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article imageWhooping cough has evolved - vaccine has been outsmarted

By Karen Graham     Dec 29, 2014 in Health
There has been a global resurgence in the number of cases of whooping cough in the past decade. Researchers say this may be because the bacterium that causes the disease has been able to outsmart the current vaccine being used.
In 2012 in the U.K. and Wales, almost 10,000 cases of whooping cough were confirmed, leading to the death of 14 infants under three months of age. This led scientists to examine the genetic makeup of the pertussis bacterium that causes whooping cough. The results of that study found that parts of the bacteria the vaccine "primes" the immune system to recognize and fight the pertussis have changed.
“This was much greater than the previous recent "peak" year in 2008, in which 902 cases were reported despite levels of vaccine coverage and diagnostic methods not changing during this period,” said the authors of the study that was published in the Journal Of Infectious Diseases this month.
Gram stain of the bacteria Bordetella pertussis.
Gram stain of the bacteria Bordetella pertussis.
CDC
In the United States, the number of cases of whooping cough for the year 2013 was 28,639, with 12 deaths of infants aged three months or younger. The number of cases of whooping cough reported this year, 2014, are significantly higher. The California Department of Public Health reported a total of 9,935 cases of whooping cough in the state from Jan. 1 to Nov. 26, 2014. This is the highest number in 70 years. And this is not taking into account the number of cases in the other 49 states.
In studying the Bordetella pertussis genomes, the researchers found that the “acellular vaccine antigen encoding genes are evolving at higher rates than other surface protein-encoding genes,” along with some other things. But the primary finding was that switching to the use of the whole cell (WCV) to acellular (ACV) pertussis vaccines may be the reason for the rise in the number of cases.
Researchers were quick to add that the evolution taking place in the B. pertussis bacterium started before the U.K. and U.S. switched from using the whole cell (WCV) vaccine to the acellular ACV vaccine. In 2004, an acellular vaccine was introduced because of the side effects the whole cell vaccine produced. These included pain and swelling from the shot itself, along with fever.
The study also found that the whole cell vaccine gave better protection against the whooping cough, producing a longer immunity. But the most significant part of the study showed that the acellular vaccine may actually be creating a pool of carriers, especially among teens, and might be helping to spread the disease faster.
The BBC summarized the B. pertussis study quite well: “They found proteins being targeted by the vaccine were mutating at a faster rate than other surface proteins not included in the vaccine. Potentially it means the bacteria is changing quickly to get around immune system’s defenses put in place with immunization.”
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