A mathematical model of SARS-CoV-2 immunity predicts paxlovid rebound.

Nirmatrelvir/ritonavir (Paxlovid), an oral antiviral medication targeting SARS-CoV-2, remains an important treatment for COVID-19. Initial studies of nirmatrelvir/ritonavir were performed in SARS-CoV-2 unvaccinated patients without prior confirmed SARS-CoV-2 infection; however, most individuals have now either been vaccinated and/or have experienced SARS-CoV-2 infection. After nirmatrelvir/ritonavir became widely available, reports surfaced of "Paxlovid rebound," a phenomenon in which symptoms (and SARS-CoV-2 test positivity) would initially resolve, but after finishing treatment, symptoms and test positivity would return. We used a previously described parsimonious mathematical model of immunity to SARS-CoV-2 infection to model the effect of nirmatrelvir/ritonavir treatment in unvaccinated and vaccinated patients. Model simulations show that viral rebound after treatment occurs only in vaccinated patients, while unvaccinated (SARS-COV-2 naïve) patients treated with nirmatrelvir/ritonavir do not experience any rebound in viral load. This work suggests that an approach combining parsimonious models of the immune system could be used to gain important insights in the context of emerging pathogens.

Clinical characteristics of pediatric SARS-CoV-2 infection and coronavirus disease 2019 (COVID-19) in Kuwait.

Clinical presentation of coronavirus disease-2019 (COVID-19) ranges from asymptomatic to severe and life-threatening. National-level registries found that children, generally, have less severe disease when compared with adults. However, most asymptomatically infected children will not present to hospital and may be missed. We aimed to describe the clinical characteristics in pediatric COVID-19 patients in Kuwait, and to estimate the potential duration of viral shedding. A retrospective cohort study was performed in Jaber Alahmad Hospital (JAH) from February 29 to April 30, 2020. During the study period and as part of the public health measures, all severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients from 1 month to 18 years old, regardless of symptoms, were hospitalized at JAH, and were included. Polymerase chain reaction (PCR) negativity was defined as having two consecutive negative PCR results from a respiratory specimen. Descriptive statistics and multivariable regression analyses were performed. We found that 67.9% (95% CI, 59.4%-75.3%) of 134 SARS-CoV-2-infected children were asymptomatic. Median PCR positivity was 15 days and did not vary with symptoms. Among patients who had laboratory investigations and chest imaging, symptomatic infection was associated with elevated C-reactive protein and procalcitonin, and radiographic pneumonia. Asymptomatic SARS-CoV-2 infection is very common in children. Among symptomatic patients, the disease seems to be mild. Children exhibit substantial duration of viral shedding, regardless of symptoms.