The vaccine for whooping cough loses effectiveness over time and may explain the recent outbreaks of the highly contagious bacterial infection, a new study reports.
More than four out of five confirmed whooping cough - pertussis - cases strike children who are fully vaccinated, the study authors said, highlighting the need for new vaccines to protect children from the highly contagious disease, according to CNN.
Up to age 7, kids have a five times higher whooping cough risk when they're three years out from their last shot, compared to the year immediately after vaccination, according to the report published online June 10 in Pediatrics.
The findings showed that children between 7 and 11 have double the risk if they are more than six years away from their last shot, compared with less than three years after. "We found children who received their vaccines and who are far away from their last vaccine were at increased risk of pertussis [whooping cough]," said lead researcher Ousseny Zerbo, from the Vaccine Study Center at Kaiser Permanente Northern California in Oakland. "As time goes by, the effectiveness starts to wane."
However, researchers did not fail to point out that the vaccine remains a vital means of preventing the disease. Risk of catching whooping cough is 13 times higher among unvaccinated children and twice as likely among kids who are behind on their shots, compared with fully vaccinated kids, the study authors said.
According to Dr. Kathryn Edwards, a professor of pediatrics at Vanderbilt University who was not involved in the study, health care organizations and the CDC must "continue to monitor the pertussis burden in the United States and work with scientists to improve the existing pertussis vaccines."
Edwards added that the research is ongoing, and one of the techniques currently being studied involves increasing the number of antigens -- the bits of B. pertussis cells that are recognized by the immune system -- to better mimic the older whole-cell vaccines. According to CNN, another technique involves the use of living, but weakened, bacteria injected into the nose.