Why Didn’t the Whooping Cough Vaccines Work?

Tdap vaccine booster loses effectiveness among adolescents, according to Kaiser Permanente investigation


Some vaccines require additional booster shots later on down the road, to keep patients protected from a disease.

New research explains why additional booster shots were given to kids in California after a whooping cough outbreak in 2010, and why the shots failed.

According to a news article issued by the Los Angeles Times, 10- and 11-year-olds in California were hit hard by the pertussis (whooping cough) outbreak in 2010, though the children had received five doses of whooping cough vaccine before they were six. Thinking that the vaccine must lose its effectiveness, public health officials started requiring booster shots for students entering seventh grade.

In 2014, California experienced another whooping cough outbreak, and 10- and 11-year-olds were hit hard again. The group hit hardest this time was the 14- to 16-year-olds, the same ones who received the booster entering seventh grade.

Researchers at Kaiser Permanente Vaccine Study Center decided to investigate.

According to a press release issued by Kaiser Permanente, the explanation is two-fold. Kaiser researchers conducted a study that showed that Tdap—the booster vaccine given before seventh grade—only provided moderate protection for about a year. Its effectiveness dropped below 9 percent after about 4 years.

"I think we were hoping the Tdap booster would counteract what happened in 2010," lead study author Nicola Klein, MD, PhD, and co-director of the Kaiser Permanente Vaccine Study Center told the Times. "Unfortunately, it didn't. It worked pretty well for about a year and unfortunately it doesn't work well after that."

According to the Times, the U.S. started using an acellular vaccine for whooping cough in the 1990s, called DTaP, which one Kaiser study found lost about 42 percent of its effectiveness each year. Previously, the U.S. administered a whole cell vaccine called DTwP, which had a longer protection period. The U.S. stopped using it because it sometimes caused convulsions and fever in small children.

As a result, the Tdap booster was recommended for children who had received the acellular vaccine DTaP. According to the Kaiser Permanente press release, Dr. Klein says that instead of administering the booster at a certain age, it may be more effective to use it when expecting an outbreak.

"The strategy of routinely vaccinating adolescents to prevent future disease did not prevent the 2014 epidemic, arguably because the protection afforded by a dose of Tdap was too short-lived," says Dr. Klein in the Kaiser press release."While awaiting development of new vaccines that will provide longer-lasting protection against pertussis, we should consider alternate Tdap immunization strategies for adolescents."

Dr. Klein and colleagues’ study was published February 5 in Pediatrics. It was funded by Kaiser Permanente.

Two of the study’s authors present possible conflicts of interest and state that the pertussis vaccines they studied were manufactured by GlaxoSmithKline and Sanofi Pasteur, both of which funded research.