Healther Petersons listened to her five-year-old daughter, Camille, and worried.
“She would cough and cough and cough and then she would be gasping to take a breath,” Petersons recalled. “Her eyes would be watering from coughing. The coughing wiped her out.”
But April 2012 was a busy time for the Milwaukee family, and it was probably just a bad cold. Camille kept going to her kindergarten class at St. Dominic Catholic School. The family held an adoption party for her new younger sister and invited about 20 people. All the while, Camille could not shake her cough.
It got so bad Petersons videotaped her daughter before heading to the family doctor, just in case the child stopped coughing the moment they entered the exam room.
The doctor took a swab for testing and called back a few hours later. Camille had pertussis, whooping cough. She had caught the disease even though she’d been vaccinated against it.
The whole family had to go on antibiotics. So did all the guests from the adoption party, although ultimately none came down with the illness.
“We felt horrible that we’d (possibly) infected all of these people without knowing because we thought she had a bad cold,” Petersons said. “I remember thinking whooping cough was one of those old-school things that nobody got anymore.”
Pertussis, known for an explosive cough so violent it can break a person’s rib or cause the person to vomit or pass out, had appeared to be on the way out in the US in 1976, the disease’s low ebb.
There were just 1,010 cases – far below the 100,000 typical in the 1940s. The disease was vanishing under the assault of childhood vaccinations.
Not anymore. The year Camille got pertussis, Wisconsin alone recorded 6,462 cases. The national total was 48,277.
Experts and research point to a complex confluence of factors that may have caused the surge in cases, including: a safer but weakened vaccine; more surveillance, especially in adults; genetic changes to the bacterium; and a proliferation of wary parents and anti-vaccine websites.
And then there is the disease itself, with its remarkable capacity to spread. Each case of Ebola is estimated to generate 1.5 to two more cases; each smallpox case, six to seven more.
A single case of whooping cough, however, generates anywhere from 12 to 17 more. And every three to five years, there is a major outbreak and the numbers spike.
“This is a very tenacious disease,” said Paul Biedrzycki, Milwaukee’s director of disease control and environmental health. “It’s a very challenging disease for public health. Recovery between outbreaks is getting shorter and slower. It’s simmering, which tells me our control strategies may not be working.”
“What makes pertussis a difficult foe is that there isn’t one, simple explanation (for the resurgence),” said Pejman Rohani, a University of Michigan epidemiology professor who has studied the disease for 17 years. “I think there’s a lot we don’t understand about what’s been going on.”
The story of pertussis in the 20th and early 21st centuries has been influenced by the evolution of the vaccines that have been developed to fight it. In the pre-vaccine years of 1926 to 1930, there were more than 36,000 pertussis deaths in the US, according to a 2007 paper on the history of the disease.
In 1948, the first widely used vaccine was introduced; it was made by killing the pertussis bacterium with an antiseptic and injecting it into the body.
The whole-cell vaccine, as it came to be called, was loaded with several thousand proteins, including toxins, that fired up the immune system and clamped down on the disease.
In the decades that followed, whooping cough deaths and cases dropped dramatically. But the vaccine also caused side effects, including pain at the injection site, fevers and persistent crying in some children, and in rare cases seizures.
The 1982 NBC News documentary DPT: Vaccine Roulette went further, claiming the pertussis vaccine could cause permanent brain damage, said Paul Offit, director of the Vaccine Education Center and a professor of paediatrics in the division of infectious diseases at the Children’s Hospital of Philadelphia.
“It cast a negative light on the whooping cough vaccine,” said Offit, author of Deadly Choices: How the Anti-Vaccine Movement Threatens Us All. “Even physicians didn’t understand that it didn’t cause permanent brain damage.”
A 1990 study in The Journal of the American Medical Association found no evidence that the vaccine caused brain damage. Nonetheless, concern over the side effects led to development of a new pertussis vaccine made from components of the bacterium rather than the whole cell.
This kinder, gentler acellular vaccine, introduced in 1998, causes fewer side effects than the old vaccine, but appears to be less effective.
“It does work,” said Nicola Klein, a paediatrician and co-director of the Kaiser Permanente Vaccine Study Center. “It just doesn’t last long.”
Klein was the lead author of a 2013 study in the journal Pediatrics comparing the effectiveness of the older and newer vaccines in a 2010-2011 pertussis outbreak in California. It showed that teenagers who got four doses of the newer vaccine were nearly six times more likely to get pertussis than teens who got four doses of the older vaccine.
Other developments suggest the change in vaccines may not be fueling the resurgence. Japan and Sweden have been using the same acellular vaccine as the US.
“They’ve seen a real reduction in pertussis and there’s been no sign, as far as we can tell, of a pertussis resurgence,” said Rohani at the University of Michigan.
Sweden does use a different schedule for pertussis shots, administering the first three when babies are three, five and 11 months old. In the US, the first three pertussis shots are given at ages two, four and six months, followed by one between 15 and 18 months, and a fifth and final shot between four and six years.
Another possible explanation offered for the rise in whooping cough in the US is a greater awareness of the disease among adults.
While there had long been a keen awareness of the disease in children, there had been less awareness that it strikes adults, said Michael Chusid, a doctor and professor of pediatric infectious disease at Children’s Hospital and the Medical College of Wisconsin. That has changed in the last decade or so, and the additional adult pertussis patients may now account for some of the disease’s resurgence.
“These cases were probably always there,” Chusid said, explaining that it was easy to miss them because the disease doesn’t tend to be as severe in adults as it is in children.
Not only has the vaccine changed, but so apparently has its target.
“There are genetic changes in (what) is circulating now compared to the bacterium that was circulating awhile back,” Rohani said. “We don’t know what that evolution means in terms of transmission.”
Despite the changes in the vaccine and in the bacterium, public health officials believe vaccinating children against the disease is critical.
They worry that critics and anti-vaccine websites may discourage parents from ensuring their children receive the shots. A growing number of parents have sought waivers allowing them to forgo vaccinating their children.
In states such as California, waivers can lead to 10% to 20% of children, or more, not being vaccinated, Offit said.
In Wisconsin, waivers to school immunisations can be granted for religious, personal or medical reasons. Waivers were granted for about 5% of kindergarten through 12th-graders in Wisconsin for the 2013-2014 school year, according to data supplied by the state.
That’s up from 2.3% in 2000-2001.
Even those, like Camille Petersons, who still get whooping cough after being vaccinated, are much more likely to have a milder case than if they had not been vaccinated at all, said James Cherry, a paediatric infectious disease expert at the UCLA School of Medicine.
“You are going to have more failures, but the failures are going to be less ill,” he said.
Several experts said a more effective whooping cough vaccine is needed, but it is unclear when one might be developed. – Milwaukee Journal Sentinel/Tribune News Service