Study: Kids have stronger COVID-19 antibody response than adults

A new prospective study of 252 families with members diagnosed as having mild COVID-19 in Italy finds that, while all age-groups had detectable SARS-CoV-2 antibodies up to 1 year after infection, children—especially those younger than 3 years—had higher antibody levels than adults at all intervals tested.In the study, published today in JAMA Network Open, a team led by University of Padua researchers enrolled 902 unvaccinated patients at a COVID follow-up clinic from Apr 1, 2020, to Aug 31, 2021.

Families were included in the study if they had children younger than 15 years and at least one member who had tested positive for COVID-19 at least 4 weeks earlier.The families underwent serologic testing for SARS-CoV-2 spike receptor-binding domain immunoglobulin G (S-RBD IgG) antibodies one to three times at 1 to 4, 5 to 10, and/or over 10 months after infection.Detectable but declining levelsOf the 902 patients, 697 had either tested positive for COVID-19 (575; 63.7%) or had detectable SARS-CoV-2 antibodies despite no other evidence of infection (122; 17.5%), including 351 children and older siblings (average age, 8.6 years) and 346 parents (42.5 years).

Among the 697 infected patients, 674 (96.7%) were asymptomatic or had mild symptoms.At all time-points, children had significantly higher antibody concentrations than adults, with a median S-RBD IgG level fivefold higher in those younger than 3 years than in older participants.

Of the 659 participants who had their antibody levels checked at least once, 657 (99.7%) still had detectable antibodies during follow-up after 64 days, while 2 of 659 (0.3%) of infected participants had negative antibody results after 556 days.No patients reported a subsequent infection or exposure