Pertussis: Why it's making a comeback in the U.S. and a possible solution

By Reuters Staff

NEW YORK (Reuters Health) - It's been clear for several years that immunity wanes after acellular pertussis vaccination, but a new study documents the effect of this waning immunity on a population level - and helps explain the resurgence in pertussis cases in the U.S.

Tami Skoff and Stacey Martin from the U.S. Centers for Disease Control and Prevention took a look back at reported pertussis cases over more than two decades (1990 to 2014).

They found that introduction of the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine in 2005 led to a short-term reduction in pertussis cases among adolescents. However, the benefits from Tdap vaccination mostly occurred in adolescents who received at least some doses of the whole-cell pertussis vaccine as infants when it was still in use.

And according to Skoff and Martin, writing in JAMA Pediatrics March 28, trends in adolescent disease were abruptly reversed in 2010, "the very year that children aged 11 years would have been the first cohort born after the 1997 transition from whole-cell pertussis to acellular vaccines to have received acellular vaccines for all doses of the childhood series."

"It turns out we did not know enough about the differences in immune responses between whole-cell and the new acellular vaccines," Dr. Mark Sawyer from University of California, San Diego and Rady Children's Hospital-San Diego, writes in an editorial. "Several studies have now shown us that the immune responses to the two types of vaccine are quite different and unfortunately the response to acellular vaccines is inferior. We are going to continue to see a lot of pertussis until new vaccines are developed."

In the meantime, the authors of a companion paper in JAMA Pediatrics suggest one possible interim solution to protecting older children and adults from pertussis: bring back the whole-cell pertussis vaccine.

Based on a mathematical model they created, Haedi DeAngelis of New Mexico State University in Las Cruces and colleagues say priming with one dose of whole-cell pertussis vaccine in infancy, followed by the remainder of the vaccine series with acellular vaccine, could lead to a sharp reduction in pertussis cases.

But whether parents will accept whole-cell vaccine is a major question. "The reason acellular pertussis vaccines were developed in the first place was because whole-cell vaccine was felt by many to have an unacceptably high rate of adverse effects," Dr. Sawyer notes in his editorial.

DeAngelis and colleagues modeled the effect of the anticipated increase in adverse effects that would accompany the reintroduction of whole-cell pertussis vaccine. They found that despite increased medical costs for vaccine-related adverse events, the net benefit in terms of pertussis prevention by using a priming dose of whole-cell vaccine remains.

"The problem is that you cannot model public perception," Dr. Sawyer notes. "Many in the vaccine policy world cringe at the idea of reintroducing whole-cell pertussis vaccine. The public reaction to rare but serious adverse effects related to whole-cell pertussis vaccine played a big role in fueling the anti-vaccine movement in the United States and many other countries."

"The current generation of parents in the United States is intolerant of any adverse events related to vaccines given to healthy children," he points out. "So, although bringing back whole-cell pertussis vaccine for a priming dose as suggested by DeAngelis and colleagues makes sense from an immunologic perspective, other considerations will make this challenging."

Dr. Sawyer concludes, "Pertussis is back. While we consider alternative pertussis vaccination strategies and develop new vaccines, we can at least do a better job of preventing pertussis-related deaths in infants by immunizing pregnant women during each pregnancy. We know that is safe and effective and is being increasingly accepted by pregnant women. As for other strategies that might include reintroduction of whole-cell vaccines, we need to be sure parents are going to go along."

This research had no commercial funding and the authors have no disclosures. They did not respond to a request for comment by press time. SOURCES: http://bit.ly/1PBkJA5, http://bit.ly/22I8sa0 and http://bit.ly/25sPS4E JAMA Pediatr 2016.

(c) Copyright Thomson Reuters 2016. Click For Restrictions - http://about.reuters.com/fulllegal.asp