Epidemiological and clinical features of Croatian children and adolescents with a PCR-confirmed coronavirus disease 2019: differences between the first and second epidemic wave.

Aim: To describe epidemiological and clinical features of Croatian children and adolescents with a polymerase chain reaction (PCR)-confirmed coronavirus disease 2019. ----- Methods: Data on patients aged ≤19 years with a positive SARS-CoV-2 PCR test recorded in the period March 12-May 12 (first wave) and June 19-July 19, 2020 (second wave) were retrospectively analyzed. The periods were separated by several weeks with no incident cases. ----- Results: We analyzed data on 289 children and adolescents (6.5% of all cases; incidence rate [IR]=3.54, 95% confidence interval [CI] 3.14-3.97/million person-days), 124 in the first wave (IR=2.27) and 165 in the second wave (IR=6.37): IRR second/first=2.71 (2.13-3.44). During the first wave, the incidence was highest in infants (IR=3.48), while during the second wave it progressively increased to IR = 7.37 in 15-19-year olds. Family members were the key epidemiological contacts (72.6% cases), particularly during the first wave (95.8% vs 56.3%). Overall, 41.3% patients were asymptomatic, 25.3% in the first and 52.6% in the second wave. Age 15-19 years (vs younger) was associated with a higher (RR = 1.26, 1.02-1.54) and infection in the second wave with a lower probability (RR=0.66, 0.53-0.81) of being symptomatic. The most common symptoms were fever, cough, and rhinorrhea. In children aged ≥7 years, headache, anosmia/ageusia, and sore throat were also recorded. Only one child suffered a severe disease. All but 18 (7.8%) children were treated only symptomatically, and all fully recovered. ----- Conclusion: A large proportion of SARS-CoV-2 PCR-positive children/adolescents were asymptomatic. The associated disease was predominantly mild, comparably so in the first and second pandemic wave.