Vaccine Refusals Tied to Pertussis Outbreak

September 30, 2013

News Review From Harvard Medical School -- Vaccine Refusals Tied to Pertussis Outbreak

Clusters of children who didn't get shots contributed to a major outbreak of pertussis in California, a study suggests. Pertussis is also called whooping cough. The 2010 outbreak was the largest in more than 60 years. More than 9,000 cases and 10 deaths occurred. All states require children to get vaccines before they enter kindergarten. One of the vaccines helps prevent whooping cough. But California allows exemptions for many non-medical reasons. Researchers looked at patterns of non-medical exemptions in the state. They focused on the years 2005 through 2010. They found 39 areas of the state with large clusters of exemptions. They also found 2 areas of the state that had high rates of whooping cough in 2010. Census districts in exemption clusters were 2.5 times as likely to have high rates of whooping cough as areas with fewer exemptions. Areas with a lot of exemptions or whooping cough cases had other things in common, too. They tended to have higher household incomes, smaller families and fewer minorities than average. The journal Pediatrics published the study online. USA Today and MedPage Today wrote about it September 30.

By Claire McCarthy, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Vaccines prevent all sorts of diseases. The more people who vaccinate, the less common the diseases become. But when people choose not to vaccinate, the diseases come back.

This is common sense, entirely unremarkable. But it's something we don’t think about enough. A study just released in the journal Pediatrics brings it home.

Researchers looked at parents who chose not to vaccinate their children. They did not include people who made this choice for a medical reason. For example, children on chemotherapy or some other medicines can't be vaccinated. Neither can those with certain medical conditions or allergies. Rather, this study focused on people who simply chose not to get shots for their children. Researchers compared vaccine refusal rates with the rate of pertussis in California.

Pertussis is also known as whooping cough. Before the vaccine was introduced in the 1940s, it was the leading cause of childhood death in the United States.  The vaccine has been remarkably effective. In 1934, there were more than 265,000 cases of pertussis. In 1976, there were only 1,010.

But in the 1990s and early 2000s, we started to see more cases. In 2004-2005, the number was up to more than 25,000. In 2010, California had 9,120 cases, one-third of all the cases in the country. There were 10 deaths in the state.

At the same time, the number of people choosing not to vaccinate was going up. Between 2000 and 2010, the rate of non-medical exemptions tripled, from 0.77% to 2.33%. This may seem low. In fact, more than 90% of incoming kindergartners have all of their shots. But it's important to realize that many of the people who chose not to immunize lived in the same areas. Researchers found that in some communities the rates of not immunizing were as high as 84%.

That’s why it's not surprising that areas with lots of people choosing not to vaccinate were 2.5 times as likely to have cases of pertussis.

What Changes Can I Make Now?

This one's simple: Get your child all the recommended vaccinations. Vaccines save lives. As this study points out, it's not just your child's life that can be saved, but also the lives of everyone around you. Because of vaccines, we have wiped out polio in the United States. We hardly ever see epiglottitis caused by the bacteria hemophilus influenzae. Chickenpox has dropped dramatically.

And that's what's really important. All medical treatments have risks, and vaccines are no exception. But in every case, the risk of complications from the vaccine is lower than the risk of complications from the diseases they prevent.

Read about vaccines and vaccine-preventable diseases. The Centers for Disease Control and Prevention has a great website with everything you might want to know.  Talk to your doctor if you have any questions.

If you do vaccinate your children, talk to your friends, family and neighbors about your choice. Be a voice of reason and encouragement.  We need those voices.

What Can I Expect Looking to the Future?

If more parents choose not to vaccinate their children, we will see the resurgence of diseases that vaccines prevent. As this study shows, we are seeing more pertussis. We've also been seeing more cases of measles. If we don't turn this around and get more children immunized, we will see even more of these diseases.

I hope that won't happen. I hope that studies like this one will be a wake-up call, and help us change direction.