The human immune response to inactivated influenza vaccination is dynamic, and it is influenced by age and prior immunity. The goal was to look for post vaccination transcriptome changes in children’s peripheral blood mononuclear cells. Blood samples were collected before and after immunisation with the quadrivalent inactivated influenza vaccine and RNA sequencing was done. There were 1,466 DEGs found in the Day 0–Day 3 group and 513 DEGs found in the Day 0–Day 7 group. Thirty-three genes were shared by both groups. On Day 3, the majority of transcriptome changes represented innate inflammation and apoptotic pathways. Day 7 DEGs were distinguished by the activation of cellular processes such as the regulation of the cytoskeleton, junctions, and metabolism, as well as the enhanced expression of immunoglobulin genes. On Day 3, DEGs were compared between older and younger youngsters, demonstrating that the older group had higher inflammatory gene expression.

Vaccine history in the previous year was characterised by robust DEGs at Day 3 with lower phagosome and dendritic cell maturation in individuals who had been vaccinated the previous year. The date of sampling, patient age, and vaccine history all had a substantial impact on PBMC responses to inactivated influenza vaccination in children. These findings shed light on the molecular pathways that are likely to be affected in time by influenza vaccination in youngsters.