To the best of our knowledge, no longitudinal study has reported the kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses in children. Here we report the results of the second round of antibody testing in children from a prospective multicentre cohort study in the UK. The protocol and initial results are available elsewhere.1, 2 Recruitment took place between April 16, and July 3, 2020, at five UK sites (Belfast, Cardiff, Glasgow, London, and Manchester) and included healthy children aged 2–15 years. Follow-up visits at all five UK sites took place between June 26, and Aug 15, 2020.
Of the 992 participants in the first round, 849 (86%) returned. Seroprevalence was measured with the Elecsys Anti-SARS-CoV-2 Total Antibody assay (Roche, Basel, Switzerland) and the LIAISON SARS-CoV-2 S1/S2 IgG assay (DiaSorin, Saluggia, Italy). The median time between initial and follow-up visits was 62 days (IQR 52–70; range 43–81). 65 (7·66%, 95% CI 6·05–9·64) of 849 tests were reactive based on the manufacturers' suggested cutoffs. This proportion was not substantially different to the seroprevalence (6·9% 95% CI 5·4 to 8·6; 68 of 992) reported during recruitment. The median age of participants with reactive antibody tests during the second round was 10 years (IQR 7–14; range 3–16). As with the baseline results, there was variation in seroprevalence between sites (appendix p 3).
45 participants with reactive antibody tests in the first round who attended the follow-up visit had reactive antibody tests in the second round. In these individuals, we observed increases in antibody titres from the first round to the second round with both assays: 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).
These results indicate that antibody titres in children exposed to SARS-CoV-2 remain at a detectable level for at least 62 days, and that in this cohort mean antibody titres increased over time. This finding is consistent with available data on antibody titres in adults.3, 4
Acknowledgments
TW reports grants from Public Health Agency during the conduct of the study. All other authors declare no competing interests.
Contributor Information
Covid Warriors research team:
Elizabeth Waxman, Derek Fairley, Gala Roew-Setz, James McKenna, Peter Mallet, Ryan Christy, Katherine Christie, Emma McManus, Christian Bennison, Kate Mullan, Aleksandra Metryka, Rebecca Moore, Kathryn Ferris, Alison Watt, Claire McGinn, Steven Foster, Jennifer Evans, Mark D Lyttle, Shazad Ahmad, Shamez Ladhani, Michael Corr, Julie-Ann Maney, and Sharon Christie
Supplementary Material
References
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