WASHINGTON — The safety profile of Aventis Pasteur's reduced-antigen tetanus-diphtheria-acellular pertussis vaccine in adolescents is similar to that of the currently-licensed tetanus-diphtheria vaccine, Michael E. Pichichero, M.D., reported in a poster presentation at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
Aventis Pasteur's reduced-antigen tetanus-diphtheria- acellular pertussis (Tdap) vaccine, called Adacel, has been licensed in Canada for booster immunization of adolescents and adults. It is under review by the Food and Drug Administration for use in individuals aged 11-64 years.
Two randomized multicenter U.S. trials included 2,990 adolescents aged 11-17 given Tdap and 792 given tetanus-diphtheria toxoid (Td), said Dr. Pichichero, a specialist in pediatric infectious diseases who practices in Rochester, N.Y.
Immediate reactions (within 30 minutes) were reported at comparably low frequencies in both the Tdap and Td groups (0.5%-0.6%). Most reactions were mild and resolved within a day. Also comparable were the frequency, intensity, and mean duration of fever of 38° C or greater (seen in 5.0%-5.2% with Tdap, 2.7% with Td) and injection site erythema and/or swelling (20.8%-24.3% with Tdap, 18.3%-19.7% with Td).
Pain at the injection site was slightly but significantly more frequent in the Tdap group (79.2% vs. 71.0%), but this pain was usually of mild intensity and its mean duration did not differ significantly between the two groups, Dr. Pichichero said at the conference, sponsored by the American Society for Microbiology.
Postvaccination limb circumference measurements within 2 weeks of vaccination were very similar between the two groups (increases of more than 3 cm occurred in roughly 5% of each group), and no study subjects had whole arm swelling. Headache, generalized body ache, and tiredness (mostly mild) were the three most commonly reported solicited systemic events, all in less than 30% of each group.
Unsolicited events such as pharyngitis, nasopharyngitis, and cough within 28 days of vaccination were reported with equal frequency, intensity, and type between the two groups. Most were mild or moderate and not related to vaccination. Serious events were rare (1% or less in both groups), comparable in frequency, and unrelated to vaccination, he said.