# Humoral and Innate Immunological Profile of Paediatric Recipients of Pfizer-BioNTech BNT162b2 mRNA Vaccine

## TL;DR

This study examines how children's immune systems respond to the Pfizer-BioNTech mRNA vaccine, finding strong antibody responses and changes in immune cell counts.

## Contribution

The study provides new insights into the immune response of children to the Pfizer-BioNTech vaccine, including sustained humoral immunity and interferon pathway sensitization.

## Key findings

- Paediatric recipients show a robust and sustained humoral response for at least three months.
- The vaccine causes transient lymphocytopenia similar to viral infections.
- The vaccine may sensitize the interferon signaling pathway for stronger future responses.

## Abstract

The Pfizer-BioNTech vaccine was one of the essential tools in curtailing the COVID-19 pandemic. Unlike conventional vaccines, this newly approved mRNA vaccine is taken up by cells, which leads to the synthesis of the specific viral Spike antigen. The vaccine was initially introduced for adults, and the immunological profile of adult recipients is well-characterized. The vaccine was approved for paediatric use much later after its efficacy and safety had been confirmed in children. However, the complete picture of how the paediatric immune system in children reacts to the vaccine is not well documented. Therefore, in order to better understand the immune response in children, we analysed the humoral response, immune cell count, and interferon signalling in paediatric vaccine recipients ranging between 5 and 17 years of age. Our findings suggest that the paediatric recipients elicit a robust humoral response that is sustained for at least three months. We also found that the vaccine triggered a transient lymphocytopenia similar to that observed during viral infection. Interestingly, we also found that the vaccine may sensitise the interferon signalling pathway, priming the cells to mount a potent response when exposed to interferons during a subsequent infection. The study offers new insights into the workings of the paediatric immune system and innate immunity, thereby opening the doors for further research in this field.