Backgrounds:

Data are scarce on the nature of breakthrough infections in children following vaccination with mRNA SARS-COV-2 vaccines , especially those with rheumatic diseases (RD).

Methods

This is a prospective, observational study conducted in the second largest pediatric hospital of the country and a reference centre for children with COVID-19 from the age-appropriate release of the (BNT 162b2) mRNA COVID-19 vaccine (May 2021/16-21 years and September 2021/11-15 years of age) until December 31st, 2021. We aimed to monitor breakthrough infections in children aged <18 years old with RD on systemic treatment after the completion of the two-dose vaccination scheme.

Results:

By November 2021, 249 patients had completed their two-dose vaccination scheme. None of the patients was infected in between the two doses. However, 29 (11.6%) patients experienced SARS-CoV-2 infection following completion of the vaccination. Diagnosis was confirmed by RT-PCR in all individuals. Mean time from last dose to disease onset was 79.4 days (SD+/- 43.2). All patients were advised to avoid immunosuppressive treatment during acute illness or for a week if asymptomatic. Five patients were asymptomatic (tested due to infection exposure) while the rest presented with common symptoms. One required hospitalization due to dehydration, none required PICU admission. No RD relapse was noted.

Mean anti-spike-SARS-COV-2-IgG concentration measured simultaneously at disease onset was 234 iU/ml (SD+/-143). There was no association noted between level of antibody protection, age, disease type or medication received and symptomatic disease.

Conclusions/Learning Points:

Although patients with RD mount a significant anti-spike-SARS-COV-2-IgG antibody response, infection is not fully avoidable. If the third dose would have rendered these patients fully shielded against SARS-COV-2 or whether previous vaccination warranted protection against a more severe COVID-19 course are questions that remain to be answered.