Can Common Childhood Vaccine Protect Against Leukemia?

Acute lymphoblastic leukemia accounts for nearly 25% of cancer diagnoses in children under 15 years of age.

A common vaccine administered in childhood may protect against acute lymphoblastic leukemia (ALL), which is the most common type of cancer in children.

A study published recently in Nature Immunology found that Haemophilus influenzae Type b (Hib) vaccine can not only stop ear infections and meningitis caused by Hib bacterium, but also can protect against ALL. The Hib vaccine is routinely administered to children prior to 15 months of age in 4 doses as part of the standard vaccination regimen recommended by the US Centers for Disease Control and Prevention.

The researchers found that recurrent Hib infections can activate certain immune-system genes that convert blood cells into cancer.

"These experiments help explain why the incidence of leukemia has been dramatically reduced since the advent of regular vaccinations during infancy," senior author Markus Müschen, MD, PhD, said in a press release. "Hib and other childhood infections can cause recurrent and vehement immune responses, which we have found could lead to leukemia, but infants that have received vaccines are largely protected and acquire long-term immunity through very mild immune reactions."

The study evaluated the notion that chronic inflammation from recurrent infections may cause additional genetic lesions in blood cells that already carry an oncogene, which promotes the transformation to overt disease.

The researchers conducted experiments with mice that targeted the AID and RAG enzymes as drivers of the process. These enzymes introduce DNA mutations that allow immune cells to adapt to infectious challenges.

In cases of chronic infection, however, the researchers found AID and RAG are put into overdrive to randomly cut and mutate genes, including those that protect against cancer.

The researchers will next conduct experiments to evaluate if leukemia protection is also offered by vaccines against viral infections, including the MMR vaccine.

"The study provides mechanistic support for the hypothesis that infection or inflammation promotes the evolution of childhood leukemia and that the timing of common infections in early life is critical," said co-author Mel F. Greaves, MD, PhD, in a press release.