What do Vaccine Fears Cost?

MMR vaccine controversy causes childhood vaccination rates to decline

(RxWiki News) What can happen when bad research impacts your kids? In the case of vaccines, parents start to distrust all childhood vaccinations.

A recent study has confirmed what several doctors and public health officials have feared: childhood vaccination rates declined after the study that (falsely) linked autism to the measles-mumps-rubella (MMR) vaccine was debunked.

The problem is that parents who believe they may be "playing it safe" by skipping the vaccination put their children and others in the community at risk.

"Are you keeping your children up-to-date on vaccinations?"

Lenisa Chang, an economics professor at the University of Cincinnati's Carl H. Lindner College of Business, will be presenting her study on the MMR-autism controversy at a conference this June.

In 1998, Andrew Wakefield, who has since lost his medical license in England, published a small, flawed case study in The Lancet that attempted to link the MMR vaccine to autism.

British investigative journalist Brian Deer uncovered a range of scientific flaws in the study, which was retracted from The Lancet two years ago, and several dozen studies since then have thoroughly debunked any connection between any vaccines and autism.

Yet the public fear stirred up by the initial publicity of the paper has had a lasting impact on vaccination rates.

Chang analyzed the data from the National Immunization Survey from 1995 through 2006 and found that about two percent fewer US parents gave their children the MMR vaccine in 1999 and 2000.

Though two percent sounds small, it translates into many thousands of children not receiving the vaccine, which can erode the immunity of communities against mumps, rubella, and especially measles.

"The Wakefield report in The Lancet is proof that an extraordinary claim made without evidence can do a lot of harm," said Dr. Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia and the inventor of the RotaTeq vaccine. "Peer reviewers and editors of major medical journals should use this as a cautionary tale of just how powerful bad studies can be."

The MMR vaccination rates did begin to rebound somewhat each year thereafter, with only 1.5 percent fewer vaccinations in 2001, 1.3 percent in 2002 and 1 percent in 2003. Yet the rate did not completely return to its pre-1998 levels for the study period included, Chang told dailyRx.

"By 2004 and 2005, it seemed the medical community had reached a consensus that the vaccine was okay, but the gap didn't close," Chang said.

Among Chang's findings was a relationship between the education of the parents and the likelihood that they would not get the MMR vaccine for their children.

The children of college-educated mothers had lower vaccination rates than children of mothers who had not completed a college education - and this trend continued long after the later studies debunking the link between the MMR vaccine and autism.

"I expected that you would have seen college-educated mothers start vaccinating their children at the same rate as other mothers," Chang said. "More educated people tend to have better access to health information, and they're more likely to change their behaviors based on that."

Though her study did not delve into the reasons these parents elected to continue not vaccinating, Chang mentioned past research that may provide some clues to the reasons.

"We know that more college-educated people tend to be more risk-averse," Chang said. "Until they believe more of the conclusions, they may not vaccinate their children, and people are also getting their information from other sources, like the Internet."

Plus, a bit of psychology may have been at play, Chang hypothesized.

"People tend to put more weight in their decisions based on negative information. It's much harder to undo the effect of that information when you get positive information later," she said. "It's much harder than the other way around, where you get positive information first and then the negative information."

In other words, even the many studies showing that the MMR vaccine was safe and had no link to autism, the power of the fear implanted by the initial study remained for many parents. 

"We know that all vaccines have a small risk, but if some people think the risk is higher and think they're choosing to take the safe approach, then the protection you get through herd immunity is no longer there," Chang said. "Then a lot of people will suffer because someone tried to play it really, really, really safe at one point."

In fact, a number of public health officials have said that the exceptionally high number of measles cases announced by the Centers for Disease Control and Prevention last month may be related to lower rates of measles vaccination.

Chang also looked at the rates of the DTaP (diphtheria-tetanus-pertussis) vaccine and the polio vaccine and was initially surprised by what she found. Until Wakefield's study, most children had completed their round of polio vaccinations, which involves three shots.

The third shot, however, according to the CDC schedule, is given at the same well child visit as the MMR shot. Chang found that the rates of children receiving the third shot of polio also declined after 1998.

"It did not decrease as much as the MMR, but it definitely decreased from 2000 to 2003, then it went back up to the level it had been before," Chang said. She suspects that parents may have been concerned about other vaccines now that one vaccine was being linked to autism, creating a "spillover effect" of sorts.

“The spillover effect I find on other vaccines such as polio and, to a lesser degree DTaP (diphtheria, tetanus and pertussis), could be partially ascribed to general safety concerns toward all vaccines that stemmed from the MMR controversy, but other factors might be at play as well,” Chang said.

Vaccines have been the subject of controversy since their inception, but Dr. Offit points out that the skeptics of vaccines do others a disservice when they promote misinformation that is contradicted by the medical evidence.

"Those who warn against using vaccines are no different than those who shout fire in a crowded movie theater. It's advice that puts everyone at risk," Dr. Offit said. "Anyone who reads carefully through studies that evaluate the safety and efficacy of vaccines will be reassured that vaccines are exactly what they're claimed to be. It's an evidence-based system. Read the evidence."

Chang's study will be presented during the 4th Biennial Conference of the American Society of Health Economics June 10-13 in Minnesota. Information regarding funding was unavailable.

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Review Date: 
June 6, 2012