文本框: Pertussis efficacy in an acellular Diphtheria–Tetanus–Pertussis containing vaccine – a proven fact
Salmaso S
Istituto Superiore di Sanità, Rome, Italy

In 1992–1993, a randomized double-blind, placebo-controlled clinical trial of two three-component acellular pertussis vaccines was started in Italy. Infants were randomized to receive three doses of one of two acellular pertussis vaccines combined with diphtheria (D) and tetanus (T) toxoids or of a DT vaccine only, at 2, 4, and 6 months of age. Both DTaP vaccines, one manufactured by SmithKline Beecham (DTaP SB; InfanrixTM) and one by Chiron Biocine (DTaP CB; TriacelluvaxTM) contain pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN). After the first period of follow-up, both vaccines had shown a protective efficacy of 84% in the first 2 years of life; when the trial’s follow-up was extended under partial blinding until the participating children had reached 33 months of age, these high levels of efficacy were maintained.

Trial children recipients of DTaPs were further followed in order to estimate the persistence of protection from 3 to 6 years of age. The efficacy in preventing laboratory-confirmed B. pertussis infection and ³14 days of spasmodic cough or ³21 days of any cough was 78% for the DTaP SB vaccine (95% confidence interval [CI]: 71%–83%) and 81% for the DTaP CB vaccine (95% CI: 74%–85%). When using the case-definition based on a more severe clinical presentation (i.e. ³21 days of spasmodic cough), the vaccine efficacy was 86% (95% CI: 79%–91%) for both three-component acellular vaccines.

In addition, effectiveness of DTaP immunization in general population has been confirmed from the results