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].