THURSDAY, SEPTEMBER 29, 2016

Study: Whole-cell vaccines more effective for pertussis than acellular

Whole-cell pertussis vaccines were more effective against the disease also known as whooping cough than acellular vaccines during a recent outbreak in California, according to a recent Kaiser Permanente study.

The study examined 10- to 17-year-olds who received pertussis vaccines during the 2010-2011 California pertussis outbreak. The researchers evaluated the risk of pertussis during the outbreak related to how many whole-cell and/or acellular pertussis vaccines the participants received as toddlers and infants. Kaiser Permanente announced the results of the study on Monday after it was published in Pediatrics.

"Studies have suggested that protection following the acellular pertussis vaccine is less enduring than following the whole-cell pertussis vaccine," Nicola Klein, the lead author of the study, said. "Although reasons for the recurrent pertussis outbreaks are complex, waning protection following five doses of acellular pertussis vaccine plays a central role, at least in recent epidemics."

The study found that individuals had a 40 percent higher risk of pertussis for each acellular pertussis vaccine dose received as compared to receiving a whole-cell vaccine between the ages of one month and 24 months. Teenagers who received four doses of the acellular vaccine had nearly a six time higher risk of contracting pertussis than teenagers who received four doses of the whole-cell vaccine.

Subjects who received a mix of whole-cell and acellular vaccines were approximately four times more likely to contract pertussis than subjects who received only the whole-cell pertussis vaccine.

Whole-cell pertussis vaccines were available from the 1940s to the 1990s. They were replaced with acellular pertussis vaccines because of safety concerns with the whole-cell vaccines. The U.S. switched over from whole-cell to acellular vaccines by the late 1990s.

Previous studies found that a fifth booster dose of acellular pertussis vaccine did not overcome the advantage in protection from four doses of the whole-cell vaccine.

"The results indicate that a booster dose of Tdap does not overcome the advantage in protection from pertussis afforded to those who previously received four doses of the whole-cell vaccine," Klein said. "Despite this, boosting the newly emerging cohort of acellular pertussis vaccine-only teenagers with Tdap remains the best means currently available to help protect this group against disease."