RESUMO
There is limited understanding of antibody responses in children across different SARS-CoV-2 variants. As part of an ongoing household cohort study, we assessed the antibody response among unvaccinated children infected with Wuhan, Delta or Omicron variants, as well as vaccinated children with breakthrough Omicron infection, using a SARS-CoV-2 S1-specific IgG assay and surrogate virus neutralisation test (sVNT). Most children infected with Delta (100%, 35/35) or Omicron (81.3%, 13/16) variants seroconverted by one month following infection. In contrast, 37.5% (21/56) children infected with Wuhan seroconverted, as previously reported. However, Omicron-infected children (GMC 46.4 BAU/ml; sVNT % inhibition: 16.3%) mounted a significantly lower antibody response than Delta (435.5 BAU/mL, sVNT=76.9%) or Wuhan (359.0 BAU/mL, sVNT=74.0%). Vaccinated children with breakthrough Omicron infection mounted the highest antibody response (2856 BAU/mL, sVNT=96.5%). Our findings suggest that despite a high seroconversion rate, Omicron infection in children results in lower antibody levels and function compared with Wuhan or Delta infection or with vaccinated children with breakthrough Omicron infection. Our data have important implications for public health measures and vaccination strategies to protect children.
