Discussion:
In our study evaluating SARS-CoV-2 viral persistence in ICC, we found
that the median time to the first of two negative tests was 6 weeks.
Most children were tested in outpatient settings prior to admission or
for procedural sedation, and over half of those tested were asymptomatic
at the time of their first positive test. There was no significant
difference in time to negativity among symptomatic versus asymptomatic
children. Among children who remained positive at day 30, half had
CT values <30, suggesting persistence
of moderate to high viral loads and assumed potential risk of
transmission. Our study highlights the importance of PCR-based screening
for ICC to guide isolation duration, irrespective of symptom
presentation. These data support our current practice, with the need for
at least two negative tests, given the potential for intermittent
negative followed by positive results, and risk for ongoing, potential
transmission even several weeks from initial infection.
The CDC recommends an isolation period of 10 days in healthy,
non-immunocompromised individuals with SARS-CoV-2 infection based on
studies that demonstrate the absence of viable/transmissible virus
beyond this period.16 Immunocompromised patients can
have a longer period of infectivity, but there is little available
evidence in the literature to guide infection control practices. Our
study revealed a prolonged period of viral persistence in ICC, with a
longer period of positivity compared with a case series of ICC and a
study of immunocompromised adults.9,17 Children with
leukemia/lymphoma had longer viral persistence compared with children
with other immunocompromising conditions, which we hypothesize is due to
this population having the highest impairment of adaptive immunity.
These children also represent the population of children with the
greatest degree of lymphopenia, which has been shown in adults to be
associated with more severe disease.18 Another study
has also shown that patients critically ill from SARS-CoV-2 were more
likely to have a decrease in CD3+CD4+ T-cells compared to non-critical
patients.19 Additionally, a study of adult cancer
patients found a general lack of T-cell response to CoV N, M and S
proteins from SARS-CoV-2. While these findings suggested a lack of a
protective T-cell response, the patients presented with mild illnesses
despite relatively high viral loads.12 And although we
had one death in our patient cohort post-bone marrow transplant,
allogeneic, autologous and CAR-T therapy patients have overall favorable
outcomes following SARS-CoV-2 infection.13
Similar to findings from adult studies, we did not see a relationship
between clinical presentation and persistent positive SARS-CoV-2 status.
An adult study of 3758 adults re-tested following initial SARS-CoV-2
infection found longer time to negativity to be associated with older
age, multiple comorbidities and solid organ transplant but not by degree
of immunocompromise or illness severity17. Our
findings serve as a reminder that even asymptomatic children may have
potentially transmissible virus several weeks after initial detection.
Asymptomatic ICC are a potentially important group that pose high risk
of transmissibility given their silent infection and prolonged
infectious period.
While PCR is unable to differentiate actively replicating virus from
viral shedding, CT values may serve as a useful
surrogate for viral load and potential transmissibility. Other studies
suggest that CT values of 25-30 represent moderate to
high viral loads. We evaluated CT values using the same
PCR assay for a small sample of patients with available clinical
samples, which demonstrated that half still had a moderately high viral
load even 3-4 weeks from their initial viral infection, regardless of
their presentation. Other studies evaluating samples with PCR, viral
culture, and subgenomic RNA have shown that CT values
similar to those found in our study were associated with viable,
culturable virus, as well as the presence of subgenomic RNA, which
indicates actively replicating virus.20 These data
further support the need for extended isolation duration for ICC given
the persistence of relatively low CT values, suggesting
potentially transmissible virus. Low CT values indicating relatively
high viral loads were observed even in asymptomatic ICC, reflecting a
need for test-based isolation protocols, rather than symptom-based
isolation.
There are several limitations of this single-center,
retrospective study. A small sample size precluded adjusted analyses to
account for factors that may influence viral persistence and increased
the risk of a type II error. Given the retrospective nature of the
study, there was non-standardized repeat testing, and the frequency and
intervals were not consistent between study participants. Repeat testing
at our institution was recommended at 3 weeks from the first positive
test, which may have increased our median time to negative testing, but
most children in our cohort were still positive at this timepoint. We
did not have a cohort of non-ICC with repeat SARS-CoV-2 testing, so we
were not able to compare the degree of viral persistence in ICC with a
healthy population. Finally, clinical SARS-\sout CoV-2 testing
was conducted on different testing platforms, and there were a limited
number of remaining sequential samples available for repeat testing to
yield CT data.
In conclusion, our study demonstrates prolonged viral persistence of
SARS-CoV-2 viral material in ICC, even in asymptomatic children, with
moderate to high viral loads seen in the majority of children several
weeks from initial positive testing. These findings highlight the
importance of PCR-based screening for ICC to help guide isolation
duration, irrespective of symptom presentation, given the risk for
ongoing transmission even several weeks from initial infection.
Conflicts of Interest: Suchitra Rao and Samuel R. Dominguez
received research support from BioFire Diagnostics; all other authors
have no conflicts of interest to disclose.
Acknowledgements: We would like to acknowledge the Clinical
Microbiology Laboratory at Children’s Hospital Colorado for their
tireless work during the pandemic.