One of the most hotly debated topics among parents is vaccination: if it saves lives, if it harms lives, when to do it, how often to do it, et cetera.  A study published recently in Environmental Health Perspectives may just add another cog to the debate: whether or not vaccines are effective at all, particularly for children who have been exposed to environmental toxins.

For the study, researchers measured PCB concentrations and antibody levels in the blood of pregnant women and their children from the Faroe Islands, a Nordic fishing community in the North Atlantic Ocean.  PCBs, or polychlorinated biphenyls, are environmental contaminants that were commercially produced for a range of applications since the 1920s. They have since been banned around the world, but they are still commonly found in the environment and in our food.  According to their report, PCB exposure among the Faroese is notoriously high because this community rely heavily on pilot whale blubber, which is loaded with PCBs, for food.

So researchers collected blood samples from pregnant mothers in their 32nd week of pregnancy and from their children at 3, 5, 12 and 18 months and at 5 and 7 years of age. Breastmilk was also collected and the blood and milk were analyzed for total PCB contamination.

Children in the study received vaccinations against tetanus and diphtheria, following a standard vaccination schedule, at 3, 5, and 12 months, and then again at 5 years.  Antibody concentrations against tetanus and diphtheria were measured in all blood samples.

What did they find after analyzing all of this data?  The researchers found that increased levels of PCBs in a child's blood were strongly associated with decreased antibody concentrations as the children got older.  In fact, before receiving the booster vaccine, 37 percent of the 5-year-olds had antibody concentrations that were insufficient for protection. And at age 7, children with high PCBs at 18 months had reduced concentrations of antibodies against both tetanus and diphtheria.

In other words, cumulative PCB exposure early on in a child's life - particularly levels measured around 18 months – can reduce the development of antibodies in response to diphtheria and tetanus vaccines.  And this reduction in antibodies can potentially make children vulnerable to diseases, even if they have been vaccinated for them.  

Does this mean that we should all just skip the vaccines.  Not at all.  It's unlikely that any of us see the kind of PCB exposure that they do in a whale blubber eating community.  But it does explain why some children may still be susceptible to disease even after vaccination.  And why we need to test chemicals for safety before introducing them to our environment in the first place.