Immunogenicity of COVID-19 booster vaccines in children receiving immunosuppressive medications.

Publication date: Jul 21, 2025

As many jurisdictions move towards seasonal COVID-19 vaccines, there remains insufficient data on optimal vaccination strategies for children with immune-mediated inflammatory diseases (IMID) treated with immunomodulatory therapies. A prospective observational cohort study was performed, with clinical data and biosamples longitudinally collected to determine the effect of immunomodulatory therapies on the antibody response to four COVID-19 vaccine doses. Antibodies against the SARS-CoV-2 spike, receptor-binding domain, and nucleocapsid proteins were measured. Following doses two and three, antibody responses were lowest in participants treated with biologic or targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs), of which TNF inhibitors were the most common. Rates of antibody decay were similar between treatment groups, but weaker initial responses in the b/tsDMARD group led to antibody levels dipping to low values within four months of vaccination. The fourth vaccine dose significantly boosted antibody levels in the b/tsDMARD group, resulting in a sustained response. Among additional samples collected from children with hybrid immunity (i. e., vaccinated and prior SARS-CoV-2 infection), no differences in antibody levels were found between participants who were or were not treated with b/tsDMARDs. These data support providers in counselling families regarding the importance of annual COVID-19 booster vaccines in children with IMID. There is conflicting evidence on the effect of immunosuppressive treatments on the antibody response to vaccination in paediatric populations. Long-term follow-up of children treated with various immunosuppressive therapies as they received booster COVID-19 vaccines demonstrated that antibody responses to the second and third vaccine dose were impaired in children treated with biologics (mainly TNF inhibitors). Deficits in the antibody response were largely corrected by a fourth vaccine dose or infection with SARS-CoV-2. Children treated with biologic therapies require a full suite of COVID-19 vaccines and should be strongly encouraged to receive seasonal COVID-19 vaccine boosters.

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