ABSTRACT
Reducing procedural discomfort for children requiring respiratory testing for SARS-CoV-2 is important in supporting testing strategies for case identification. Alternative sampling methods to nose and throat swabs, which can be self-collected, may reduce laboratory-based testing requirements and provide rapid results for clearance to attend school or hospital settings. The aim of this study was to compare preference and diagnostic sensitivity of a novel anterior nasal swab (ANS), and saliva, with a standard combined nose and throat (CTN) swab. The three samples were self-collected by children aged 5-18 years who had COVID-19 or were a household close contact. Samples were analysed by reverse transcription polymerase chain reaction (RT-PCR) on the Allplex SARS-CoV-2 Assay. Most children and parents preferred the ANS and saliva swab over the CTN swab for future testing. The ANS was highly sensitive (sensitivity 1.000 (95% Confidence Interval (CI) 0.920, 1.000)) for SARS-CoV-2 detection, compared to saliva (sensitivity 0.886, 95% CI 0.754, 0.962). We conclude the novel ANS is a highly sensitive and more comfortable method for SARS-CoV-2 detection when compared to CTN swab.
Subject(s)
COVID-19ABSTRACT
Background: Household studies are crucial for understanding the transmission of SARS-CoV-2 infection, which may be underestimated from PCR testing of respiratory samples alone. We aim to combine assessment of household mitigation measures; nasopharyngeal, saliva and stool PCR testing; along with mucosal and systemic SARS-CoV-2 specific antibodies, to comprehensively characterise SARS-CoV-2 infection and transmission in households. Methods: Between March and September 2020, we obtained samples from 92 participants in 26 households in Melbourne, Australia, in a 4-week period following onset of infection with ancestral SARS-CoV-2 variants. Results: The secondary attack rate was 36% (24/66) when using nasopharyngeal swab (NPS) PCR positivity alone. However, when respiratory and non-respiratory samples were combined with antibody responses in blood and saliva, the secondary attack rate was 76% (50/66). SARS-CoV-2 viral load of the index case and household isolation measures were key factors that determine secondary transmission. In 27% (7/26) of households, all family members tested positive by NPS for SARS-CoV-2 and were characterised by lower respiratory Ct-values than low transmission families (Median 22.62 vs 32.91; IQR 17.06 to 28.67 vs 30.37 to 34.24). High transmission families were associated with enhanced plasma antibody responses to multiple SARS-CoV-2 antigens and the presence of neutralising antibodies. Three distinguishing saliva SARS-CoV-2 antibody features were identified according to age (IgA1 to Spike 1, IgA1 to nucleocapsid protein (NP), suggesting that adults and children generate distinct mucosal antibody responses during the acute phase of infection. Conclusion: Utilising respiratory and non-respiratory PCR testing, along with measurement of SARS-CoV-2 specific local and systemic antibodies, provides a more accurate assessment of infection within households and highlights some of the immunological differences in response between children and adults.
Subject(s)
Mouth Diseases , Nasopharyngitis , COVID-19ABSTRACT
Children have lower hospitalisation and mortality rates for coronavirus disease-2019 (COVID-19) than adults; however, younger children (<4 years of age)1 may develop more severe disease than older children. To date, the immune correlates of severe COVID-19 in young children have been poorly characterized. We report the kinetics of immune responses in relation to clinical and virological features in an infant with acute severe COVID-19. Systemic cellular and cytokine profiling showed initial increase in neutrophils and monocytes with depletion of lymphoid cell populations (particularly CD8+ T and NK cells) and elevated inflammatory cytokines. Expansion of memory CD4+T (but not CD8+T) cells occurred over time, with predominant Th2 bias. Marked activation of T cell populations observed during the acute infection gradually resolved as the child recovered. Significant in vitro activation of T-cell populations and robust cytokine production, in response to inactivated SARS-CoV-2 stimulation, was observed 3 months after infection indicating durable, long-lived cellular immune memory.