Several epidemiological studies investigated potential associations between vaccination
in childhood and childhood cancer. However, results were inconsistent and a meta-analysis
on this topic is lacking.
Systematic searches of the PubMed and Web of Science databases on childhood cancer
and vaccination were conducted. We identified 4,163 studies, of which 52 studies fulfilled
the inclusion criteria for this review. Pooled odds ratios (OR) were calculated using
random effects models if three or more studies for a specific research question in
this field were available.
Overall, we observed 75 effect estimates for decreased risks of different childhood
cancer types after specific vaccinations, 16 for increased risks, and 351 for non-significant
associations within the included studies. Ten studies presented data on associations
between specific vaccines and childhood leukemia allowing meta-analyses of four associations.
Compared to children without the specific vaccination, the pooled OR of leukemia risk
was 1.05 [(95% CI: 0.74, 1.49), number of studies N = 5] for Bacille Calmette-Guérin
vaccination, 0.92 [(0.75, 1.14), N = 3] for Hepatitis B vaccination and 1.04 [(0.84,
1.30), N = 4] for Poliomyelitis vaccination. Using the total number of vaccine injections
as exposure variable, we observed an OR of 0.63 (0.26, 1.51) for childhood leukemia
in children with a high number of injections (> 4 injections) compared to children
without injections based on 3 studies.
The pooled analysis of previous studies does not support the hypothesis regarding
an association between vaccination and the risk of childhood leukemia. However, all
52 studies had at least one of the following limitations: small sample size, invalid
exposure assessment or lack of adjustment. Large studies with valid exposure assessment
on immunization and detailed information on possible confounders (e.g. other vaccines,
infections) are needed.
