Tags: whooping | cough | outbreaks | vaccine | pertussis

Whooping Cough Outbreaks Traced to Vaccine Changes

By    |   Friday, 24 April 2015 03:44 PM

Many health experts have blamed recent outbreaks of whooping cough in the United States on the growing number of parents who are opting not to vaccinate their children. But new research suggests another fact is also at work: A change made two decades ago to vaccine ingredients.

In 2012, the United States had about 48,000 cases of whooping cough (also called pertussis) — the most cases since 1955 and nearly five times as many cases as there were between 1965 and 2002, according to the Centers for Disease Control and Prevention.

While some public health officials have suggested tied the increase to fewer children were getting the vaccine, the new study indicates a change in vaccine ingredients may be a key factor, Fox News reports.

The study, published in Public Library of Science journal PLOS ONE Computational Biology, tracked whooping cough cases in the U.S. from 1950 to 2009 caused by the bacterium Bordetella pertussis, which infects the respiratory system.

Lead researcher Manoj Gambhir, an associate professor of epidemiology at Monash University in Melbourne, Australia, noted doctors began vaccinating against pertussis in the 1940s with a so-called “whole-cell vaccine,” comprised of dead bacteria.

This type of vaccine "can raise an immune response, but cannot cause the disease," said Gambhir, noting the vaccine reduced whooping cough rates dramatically between the 1950s to the 1980s.

But the whole-cell vaccine caused rare side effects, such as fevers and convulsions. So, in 1991, a new, "acellular" vaccine that does not contain dead bacterial cells was developed that "contains far fewer components of the bacteria and, therefore, far fewer possible biochemical triggers for the adverse events," Gambhir told Live Science.

Doctors began using the acellular vaccine in the U.S. during the 1990s, but it turned out to be less effective than the original vaccine — preventing 80 percent of cases, compared with the 90 percent the whole-cell vaccine prevented, Gambhir said.

Two whooping cough outbreaks — in 2010 and 2012 — were mainly in 7- to 13-year-olds, suggesting the vaccine was a factor.

"The lower level of protection of this group of kids is well explained by the fact that they were among the first group to be entirely vaccinated by the acellular vaccine," Gambhir said.

Pritish Tosh, M.D., an infectious-diseases physician at the Mayo Clinic, said the findings underscore the need to develop a pertussis vaccine that is both safe and effective, but stressed that parent should continue to vaccinate their children with the existing shot.

"In the long run, we may need to have newly designed pertussis vaccines that give a broader and longer-lasting protection," he said.

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A change made two decades ago to the whooping cough vaccine may be partly to blame for a resurgence in cases in recent years.
whooping, cough, outbreaks, vaccine, pertussis
Friday, 24 April 2015 03:44 PM
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