December 19, 2003

Deadly pertussis focus of VCH study

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Dr. Natasha Halasa

Deadly pertussis focus of VCH study

Vanderbilt Children’s Hospital researchers are alarmed that four children died in Tennessee over the last year from pertussis, or whooping cough.

Dr. Natasha Halasa, clinical fellow, Pediatric Infectious Diseases and Dr. Kathryn Edwards, vice chair of Clinical Research and professor of Pediatrics have published an editorial in November’s The Journal of Pediatrics encouraging a change in the immunization schedule to better protect very young babies from the bacterial infection.

Halasa is also the first author of a study in Pediatrics, the publication of the American Academy of Pediatrics, reviewing the effectiveness of extreme lifesaving techniques to save babies who have gone into respiratory failure because of pertussis.

Pertussis is a bacterial respiratory infection caused by Bordetella pertussis bacteria. It causes a severe cough that can literally take your breath away, and it lasts for many weeks. It is often referred to the “100-day cough.” But while the disease is little more than an annoyance in older children and adults, it can be a killer for infants, particularly those who have not yet begun their series of vaccinations. The series of 5 shots begins at two months of age and is administered at 4 months, 6 months, 15-18 months, and 4-6 years of age.

“Adolescents and adults are no longer protected by their childhood vaccines due to waning immunity,” said Halasa. “One in every five people who have a cough greater than two weeks may have pertussis.”

It’s that relatively high incidence of pertussis in older children and adults that leaves very young babies at risk, especially if a parent or sibling has a lingering cough.

Gracelyn Mansfield will turn 2 on New Year’s Day, but she nearly died when she was just five weeks old because of pertussis, an illness her parents and surprisingly even her doctor, knew little about.

“You hear about whooping cough because of the vaccine,” said Gracelyn’s father Brian Mansfield. “But you never get diagnosed with it.”

Gracelyn’s cough concerned her parents, but the doctor told them it was viral and that nothing could be done, except to wait it out. No one suspected her life might be in danger.

“It was Feb. 13, the day before Valentine’s Day. I had just changed Gracelyn’s clothes,” recalled her mother, Nancy Mansfield. “I picked her up, cleared her nose then she coughed and coughed and couldn’t get her breath. I sat down with her in the rocking chair, and she just went limp. I yelled to Brian to call 911 that Gracelyn had stopped breathing.”

The Mansfields were guided by a 911 operator to give the baby rescue breaths over the course of just a few minutes, but to the family it seemed like hours before the ambulance arrived.

“She had already turned gray. The operator told me to cover both her mouth and nose when I breathed for her, so I did,” said Jennifer, “and on the first breath she gurgled a bit, then on the second breath she started crying.”

Gracelyn spent a week at Vanderbilt Children’s under an oxygen tent as she recovered from pertussis. The whole experience was traumatic but it was even more disturbing later to find out that a lingering cough both parents had in the weeks before Gracelyn got sick was likely pertussis, and that they had probably passed the illness to their baby.

But the Mansfields were lucky. In the year that followed Gracelyn’s illness, four babies, all under the age of 3 months who were referred to Vanderbilt Children’s Hospital, died from pertussis. All had developed intractable pulmonary hypertension.

“We don’t know exactly why this happens,” Halasa said of the deaths. “It could be the pressure gets so high in the pulmonary artery that babies cannot survive.”

Halasa’s study in December’s Pediatrics found even more disturbing information that even the most advanced treatments for respiratory illness don’t appear to work effectively for infants with pertussis.

Nitric oxide or NO treatment is used to improve the exchange of oxygen in the lungs by dilating the pulmonary arteries, and extracorporeal membrane oxygenation, or ECMO, is much like using a heart-lung bypass machine. Tubes remove the baby’s blood from a tube in the neck, oxygenate it, and then return it to the heart. Both ECMO and NO are very high-level treatments for babies whose lungs are failing because of infection, injury or disease.

“Many babies under 3 months survive with NO and ECMO,” said Halasa. “But not the kids with pertussis.”

Halasa, Edwards, and other VCH researchers, looked at a very complete international database of the thousands of kids who use ECMO every year.

“And in one time period there were around 30 kids who used ECMO who had pertussis,” said Halasa. “During this 1999-2001 time period it represented 1 percent of all ECMO cases. In the earlier time period of 1990-1992, only 0.1 percent of the ECMO cases were due to pertussis. The death rate for those kids on ECMO was 70 percent, and even 80 percent at less than 6 weeks. Death rates are usually much lower when compared to infants with persistent pulmonary hypertension of the newborn.”

The answer, Halasa said, is clearly prevention with a new immunization schedule.

“I think several strategies would be good to try,” said Halasa. “Pregnant mothers given the vaccine may pass some protection on to babies, adolescent boosters would reduce the chances of adolescents or adults giving it to babies, but we’re about to study how effective it would be to give a baby’s first pertussis vaccination earlier in life — at birth.”

Right now Halasa is looking to enroll 50 women who are preparing to deliver full term babies or healthy infants between the ages 2-14 days who have not yet received their Hepatitis B vaccination. In this pilot study, 25 newborns will get the normal Hepatitis B vaccine at birth, while the other 25 will get a diphtheria, tetanus and acellular pertussis (DTaP) vaccination along with their Hepatitis B vaccine; That’s two months before the normal schedule to begin vaccination for pertussis.

The main purpose of this study is to determine if babies can mount an adequate immune response at birth and that this approach does not cause more side effects than the usual vaccination schedule. If it is successful, Halasa hopes an eventual change in the immunization schedule might save babies’ lives.

For more information on the study, email or call Alice O’Shea at 343-8518.