Case 1
The first case is a 41-year-old Hispanic-Latina female pediatrician with no known chronic medical conditions who developed respiratory symptoms, fever, headaches, fatigue, anosmia and ageusia in March 2020 in the setting of a household exposure (her husband) who tested positive for SARS-CoV-2 2 days before her. Three days after her symptom onset, her nasopharyngeal (NP) swab sample was positive for SARS-CoV-2 by RT-PCR. Besides a persistent loss of smell and taste, her symptoms resolved without hospitalization or treatment. She was enrolled in an observational study and underwent serial NP swab sampling 7 times from April to September 2020, with negative quantitative RT-PCR results each time. In September, she developed respiratory symptoms and chest tightness and was again found to be positive for SARS-Co-V-2 by RT-PCR, which was further confirmed by quantitative RT-PCR testing (viral load (VL) 22,800 copies/mL). Similar to her first episode, she recovered without hospitalization or treatment. Her husband was also enrolled in the observational study and had nasopharyngeal and serum samples drawn at similar time points. However, the husband never re-tested positive for SARS-CoV-2 or had symptoms after his initial episode in March. The period between the patient’s first and second episodes was 174 days. Qualitative IgM and quantitative IgG was measured in samples obtained from April to October 2020 for both the patient and her husband (Figure 1 ) (see supplemental materials for detailed methods). In April, four weeks after her initial positive SARS-CoV-2 test, low but detectable levels of anti-Spike IgM and IgG were present in her serum Her IgG level peaked at 123 arbitrary units (AU)/mL in April and declined persistently thereafter (IgM>1.0 and IgG >50 AU/mL are considered positive). In September, during her second COVID-19 episode, she no longer had detectable levels of IgM, and her IgG level had dropped below 50 AU/mL. In contrast, the husband had detectable levels of IgM and IgG from April to October, and his levels of IgG peaked at 919.7 AU/mL in April and remained over 182 AU/mL through October. With this patient’s lack of comorbidities or evidence of prior infections, it is unclear why her antibody response was less robust and quicker to decline, although this may explain part of her susceptibility to reinfection. While available studies suggest that total anti-SARS-CoV-2 Ig is a reasonable correlate of protection, the literature and these cases also suggest that the presence of antibodies alone does not necessarily indicate protection from reinfection [13].