COVID-19 in Children: Correlation Between Epidemiologic, Clinical Characteristics, and RT-qPCR Cycle Threshold Values.

BACKGROUND: Initially, the impact of SARS-CoV-2 infection on children was unknown. Standard COVID-19 diagnosis is confirmed using real-time qPCR. Cycle threshold (Ct) values of RT-qPCR are inversely proportional to viral load and the test indirectly quantifies viral RNA copy numbers. The objective of this study was to determine the correlation between epidemiology, clinical characteristics, severity of confirmed COVID-19 cases, and Ct values. METHODS: An observational, analytical, cross-sectional study. All children with COVID-19 under 18 years old admitted to the Ricardo Gutiérrez Children's Hospital between March 1, 2020, and February 28, 2021, were included. SARS-CoV-2 infection was confirmed using RT-qPCR. RESULTS: Median age of patients was 7 years. Ct values were estimated in 419 cases, median Ct value was 23.5 [interquartile range (IQR): 18.9-30.9]. Levels were significantly lower in symptomatic than asymptomatic patients (Ct: 22.1; IQR: 18.4-22.1), in children <2 years of age (Ct: 20.6; IQR: 17.3-27.3) and when sample collection was <4 days after symptom onset (Ct: 21.1; IQR: 18.1-27.5). In children >2 years of age, Ct values were significantly lower in symptomatic (Ct: 22.6; IQR: 18.7-29.3) than asymptomatic (Ct: 31.2; IQR: 24.5-33.3) patients. CONCLUSIONS: Children younger than 2 years with COVID-19 have lower values of Ct-as a proxy for higher viral load-than older children. Symptomatic children over 2 years of age had lower Ct values compared with asymptomatic children.

Impact of varicella vaccination in Argentina: Seroprevalence in children and adults in a pediatric hospital.

BACKGROUND: Varicella is the primary infection caused by varicella-zoster virus (VZV). In Argentina, the varicella vaccine was introduced in the National Immunization Programme in 2015 as a single dose scheduled at 15 months of age. OBJECTIVES: To estimate VZV seroprevalence in a healthy hospital based population before and after vaccine introduction to the NIP. MATERIAL Y METHODS: Cross-sectional, observational, analytic study. Healthy subjects 1-40 years of age were included between June and December 2019 and tested for VZV-antibodies. Results were compared to data from a similar prevaccination study. RESULTS: Out of 599 samples, 11 indeterminate results were excluded, 424 were positive; overall seroprevalence rate was 72.1% (95 %CI = 68,3-75,8%). No differences were observed between pre and post vaccination studies for overall prevalence or between age groups, except for vaccinated children aged 11-15 (p = 0,005). Rates increased in both periods in subjects aged 6 years or older. Primary vaccine failures were 21%; in subjects <5 years 83% seropositive cases had been vaccinated, in >5 year-olds >90% seropositive cases were associated with a history of infection (OR: 10,4; IC95%: 6,4-16,8; p < 0,001) or household contact (OR:4,8; IC95%: 3,1-7,6; p < 0,001). Vaccination protected against disease (OR: 0.25; 95 %CI: 0.09-0.68; p = 0.004). CONCLUSION: seroprevalence was high in all age groups except in unvaccinated 12 to 15-month infants. Seropositivity was due to vaccination in 15 months to 5 year-old children and to infection in older children.