Illness characteristics of COVID-19 in children infected with the SARS-CoV-2 Delta variant (preprint)

ABSTRACT

Background The Delta (B.1.617.2) SARSCoV2 variant became the predominant UK circulating strain in May 2021. Whether COVID19 from Delta infection differs to infection with other variants in children is unknown. Methods Through the prospective COVID Symptom Study, 109,626 UK school-aged children were proxy-reported between December 28, 2020 and July 8, 2021. We selected all symptomatic children who tested positive for SARS-CoV-2 and were proxy-reported at least weekly, within two timeframes December 28, 2020 to May 6, 2021 (Alpha (B.1.1.7) the main UK circulating variant); and May 26 to July 8, 2021 (Delta the main UK circulating variant). We assessed illness profiles (symptom prevalence, duration, and burden), hospital presentation, and presence of long (>28 day) illness; and calculated odds ratios for symptoms presenting within the first 28 days of illness. Findings 694 (276 younger [5 11 years], 418 older [12 17 years]) symptomatic children tested positive for SARS-CoV-2 with Alpha infection and 706 (227 younger and 479 older) children with Delta infection. Median illness duration was short with either variant (overall cohort 5 days (IQR 2 9.75) with Alpha, 5 days (IQR 2 9) with Delta). The seven most prevalent symptoms were common to both variants. Symptom burden over the first 28 days was slightly greater with Delta compared with Alpha infection (in younger children, 3 (IQR 2 5) with Alpha, 4 (IQR 2 7) with Delta; in older children 5 (IQR 3 8) with Alpha and 6 (IQR 3 9) with Delta infection in older children). The odds of several symptoms were higher with Delta than Alpha infection, including headache and fever. Few children presented to hospital, and long illness duration was uncommon, with either variant. Interpretation COVID-19 in UK school-aged children due to SARSCoV2 Delta strain B.1.617.2 resembles illness due to the Alpha variant B.1.1.7., with short duration and similar symptom burden.