Does Vaccination Prevent Cancer?

7 03 2011

The history of anxiety about possible negative effects of vaccines is long, tracing back at least as far as Benjamin Franklin. Countering these worries is the fact that vaccines are one of the greatest public health successes of our time, saving millions of lives worldwide.

Now we know that vaccine benefits may extend beyond prevention of the target childhood disease.

An already recognized extra benefit comes with the vaccines for varicella. A varicella vaccine not only can prevent chickenpox in young people, but may also stop the occurrence of shingles in older folks.

Shingles, a neurological attack by the chickenpox virus decades after an infection, can cause a rash that leaves behind chronic, unbearable pain. Vaccination in childhood may protect against shingles, and according to a new study from a Texas group, published in The Journal of Pediatrics, childhood vaccines may offer reduced odds of childhood cancer.

The researchers, going on hints from earlier studies, looked at vaccine rates in specific areas and compared those numbers to childhood cancer rates in the same region. While childhood cancers are rare, they are, of course, devastating. The most common cancers in children are leukemia and brain and spinal cord cancers. According to previous studies, some common childhood infections might increase a child’s risk of leukemia, while vaccinations might reduce that risk. It’s not a nutty idea that some infections—especially viral infections—might be associated with cancer. Indeed, a few viral infections have an established association, including human papillomavirus (HPV, associated with cervical and anal cancers), hepatitis B (associated with liver cancer), and Epstein-Barr (the “mono” virus, linked to a type of lymphoma).

The researchers looked at the 2800 cases of childhood cancer diagnosed in Texas from 1995 to 2006, focusing only on cases diagnosed in children two years or older. For every child diagnosed with cancer, the team identified four more children who had not had cancer, matched for age and sex. As a final step, they then mapped how many children from each group had been born in Texas counties with high vaccination rates.

Their results showed that where hepatitis B vaccination rates were high, odds of all childhood cancers fell by almost 20%. Where rates of inactivated polio virus, hepatitis B, or a specific mix of childhood vaccinations were high, odds of finding cases of a common childhood leukemia, acute lymphoblastic leukemia (ALL), dropped by as much as 38%. The biggest dip in odds came with higher rates of Hib (Haemophilus influenzae type b) vaccine and ALL, with a 42% decrease in ALL odds where Hib vaccination rates were high.

It’s important to remember that the authors didn’t establish a cause–effect link here. This study is based on the numbers, and the take-home message here is a simple one. The authors put it best in their abstract: “Some common childhood vaccines appear to be protective against ALL at the population level.”


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