Danes Find Bundled Vaccines Don’t Weaken Immunity
Contrary to the fears of some parents, a 10-year study by Danish researchers found no evidence that combination vaccines, such as the measles, mumps and rubella shot, weakened children’s immune systems.
The study, published today in the Journal of the American Medical Assn., tracked 805,206 children born in Denmark.
Many parents have felt uneasy about vaccine safety since 2002, when the federal Institute of Medicine concluded that “multiple antigen” vaccines could theoretically over-stimulate the body’s immune system, leaving it more -- not less -- vulnerable to disease.
The new study found no increased rate of pneumonia, diarrhea, blood infections, or viral or bacterial infections of the nervous system.
The study “should be reassuring to parents,” said Dr. Margaret B. Rennels, a pediatrics professor at the University of Maryland who was not involved in the study.
The researchers, led by Anders Hviid, an epidemiologist at Statens Serum Institut in Denmark, followed all Danish children born from 1990 to 2001 who received a number of common vaccines against infectious diseases, including measles-mumps-rubella, or MMR, Haemophilus influenza type b, or Hib, and oral poliovirus.
Using the unique personal ID number assigned when each Danish baby is born, Hviid’s team was able to track information on all vaccinations and hospitalizations for illnesses related to infectious diseases.
The team found one potential adverse effect: Children who received the influenza vaccine were more likely to be hospitalized for upper respiratory tract infections than unvaccinated children.
But Hviid said the increased rate fell within the realm of chance.
The controversy over vaccines first emerged in 1998, when Andrew Wakefield, a researcher at Royal Free Hospital in London, published a study that linked the MMR vaccine with autism and bowel disease in children.
Although several studies have since discounted his association, it prompted many parents in Britain to shun the vaccine, causing a fivefold increase in mumps and a doubling of measles cases between 2002 and 2003.
Paul A. Offit, an infectious disease specialist at Philadelphia’s Children’s Hospital, said the results of the new study made sense because combination vaccines exposed children to a relatively small number of immunological agents.
He said there were about 135 antigens used in standard childhood vaccines -- a number dwarfed by antigens that naturally occur in the body.
“When you compare that to the 10 trillion cells that are part of our body, or the 100 trillion bacteria that live on the surface of those cells, you see just how small a threat the antigens in today’s vaccines pose,” Offit said.
