BETHESDA, Md. Yet another acellular pertussis vaccine has proven safe and effective for primary immunizations, concluded the Food and Drug Administration's (FDA) Vaccines & Related Biological Products Advisory Committee.
The FDA committee recently agreed the diphtheria-tetanus-acellular pertussis (DTaP) vaccine (Acel-Imune, Wyeth-Lederle Vaccines and Pediatrics) is safe and effective when given to children at 2 months, 4 months, 6 months and 18 months of age. The FDA committee also concluded the acellular pertussis vaccine will be safe and effective when administered concurrently with other vaccines recommended for infants, such as Haemophilus influenzae type b (Hib), hepatitis B and oral polio vaccines (OPV).
The committee, however, did express differing opinions concerning the need for additional safety and efficacy data to support the fifth dose following four doses of DTaP.
Acel-Imune originally received approval for its acellular pertussis vaccine in 1991 for use in booster doses at ages 18 months and 5 years after three doses of whole-cell pertussis vaccine.
The four-antigen acellular pertussis vaccine includes agglutinogens (FIM), pertactin (PRN), filamentous hemagglutinin (FHA) and inactivated pertussis toxin (PT).
The efficacy rates are lower for the acellular vaccine than for the whole-cell vaccine, but with fewer adverse effects, according to study results.
In the Lederle safety trials, 6,941 children received 20,390 primary series doses, 5,125 received the fourth dose and 357 received the fifth dose. At the first and fourth doses, erythema was experience by fewer children in the acellular group than in the whole-cell group. At the first dose, 5% of acellular vaccinated children had a fever of over 38° C, compared to 45% for whole-cell vaccinated children. By the fourth dose, 25% of those vaccinated with acellular pertussis vaccine had fevers compared to 50% of those receiving whole-cell vaccines.
The study shows children receiving acellular vaccine also experienced less drowsiness (20%) at the first dose than the whole-cell group (35%). Persistent crying was significantly lower with the acellular vaccine, occurring in only three infants out of 4,273 doses. Out of 4,259 doses of the whole-cell vaccine, 43 infants reportedly suffered from persistent crying.
Frequency of reactions with acellular increased with each subsequent dose, but always remained lower than with whole-cell. The committee gave this as a reason for possibly requesting more information on the fifth dose.
Lederle altered the licensed Acel-Imune formulation for the infant immunization by increasing the aluminum concentration from 0.15 mg/dose to 0.23 mg/dose to increase the adjuvant effect, because the adjuvant effect which was absent in the whole-cell vaccine.
The efficacy and immunogenicity results submitted to the committee were based on use of the new formulation. The acellular pertussis safety database includes administration of both the old and the new formulations.
The committee is expected to review the additional data and make a decision at a later date.
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