Comparison of antibody responses to SARS-CoV-2 variants in Australian children

Abstract

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 neutralization test (% inhibition). 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 (geometric mean concentration 46.4 binding antibody units/ml; % inhibition = 16.3%) mounted a significantly lower antibody response than Delta (435.5 binding antibody untis/mL, % inhibition = 76.9%) or Wuhan (359.0 binding antibody units/mL, % inhibition = 74.0%). Vaccinated children with breakthrough Omicron infection mounted the highest antibody response (2856 binding antibody units/mL, % inhibition = 96.5%). Our findings suggest that despite a high seropositivity 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.

Immunological imprinting of humoral immunity to SARS-CoV-2 in children

“…Serological samples prior to the Omicron infection were available from 15 children of whom 4 were SARS-CoV-2 seronegative (primary infection) and 11 seropositive (secondary infection). Primary Omicron infection elicited low antibody titres against both the ancestral spike and RBD domains ( Figure 1A, Extended Data Figure 2A ), consistent with previous reports ( 18 ). Titres against Delta variant were high in one child, likely due to subclinical Delta infection between blood sampling, and as such this was regarded as a secondary infection ( Extended Data Figure 2A ).…”

Immunogenicity of coronavirus disease 2019 vaccines in children: A review with ChatGPT

“…In unvaccinated children, infected with the ancestral, Delta or Omicron variants and children with at least one dose of vaccine and a breakthrough Omicron infection, children who were both vaccinated and infected had higher neutralizing capacity against the ancestral variant than children who were unvaccinated but infected with the ancestral, Delta, or Omicron variants. 69 This confirms the concept that hybrid immunity generates more potent antibody responses than infection alone. Amongst children who were infected with the Omicron variant, vaccinated children also had a significantly higher neutralization response against Omicron than unvaccinated children.…”

T cell hybrid immunity against SARS-CoV-2 in children: a longitudinal study

“…This has been well documented in adults 47 , 48 , 49 , 50 and recently explored in children with hybrid immunity. 51 , 52 We tested the sera of children with breakthrough infection (visit 5, n = 25) and vaccinated-only children (visit 3, n = 134, including data from an extended cohort; Table 2 ) with a surrogate virus neutralisation test (sVNT) 53 to assess their ability to inhibit the binding of hACE2 to wildtype S-RBD and variant S-RBD (Alpha/B.1.1.7, Beta/B.1.351, Gamma/P.1, Delta/B.1.617.2, Delta+/B.1.617.2.1, Lambda/C.37, Mu/B.1.621, and Omicron/B.1.1.529, Omicron sublineages BA.2/BA.5, XBB, XBB.1.5 and SARS-CoV-1). We confirmed that sera of children with hybrid immunity had a strongly improved capacity to cross-neutralise SARS-CoV-2 variants over children with non-hybrid immunity from vaccination alone ( Fig.…”