(RxWiki News) Vaccines may be the most important disease prevention tool that science has ever seen. But they aren't without their hiccups.
At least that's the main finding of a new study that explored the 2010 and 2014 whooping cough outbreaks in California.
In this study, researchers from Kaiser Permanente found — although the Tdap booster vaccine protected against pertussis (whooping cough) in the first year after vaccination — its effectiveness declined to less than 9 percent after four years in teens who were given a newer form of the shot as babies and children.
Researchers said understanding exactly why the vaccine failed is a matter of some urgency when considering that an estimated 16 million cases of whooping cough occur worldwide each year. Whooping cough also resulted in an estimated 195,000 deaths in 2014 alone, according to the Centers for Disease Control and Prevention (CDC).
Whooping cough is a highly contagious respiratory disease that causes a severe hacking cough that can last up to 10 weeks. It is especially serious for babies and young children.
During the 1990s, the US switched from the whole cell pertussis (DTwP) vaccine to the acellular pertussis (DTaP) vaccine. The DTaP vaccine is currently used for all children ages 2 months to 6 years. The vaccine protects babies and children against whooping cough, diphtheria and tetanus.
Although DTaP was widely used, the US and other countries experienced a surge in whooping cough cases in the years after switching vaccines. In 2006, the Advisory Committee on Immunization Practices recommended a booster acellular pertussis (Tdap) vaccine for adolescents ages 11 to 12.
This study looked at the effectiveness of the Tdap vaccine among adolescents during the 2010 and 2014 whooping cough outbreaks in Northern California.
Researchers found that routine vaccination at ages 11 and 12 did not prevent the outbreaks. Although more than 90 percent of teens had received the Tdap booster, they had the highest rate of whooping cough out of any age group in 2014.
"This study demonstrates that despite high rates of Tdap vaccination, the growing number of adolescents who have received only the newer acellular pertussis vaccines continue to be at higher risk of contracting whooping cough and sustaining epidemics," said lead study author Nicola Klein, MD, PhD, in a press release. Dr. Klein is the co-director of the Kaiser Permanente Vaccine Center.
She continued, "Because Tdap provides reasonable short-term protection, it may contain whooping cough more effectively if it is administered to adolescents in anticipation of a local outbreak rather than on a routine basis at age 11 or 12."
This study was published Feb. 5 in the journal Pediatrics.
Kaiser Permanente funded this research.
The pertussis vaccines in this study were manufactured by GlaxoSmithKline and Sanofi Pasteur, both of which provided funding for this study.