ABSTRACT
BackgroundDuring the first wave of the SARS- CoV-2 pandemic in England, children accounted for just 1% of confirmed infections, had a milder clinical course and had much lower mortality than adults, a pattern similar to other international settings. The proportion of children in the UK infected with SARS-CoV-2 was unknown, with children less likely to attend symptomatic testing and issues with the sensitivity of real time reverse transcription PCR of oral/nasal swabs.ObjectivesTo measure the seroprevalence of SARS-CoV-2 antibodies in children of healthcare workers in the UK and to characterise the antibody response to SARS-CoV-2 infection and longitudinal antibody kinetics of SARS-CoV-2 infection.MethodsMulticentre observational prospective cohort study designed to determine seroprevalence of antibodies to SARS-CoV-2 in healthy children and report on symptoms experienced. Children of healthcare workers were recruited from five UK centres and underwent phlebotomy at three time points, beginning 16 April. There were follow up plasma/serum collections at two and six months after the original collection. Serum and/or plasma were tested for SARS-CoV-2 antibodies.Results1042 potential participants were screened for inclusion, with 35 excluded. Of the 1002 included 15 were excluded from analysis due to unsuccessful phlebotomy. Of the 992 included participants at the first time point, 68 had positive SARS-CoV-2 antibody tests, giving a seroprevalence of 6.9% (95% CI 5.4% to 8.6% n=992). Belfast had a significantly lower seroprevalence than all other sites at 0.9% (95% CI 0.2% to 3.3%, n=215, p<0.0001), and London had a seroprevalence significantly higher.849 of the 992 participants in the first round returned (86%). The median time between initial and follow up collections was 62 days. Of the 849 participants, 65 had positive SARS-CoV-2 antibody tests (7.66% CI 6.05–9.64). Of the 45 participants with positive antibody tests in the first round who attended the follow-up visit mean antibody titres increased. With Roche’s Elecsys assay, mean antibody titres increased from 84.7 cutoff index (COI) to 115.8 COI (difference 31.08, 95% CI 13.82–48.34, p=0.0007) and with DiaSorin’s LIAISON assay. mean antibody titres increased from 67.5 AU/ml to 81.4 AU/ml (13.89, 0.31–27.46;p=0.0452).Table summarising seroprevalence by site.Site Round 1(Number Reactive) Round 2(Number Reactive) First round Percentage Reactive (95% CI) Second Round Percentage Reactive (95%CI) All 992(77) 849(65) 7.76(6.26–9.59) 7.66(6.05,9.64) London 199(26) 135(20) 13.07(9.07,18.46) 14.81(9.8,21.78) Belfast 215(6) 200(4) 2.79(1.29,5.95) 2(0.78,5.03) Cardiff 178(10) 134(7) 5.613(3.08,10.03) 5.22(2.55, 10.39) Glasgow 224(20) 210(19) 8.93(5.85,13.39) 9.05(5.87, 13.7) Manchester 176(15) 170(15) 8.52(5.23,13.58) 9.82(5.42,14.05) The samples collected from the six month time point are still being processed, and results of antibody seroprevalence and antibody titre levels from this timepoint will be available before June.ConclusionsThe seroprevalence of SARS-CoV-2 antibodies amongst children of healthcare workers following the first wave in the UK was 6.9%, which was similar to the seroprevalence reported for adults in the UK at that time, and to international reports.The results from the second time point indicate that antibody titres in children infected with SARS-CoV-2 remain detectable for at least 62 days and indeed in this cohort increased.