TUESDAY, SEPTEMBER 27, 2016

Study demonstrates vaccine confers long-lived protection against pertussis

While many speculations have been made about the recent resurgence of pertussis in the U.S., a recent study in Thailand found that pertussis vaccines may offer lifelong protection against the disease.

A team of University of Michigan-led researchers reviewed 30 years of data in Thailand to determine if the pertussis vaccine either wears off faster than previously believed or if it fails to protect against transmission of the bacterial disease. The team found that the vaccines provided long-lived, potentially life-long, protection against the disease and that the vaccines substantially reduced disease transmission.

"What we found goes against much of what is currently suspected about pertussis resurgence," Pejman Rohani, a population ecologist and epidemiologist at the university, said. "It's not difficult for us epidemiologists to propose some possible mechanism behind the resurgence, but what's been missing so far is an effort to challenge each of these hypotheses to explain the data. That's exactly what we did."

The research team tested multiple hypotheses for the resurgence of pertussis in mathematical terms and used statistical analysis to test how well the transmission models explained the data in Thailand. The most effective fit came from a model that assumed lifelong immunity after naturally acquired infection or vaccination. The team found no evidence of a pertussis resurgence in Thailand.

"We found very few cases overall, and especially in infants," Julie Blackwood, the lead author of the study, said. "So the big underlying finding is that the vaccine is adequately protecting infants from contracting the infection."

Thailand mainly uses a whole-cell vaccine while the U.S. uses an acellular vaccine. The two countries also have slight variations in their vaccination schedules.

Pertussis, also known as whooping cough, is a highly infectious respiratory disease that causes approximately 300,000 deaths worldwide annually, primarily among infants in the developing world.

The team published its findings in Monday's edition of the Proceedings of the National Academy of Sciences.