U.S. DPT vaccine trial looks good.

U.S. DPT vaccine trials look good

The combination vaccine against diphtheria, pertussis and tetanus (DPT) protects children against these killers, but the pertussis part of the triad has created its own victims -- a small proportion of vaccinated children who develop permanent neurological impairment. The first details of U.S. trials of a new pertussis formulation developed in Japan have just been released. They indicate that the new vaccine, which has already done well in Japan and Sweden, may be safer.

The current vaccine is made of whole, killed cells of Bordetella pertussis bacteria. Side effects range from a few days of pain, swelling and fever to, in rare instances, lasting brain damage. The Japanese vaccine uses two partially purified proteins from the bacteria.

Two studies in the September AMERICAN JOURNAL OF DISEASES OF CHILDREN describe the use of the Japanese vaccine in U.S. children. At the University of California at Los Angeles, researchers compared reactions among 18- to 24-month-old children receiving their fourth DPT booster. Forty children got the new vaccine and 20 got the current one. The new vaccine caused significantly fewer side effects. For example, while 85 percent of the children receiving the current vaccine developed a fever, only 5 percent of the others did. The injection site was tender in all of the current-vaccine recipients, compared with 22.5 percent of the new-vaccine recipients.

In the second study, done at Vanderbilt University in Nashville, Tenn., 20 children aged 4 to 6 years and 20 toddlers aged 18 to 24 months were given DPT boosters made with the two proteins, and an equal number got the currently used shots. As in the UCLA study, the new and old vaccines boosted pertussis antibodies in approximately equal measures, and side effects with the new vaccine were significantly rarer than with the old one.

The studies, both groups note, are not definitive. Both were too small to indicate whether the more severe neurological complications are less likely with the new vaccine, and all subjects had received previous vaccinations without adverse reaction. Comments Alan Hinman, an immunization expert at the Centers for Disease Control (CDC) in Atlanta, "The results are encouraging but we're particularly interested in seeing results of vaccination in children younger than those in these studies." Hinman and a CDC colleague have estimated that 51 U.S. children a year suffer permanent brain damage from the current vaccine.