As debate simmers about whether parents should be forced to vaccinate their children, California’s whooping cough outbreak underscores a disturbing truth about the current version of the pertussis vaccine: It is wearing off after just a few years, and many Californians who thought they were protected instead are catching the disease.
As debate simmers nationwide about whether parents should be forced to vaccinate their children, Elk Grove residents have made their choice: Only 80 of the suburb’s 4,500 kindergartners opted out of vaccinations last year, state data show.
Despite those precautions, whooping cough ripped through Elk Grove’s classrooms and cul-de-sacs in 2014. Infection rates within the large Sacramento suburb were three to five times higher than rates elsewhere in the county, local health records show.
The paradox – high infection rates amid high immunization rates – underscores a disturbing truth about the current whooping cough vaccine: It is wearing off after just a few years, and many Californians who thought they were protected instead are catching the disease.
“Children who were vaccinated did not receive the protection desired,” said Kate McAuley, program coordinator of communicable disease and immunization at the Sacramento County Public Health Department. “We had many high-school-aged children who had pertussis. They had received vaccines. The vaccine is lasting two to three years.”
Several of California’s leading infectious disease specialists expressed similar concerns. “This newer version of the vaccine probably has a shorter period of protection. I think that is a scientifically proven point,” said Dr. Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children’s Hospital.
Also called pertussis, whooping cough can be marked by fatigue, vomiting and a distinctive “whoop” sound made by sufferers trying to get a breath after a severe coughing fit. It’s especially dangerous to infants; four babies died from pertussis in California last year.
Whooping cough was a menace in California until the 1940s, when a vaccine was developed. That earlier version was remarkably effective, lowering the number of whooping cough cases in California from thousands a year to dozens.
The early vaccine contained whole, dead pertussis bacteria. It worked well, but in a very small percentage of children caused extreme reactions, including high fever and seizures. Concerned about potential side effects, many parents refused to let their children get inoculated.
In response, vaccine makers in the late 1990s introduced shots that contained only pieces of pertussis bacteria. The new regimen called for five doses by age 6, and a booster shot by 12. The serious adverse reactions dropped significantly – but at a price.
With the new shots, “You get protection in the first year; every year after that, the protection rate drops 10 percent or so,” Blumberg said.
A recent study in the Journal of the American Medical Association confirms the limitations: Researchers found that the new vaccine provides solid protection in the first year but that the effectiveness steadily declines over five years, often leaving children vulnerable before they get their booster shot. Adults are also vulnerable if several years have passed since the booster inoculation.
The state requires schoolchildren to be vaccinated against pertussis, as well as measles, mumps and several other diseases, before they start kindergarten. Thousands of parents file “personal belief” exemptions each year and leave their children unvaccinated.
As with the measles outbreak sweeping California, parents of unvaccinated children have taken most of the public blame for recent whooping cough epidemics. But the connection between who gets shots and who gets sick isn’t as strong with pertussis as it is with diseases such as measles.
“It’s an outlier,” said Dr. Mark Sawyer, a professor of pediatrics at the University of California, San Diego, and a member of the U.S. Centers for Disease Control and Prevention immunization practices committee.
A map of Sacramento County illustrates the unlikely pattern: About 440 Sacramento County residents had either confirmed or probable cases of whooping cough last year, and roughly half of those with confirmed cases lived in or around Elk Grove. The suburb of North Highland, on the other hand, had among the highest rates of parents opting out of vaccinating their children but reported fewer than five pertussis cases last year.
Statewide, a record-high 11,000 Californians caught whooping cough in 2014. About 4,500 of them lived in counties where fewer than 2 percent of kindergartners opted out of vaccines last year.
“It’s not correct to only pin (the pertussis outbreak) on the people who are unvaccinated,” Sawyer said. “The effectiveness of the vaccine is a huge part of this. People who are immunized do still get pertussis.”
Even so, McAuley, Blumberg and other doctors said it was critical that parents vaccinate their children against pertussis, noting that the vaccine still reduces the chances of infection.
A 2013 study in the journal Pediatrics found a significant correlation between low vaccination rates in California and high rates of pertussis. Unvaccinated children and adults, the experts noted, are still more likely to catch the disease and put others at risk.
“People shouldn’t avoid this vaccine for any reason,” Sawyer said.
Mill Valley parent Joan Bullen became aware of the vaccine’s limitations in December 2013 when her high-school-age daughter, Emma, caught pertussis years after vaccination. Bullen was frustrated and surprised.
“We were aware that kids were getting it, but we thought we didn’t have to worry,” she said. “The cough was just hellish for weeks and weeks and weeks. She couldn’t sleep at night.”
Emma eventually recovered, even as whooping cough swept through her school. “There were so many kids who had it and didn’t know they had it,” Bullen said.
The same type of story played out repeatedly in Elk Grove, county public records show.
In the 95758 ZIP code surrounding the Laguna community of Elk Grove, residents caught pertussis last year at a rate three times as high as residents elsewhere in Sacramento County. Parents of just six of the 430 kindergartners in that ZIP code filed personal-belief exemptions this school year, opting not to vaccinate their children. And just seven of the 500 seventh-graders opted out of the booster shot.
“We were surprised by the increase in cases last year,” Elk Grove Unified spokeswoman Xanthi Pinkerton said in an emailed statement. “We do have a high percentage of students who have been immunized.”
The district responded by disseminating common-sense advice, encouraging children to practice good hygiene.
Dr. Scott Cannon practices family medicine at a Sutter Health clinic in the Laguna community. A strong advocate of vaccinations, he recently has treated “a handful” of whooping cough patients. Most were adults who had been vaccinated against the disease, but years had passed since their last shot.
Dr. John Belko, a pediatric infectious disease specialist at the Kaiser Elk Grove Promenade medical office, said about a third of the pertussis cases treated in his practice in 2014 involved unvaccinated patients, a third involved patients who didn’t get the full regimen of shots, and a third were patients whose vaccine had worn off.
“I think we did a better job of testing and identifying” pertussis cases than clinics elsewhere, he said, offering another explanation why so many cases were reported in Elk Grove.
A few labs are working on pertussis vaccines that provide longer-lasting protection, but it could be years before those efforts produce results, several experts said.
In response, doctors have begun encouraging adults to get a pertussis booster if it has been more than a decade since their last shot. Physicians also now urge adults who spend time around infants to get a booster, since the disease can be devastating to babies.
Doctors also try to manage the disease through quick diagnosis and community outreach when an outbreak hits. Their efforts are hampered by the fact that some whooping cough cases are mild and patients don’t seek help. Even with a record high number of pertussis cases reported last year, thousands more likely went unreported, several health experts said.
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