Whooping Cough Study May Offer Clue on Surge
Baboons vaccinated against whooping cough could still carry the illness in their throats and spread it, research published in a science journal on Monday has found. The surprising new finding has not been replicated in people, but scientists say it may provide an important clue to a puzzling spike in the incidence of whooping cough across the country, which reached a 50-year high last year.
The whooping cough vaccines now in use were introduced in the 1990s after an older version, which offered longer-lasting protection, was found to have side effects. But over the years, scientists have determined that the new vaccines began to lose effectiveness after about five years, a significant problem that many researchers believe has contributed to the significant rise in whooping cough cases.
The new study, published on Monday in Proceedings of the National Academy of Sciences, offers another explanation. Using baboons, the researchers found that recently vaccinated animals continued to carry the infection in their throats. Even though those baboons did not get sick from it, they spread the infection to others that were not vaccinated.
“When you’re newly vaccinated you are an asymptomatic carrier, which is good for you, but not for the population,” said Tod J. Merkel, the lead author of the study, who is a researcher in the Office of Vaccines Research and Review in the Food and Drug Administration.
Scientists said the finding was surprising, and could be a signpost for investigators as they try to improve the vaccines for people.
“If Dr. Merkel is correct, then we need to develop better acellular vaccines,” said Dr. Stanley Plotkin, an emeritus professor of pediatrics at the University of Pennsylvania. The new vaccines are known as acellular, as they contain purified proteins, instead of complete bacteria that have been killed. “A great deal of thought and discussion is being devoted to that at the moment,” he said.
The current vaccines, usually administered in infancy, preschool and adolescence, protect well in early childhood. But by adolescence, the protective effects wane quickly. Doctors often recommend boosters. Death from whooping cough can occur in infants, but is unusual in adults.
The current whooping cough vaccines were developed after a surge in concerns from parents that their children were getting fevers and having seizures after receiving the old vaccine. Those worries added fuel to general skepticism about vaccines that had led some parents to choose not to have their children vaccinated.
But scientists say the problem of surging whooping cough cases has more to do with flaws in the current vaccines than with parents’ resistance. The new finding suggests yet another weakness of the vaccine — that even people recently vaccinated may be continuing to spread the infection without getting sick.
“The baboon model has provided an illuminating insight into the epidemic as we are coping with it today,” said Dr. William Schaffner, a professor of preventive medicine at Vanderbilt University, who was not involved in the study.