished. This real-world post-vaccination data confirmed production of a frequent and elevated anti-SARS-CoV-2 IgG titers, associated with high protection rates. Females and younger participants had higher titer 15 days after vaccination, and despite the significant reduction from 15-to-90 days, those with higher pre-vaccination titers maintained higher levels throughout the remaining timepoints. Interpretation These findings support the need to track humoral immunity kinetics to uncover viral susceptibility and eventually implement re-vaccination, particularly in groups prone to lower humoral immune response. Funding No external funding was received to conduct this study.

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Vaccination is a promising strategy to control the ongoing pandemic; however, solid organ recipients tend to develop a weaker immune response to vaccination. Anti-spike SARS-CoV-2 antibodies titers were measured 2-4 weeks post-vaccination completion in 131 KT patients without previous infection. Demographic, clinical, and laboratorial parameters were analyzed to identify which factors contributed to seroconversion. Factors that influenced seroconversion, that occurred in 76 patients (58%), were longer time post-transplant, immunosuppression without an antiproliferative drug and vaccination with mRNA vaccines. Patients who received mRNA vaccines had significantly higher rates of seroconversion compared with adenovirus vector vaccines (67% vs 33%, P < .001) and higher anti-spike IgG titers.These findings reinforce the need to discuss the vaccination strategy in this population, including a third dose with a mRNA vaccine.

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