Children infected with pre-Omicron variants mount a sustainable and more effective antibody response against Omicron compared to adults

SEERY, VANESA; RAIDEN, SILVINA; RUSSO, CONSTANZA; BORDA, MAURICIO; HERRERA, LARGIÓN; URANGA, MACARENA; VARESE, AUGUSTO; CHIRINO, CARINA; SANANEZ, INÉS; GEFFNER, JORGE; ARRUVITO, LOURDES

Córdoba

Workshop; IUIS-ALACI-ASCAI2-IMMUNO-ARGENTINA 2022; 2022

Background: Despite that the clinical course of pediatric COVID-19 is usually asymptomatic or mild, SARS-CoV-2 infection results in the development of an antibody response and the generation of memory B and T cells. However, contradictory observations have been published when the antibody responses of children and adults were compared in terms of strength, specificity and perdurability.Methods: We studied the antibody response within 7-17 months after SARS-CoV-2 infection in three cohorts: unvaccinated children (n=115), unvaccinated adults (n=62), and vaccinated children (n=59). Plasma levels of anti-spike IgG antibodies and neutralizing activity against the ancestral variant (Wuhan) and the variants of concern Delta and Omicron were analyzed. Findings: More than 95% of infected children and adults remained seropositive. Titers of anti-spike IgG antibodies and plasma neutralizing activity against Wuhan, Delta and Omicron variants were significantly higher in children compared to adults. Among children, no differences were found when they were stratified by age, sex or presence/absence of symptoms at admission, but a slight decrease in the antibody response was observed in children with comorbidities. Vaccination of previously infected children with two-doses of the inactivated BBIBP-CorV or the mRNA vaccines, BNT162b2 and/or mRNA-1273 further increased anti-spike IgG titers and plasma neutralizing activity against Wuhan variant, but only mRNA vaccines significantly enhanced neutralizing titers against Delta and Omicron variants. Interpretation: Children mount a more potent and sustained antibody response compared with adults. Vaccination further increases the antibody response in previously infected children but important differences were observed according to the type of vaccine used.