Old vaccine, new tricks: Revive early pertussis shot, study says

Six year old girl coughs diseased lying in bed with a thermometer on the mouse (iStock)

Newer isn't always better — some researchers are proposing to bring back an older version of the whooping cough vaccine, because multiple studies show that today's version doesn't protect as well as the earlier kind.

In a new study, researchers suggest vaccinating children with one dose of the older whooping cough vaccine — called the whole-cell pertussis vaccine — and then giving them four doses of the current whooping cough vaccine in early childhood. (Whooping cough is also known as pertussis.) Currently, children are given five doses of the new vaccine.

Using a mathematical model, the researchers found that this "combined" vaccination strategy could reduce the rate of whooping cough infections by up to 95 percent, and save millions of dollars in health care costs. Researchers from The Santa Fe Institute, a nonprofit research center in New Mexico, conducted the study.

The older, whole-cell pertussis vaccine is linked with a higher rate of side effects, such as fever, than is the newer version. But because improved vaccines against whooping cough are likely years away, "in the interim, switching to the combined strategy is an effective option for reducing the disease and mortality" from whooping cough the researchers wrote in their findings, published today (March 28) in the journal JAMA Pediatrics. [5 Dangerous Vaccine Myths]

But even though the new study found that the benefits the combined strategy would outweigh the risks, questions remain about whether parents would accept a higher rate of side effects, especially among those parents who are already hesitant to vaccinate their children, experts said.

Older is better?

The whole-cell pertussis vaccine was used in the United States from the 1940s until the 1990s, when doctors switched to a new version called the acellular pertussis vaccine, which was linked to fewer side effects. But studies soon found that, unlike the older version, the acellular pertussis vaccine did not produce long-lasting immunity against pertussis; the protection offered by the acellular vaccine wanes after a few years.

Researchers have attributed the rise in whooping cough cases in recent years in part to the inferior protection offered by the acellular vaccine. In 2012, there were more than 48,200 cases of whooping cough in the United States, the most in any year since 1955.

The current vaccine schedule calls for five doses of the acellular vaccine, with one dose occurring at each of the following times: ages 2 to 4 months, 4 to 6 months, 6 to 8 months, 18 to 24 months, and 4 to 5 years. In the new study, researchers compared using that schedule with a "combined" vaccine strategy, of giving an initial dose of the whole-cell pertussis vaccine followed by four doses of the acellular pertussis vaccine.

The combined strategy would reduce symptomatic whooping cough cases by 95 percent, and would reduce cases in infants by 96 percent, compared with the current strategy, the models predicted. With the combined strategy, there would also be a 96 percent decrease in hospitalizations from whooping cough and a 95 percent decrease in infant deaths from the disease, compared with the acellular strategy.

However, the combined strategy would have higher rates of vaccine side effects: There would be about 10 more cases of fever for every 100,000 vaccinations, and seven more cases of seizures for every 10 million vaccinations, compared with the acellular vaccine strategy.

Overall, the combined strategy would lead to a 96 percent decrease in hospitalizations due to either whooping cough or vaccine-related side effects, the study found.

Public perception

Based on the new study, it seems the combined strategy would lead to better outcomes overall, said Dr. Amesh Adalja, an infectious-disease specialist and a senior associate at the University of Pittsburgh Medical Center's Center for Health Security. "When you look at the way they've modeled this, it seems to be, on balance, a better strategy than what we're doing currently," Adalja said.

And giving just one dose of the whole-cell vaccine "maybe somewhat more palatable to people" than giving children five doses of this vaccine, Adalja said.

The findings also support the idea that "the strategy we're using currently against pertussis is not the optimal model, and children are needlessly contracting pertussis because we're using an inferior vaccination strategy," Adalja said.

Still, some experts were skeptical that parents would accept bringing back the whole-cell pertussis vaccine.

"The problem is that you cannot model public perception," Dr. Mark Sawyer, a pediatric infectious disease specialist at the University of California, San Diego School of Medicine, wrote in an editorial accompanying the study in the journal. "Many in the vaccine-policy world cringe at the idea of re-introducing whole-cell pertussis vaccine."

Sawyer noted that parents today are intolerant of any adverse side effects related to vaccines, even if such effects are rare. In the past, the public reaction to these side effects played a role in the rise of the anti-vaccine movement, Sawyer said.

"Although bringing back whole-cell pertussis vaccine for a priming dose … makes sense from an immunologic perspective, other considerations will make this challenging," Sawyer said.

Because the study used a mathematical model and was not conducted in the real world, more studies will need to validate the findings before policy would be changed, Adalja said.

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