December 1996
ATLANTA — The Advisory Committee on Immunization Practices (ACIP) is putting the finishing touches on its recommendations for using acellular pertussis vaccines for the primary series.
The recommendations will state a preference for the diphtheria-tetanus-acellular pertussis (DTaP) formulations for the infant doses at 2 months, 4 months and 6 months of age. Previous recommendations had stated a preference for acellular vaccines for the fourth and fifth doses.
The revised recommendations will also state that diphtheria-tetanus-whole cell pertussis (DTP) vaccines are acceptable alternatives.
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Until the Food and Drug Administration licensed the first DTaP vaccine (Tripedia, Connaught) for the primary series, acellular pertussis vaccines could only be used for the two booster doses at 15 months to 18 months and at 4 to 6 years of age. Several other DTaP vaccines are awaiting FDA approval.
Because data were lacking on the fifth dose of DTaP among children who had received four previous doses of acellular vaccine, the FDA approved the product only for the first four doses. It is approved for the fifth dose in children who have received the whole-cell vaccine for one or more of the primary doses.
Committee members noted, however, that it will be at least four years until children who have been primed with DTaP will be ready for the fifth dose. In the interval, data will continue to be collected regarding the safety and efficacy of five doses of the acellular vaccines.
"The FDA has not approved Tripedia as the fifth dose among persons who have received only acellular vaccine for the first four doses in the vaccination series because data of this fifth dose are insufficient to date," the draft recommendations noted. "However, such data should be available before infants vaccinated according to the revised vaccination schedule require a fifth dose at 4 to 6 years of age."
The National Institute of Allergy and Infectious Diseases (NIAID) is conducting follow-up studies on children who had been included in the original acellular pertussis vaccine trials, said Regina Rabinovich, MD, chief, clinical studies section, division of microbiology and infectious diseases, NIAID. She is a liaison representative to the ACIP.
The NIAID study has been able to conclude that five doses of DTaP are associated with fewer injection site reactions and lower rates of fever and irritability compared with whole-cell vaccines.
When used as the second booster dose among children who had received four prior doses of DTaP, all acellular pertussis vaccines showed a trend toward increasing swelling and pain at the injection site, Rabinovich said.
"Five doses of acellular pertussis vaccines produce fewer of all types of local reactions than five doses of whole-cell vaccine, but those receiving all DTaP may have local reactions with the booster doses," Rabinovich said.
She emphasized that it is important to educate providers and parents that children may experience local reactions following booster doses of DTaP, but stressed that these reactions are far lower than those experienced after receipt of the whole-cell vaccines.
The revised pertussis vaccination recommendations are still in draft form and have not yet been finalized.
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