Retarded decline of the share of SARS-CoV-2-positive children in North Rhine-Westphalia, Germany

Abstract

Knowledge on the mechanisms of viral spread, of time-related changes, and age-specific factors of severe acute respiratory syndrome coronavirus 2 infections is important to develop recommendations aimed at controlling the pandemic. In this context, longitudinal data on proportions of positive results in different age groups are rare. Data on total positive counts and on shares of positive counts deriving from a private (MVZ) and a University (RWTH) laboratory were analyzed retrospectively and compared with public data on total positive counts of the Robert Koch Institute (RKI). Data were covered for Weeks 9-24 of the year 2020 and all patient ages. Total positive counts were lower in children compared to adults. Proportions of children and adults tested positive were 3%-5% and 5%-7%, respectively. RKI and MVZ data showed similar time-related patterns. Patients of 20-60 years of age did account for the initial virus spread (maximum infection rates at Weeks 9-11). Thereafter, infection rates decreased in older patients whereas children did not show a comparable time-related decrease. Pediatric data generated in outpatient settings and hospitals differed markedly which should be considered in further studies. In summary, compared with adults children are less affected by severe acute respiratory syndrome coronavirus 2 infections and are unlikely to account for the initial viral spread. However, children show sustained viral activity and may serve as a viral reservoir.

Keywords: COVID-2019; SARS-CoV-2; children; epidemiology; viral reservoir; virus spread.

Figure 1

(A) (MVZ data) Mean absolute numbers of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) tests among pediatric age groups (age 0–14 years) and older age groups (age ≥15 years) studied in 1‐year intervals. With exception from Weeks 9 and 10, SARS‐CoV‐2 testing was performed less frequently in younger age groups. From Week 19, the testing rates increased in children and decreased among older patients without reaching similar levels. (B) (MVZ data) Mean numbers of weekly SARS‐CoV‐2 studies. Investigations at different ages between Weeks 9 and 24. Lowest rates of SARS‐CoV‐2 tests were observed among children and very old patients with a maximum of tests in patients of about 50–60 years of age. (C) (MVZ data) Absolute counts of positive test results between Weeks 9–24 for different age groups. Adults (≥20 years): thin solid line, mean of absolute counts of positive tests calculated over all 5‐year‐age groups. Children: absolute counts of positive tests for age group 0–4 years (thick solid line), age group 5–9 years (thick dashed line), age group 10–14 years (thick dotted line), and age group 15–19 years (thin dashed line). The number of children tested positive was considerably lower with highest numbers after Week 18 in age groups 0–14 years

Figure 2

(A) (MVZ data) Normalized absolute counts of positive test results of MVZ data. Analyses performed between Weeks 9 and 24 for different age groups (n = 5,579) (MVZ cohort). Adult patients in 5‐year intervals: thin dotted lines. Pediatric age groups: age 0–4: thick solid line; age 5–9: thick dashed line; age 10–14: thick dotted line. Maximum counts of patients newly diagnosed positive for SARS‐CoV‐2 infection (100%) were recorded in Weeks 12–15 for all adult age groups. During the same time, a first peak was also found among children aged 0–14 years who not only failed to show decreasing numbers during the following time but also experienced their maximum peak during Weeks 19–21. (B) (RKI data) Normalized absolute counts of positive test results of RKI data. Data collected during the Weeks 9–24 for different age groups (n = 188,133). Similar to the MVZ data, all age groups of the RKI data showed the highest absolute numbers of positive findings (100%) in Weeks 13–14. Thereafter, in all adult groups (thin pointed lines; 5‐year intervals) numbers of newly infected patients decreased to below 20% of the maximum numbers until Week 24. In children up to 14 years of age, in contrast, no comparable decrease of newly diagnosed patients was recorded (age 0–4: thick solid line; age 5–9: thick dashed line; age 10–14: thick dotted line). SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2

Figure 3

(A) (MVZ data) Normalized shares of positive results from MVZ data. Calculations performed for different 5‐year age intervals, distinguishing between different weeks. Normalization performed for the week with the highest share of positive findings (100%). Most middle‐aged age groups (age 15–44 years) showed their highest rates of positive findings at Week 9 (thin dotted lines), followed by most of the remaining adults (thin solid lines). Children between 5 and 14 years, in contrast, showed their peaks later and also showed a delayed decrease. Children: age 0–4: thick solid line; age 5–9: thick dashed line; age 10–14: thick dotted line. (B) (MVZ data) Patient age versus week of maximum share of positive SARS‐CoV‐2 findings. Calculations performed for 1‐year intervals. Closed circle: peak observed in one distinct week. Open circle: two peaks in two different weeks observed for the respective age group. Patients between 20 and 60 years of age showed maximum percentages of positive tests early during the pandemic (Weeks 9–11). In older patients maximum percentages of positive tests occurred between Weeks 11 and 15, whereas most children showed their peaks from Week 13 on. (C) (MVZ data) Cumulative change of share of positive test results in comparison to the preceding week depending on age. Whereas infection rates continuously decrease from 10 years of age, this is not the case between 0 and 9 years of age. SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2

Figure 4

(A) (MVZ + RWTH data) Comparison of test results in different settings among children of 0–14 years of age. Comparison of the share of positive findings in ambulatory (MVZ) and hospital (MVZ/RWTH) settings (normalized depiction). Only studies among children performed in ambulatory settings showed a similar result pattern as on overall analysis (dashed line) whereas only sporadic positive cases were detected in hospitals. (B) (MVZ + RWTH data) Comparison of test results in different settings among patients from 15 years of age. Comparison of the share of positive findings in ambulatory (MVZ) and hospital (MVZ, RWTH) settings (normalized depiction). Irrespective from the site of analysis similar result patterns over time were observed. RWTH, RWTH Aachen University Hospital