Immunogenicity, Safety and Effectiveness of COVID-19 Pfizer-BioNTech (BNT162b2) mRNA Vaccination in Immunocompromised Adolescents and Young Adults: A systematic Review and Meta-Analyses

People with weak immune systems are more likely to develop severe COVID-19, less likely to be included in vaccine controlled studies but more likely to be under-vaccinated. We review post-marketing studies to examine the immunogenicity, safety and effectiveness of BNT162b2 vaccine in immunocompromised adolescents and young adults (AYA). We searched more than three international databases from 2020 to 30 May 2022 and used the ROBINS-I for bias assessment. Random effect model was used to estimate pooled proportion, log RR, and mean difference. Eggers regression and Beggs rank correlation were used to examine publication bias. 47 full texts were reviewed, and nine were included. Conditions studied were rheumatic diseases, diabetes mellitus, Down syndrome, solid tumours, neurodisability, and cystic fibrosis. Eight studies used cohort designs and one used cross-sectional designs. Europe led most of the investigations. Most studies had unclear risk of bias and none could rule out selection bias, ascertainment bias, or selective outcome reporting. The overall estimated proportion of combined local and systemic reactions after the first BNT162b2 vaccination was 30%[95% CI: 17-42%] and slightly rose to 32% [95% CI: 19-44%] after the second dose. Rheumatic illnesses had the highest rate of AEFI (40%[95% CI: 16-65%]), while cystic fibrosis had the lowest (27%[95% CI: 17%-38%]). Hospitalizations for AEFIs were rare. Healthy controls exhibited higher levels of neutralizing antibodies and measured IgG than immunocompromised AYA, although pooled estimations did not demonstrate a statistically significant difference after primary dose. BNT162b2 is safe and effective in immunocompromised AYA, with no significant difference to healthy controls. However, current evidence is low to moderate due to high RoB. Our research advocates for improving methodology in studies including specific AYA population.