New approaches considered to combat rise in pertussis

Washington -- In recent years, the number of U.S. cases of pertussis has increased.

This troubling trend appears to be continuing, with several states reporting outbreaks that some public health officials expect will last through the summer. Cases have been reported in Illinois, Nebraska, New York and Wisconsin, and pertussis is suspected in the death of a Montana infant.

So far this year there have been about 1½ times the number of cases in Milwaukee as there were last year at this time, said Bevan K. Baker, the city's acting health commissioner. Milwaukee County has 57 confirmed cases, and the city has another 37. "We are probably approaching the 200 mark in terms of regional and state cases."

The health department is tracking 3,000 contacts to prevent further spread, a daunting task but one for which the agency has prepared.

"We didn't just turn on the light on this. This is what we do day in and day out," said Baker.

Meanwhile, he is preparing for a long siege. "We may be just on the upload of the curve, and have to ride the crest of the wave through the summer," he said.

The increase in pertussis cases poses the greatest peril to infants younger than 6 months, said Kathryn Edwards, MD, professor of pediatrics at Vanderbilt University in Nashville. The severe coughing that accompanies the illness can lead to the inability to eat, and infants with pertussis are much more susceptible to pneumonia and sleep apnea, she said.

Infants can contract the disease from older siblings or even their own parents who may have a mild case that has gone unrecognized. Although the pertussis vaccine is effective soon after it is administered, beginning at 2 months of age, its effectiveness wanes over the years.

Routes to protection

With this in mind, researchers are exploring ways to protect infants by either providing them with very early protection or by surrounding them with people who have been recently vaccinated against the disease.

Researchers at Vanderbilt are conducting a pilot study in which 25 infants will be given a pertussis shot during their first two weeks of life. Another 25 infants will begin the series of shots at the usual 2 months.

"We will be looking at whether by giving an earlier dose we can speed up the process of immunity and hopefully circumvent the problems and provide a little protection," Dr. Edwards said.

A vaccine suitable for teenagers and adults could provide another route to protection, she said. "The tea leaves are telling us there will be at least one pharmaceutical company making an application to the Food and Drug Administration within the next year for an adolescent vaccine."

Inoculating teens and young adults who come into contact with infants would provide a "cocoon" of protection for the infants, thus shielding them.

A third approach under discussion is the immunization of mothers before they give birth. The thought is that antibodies would be transferred via the placenta to their babies. "This one is just on the drawing board," said Dr. Edwards.

A vaccine for teens is now being offered in Canada, but not very many of them have taken advantage of it, she said. "But, often it takes time for people to get used to something new."