Persistence of protection through 33 months of age provided by immunization in infancy with two three-component acellular pertussis vaccines

Stefania Salmaso, Paola Mastrantonio, Steven G F Wassilak, Marina Giuliano, Alessandra Anemona, Anna Giammanco, Alberto E. Tozzi, Marta L. Ciofi Degli Atti, Donato Greco, P. Panei, G. Scuderi, S. Luzi, G. Canganella, F. R. Meduri, P. Stefanelli, M. Bottone, T. Sofia, A. Chiarini, M. Maggio, S. TaorminaM. Genovese, A. Moiraghi, A. Barale, S. Di Tommaso, S. Malaspina, E. Vasile, P. Ferraro, P. L. Dal Lago, L. De Marzi, L. Robino, E. Giraldo, N. Coppola, P. Materassi, G. Tarabini Castellani, F. Basso, S. Barbuti, M. Quarto, P. Lopalco, P. D'Orazio, C. Germinario

Research output: Contribution to journalArticlepeer-review


A large, randomized, placebo-controlled clinical trial in Italy on two three-component pertussis vaccines, given as DTaP in infancy, one manufactured by SmithKline and Beecham (SB) and one by Chiron Biocine (CB), found each vaccine to be 84% efficacious through the average age of 24 months. The cohort of children enrolled in the trial was followed with unmodified case ascertainment procedures for nine additional calendar months, during which partial unblinding occurred, for the unvaccihated randomized group. For the DTaP groups, the specific vaccine assignment remained double- blinded throughout the entire additional observation period. Pertussis was defined as paroxysmal cough lasting at least 21 days and confirmed by culture or serology. In the additional 9 months the observed absolute efficacy was 78% (95% CI, 62-87%) for SB DTaP vaccine and 89% (95% CI, 79-94%) for CB DTaP. The relative risk of developing pertussis in SB DTaP recipients compared to CB DTaP vaccinees was 1.99 (95% CI, 1.13-3.51). By combining observations from the initial and additional follow-up periods, the overall observed vaccine efficacy through an average age of 33 months of SB DTaP was 80% and of CB DTaP, 85%.

Original languageEnglish
Pages (from-to)1270-1275
Number of pages6
Issue number13
Publication statusPublished - Aug 1998


  • Acellular vaccine
  • Efficacy
  • Pertussis

ASJC Scopus subject areas

  • Immunology
  • Microbiology
  • Virology
  • Infectious Diseases
  • Public Health, Environmental and Occupational Health
  • veterinary(all)


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