Clinical Trial: Pertussis Immunization Programs in Low Income Countries

Study Status: Recruiting
Recruit Status: Recruiting
Study Type: Observational

Official Title: Pertussis Immunization Programs in Low Income Countries

Brief Summary:

Due to waning of infectious as well as vaccine immunity and lack of vaccination boosters, a large number of adolescents and adults are no longer immunized against Bordetella pertussis, the agent of whooping cough and consequently may contract whooping cough. Furthermore, these populations represent a reservoir of the infectious agent from which the dissemination to non-immune infants is possible, causing severe illness, or even death, in this age group.

Few studies have been carried out on whooping cough in developing countries (incidence, contaminator's age, etc.) and, specifically, none have assessed the duration of protection induced by the whole cell pertussis (wP) vaccine mainly presently used in these countries.

However, data on the duration of vaccine induced protection are essential to determine i) the usefulness of vaccine boosters and ii) the target age group for these boosters.

The aims of the present study are:

• To evaluate the proportion of confirmed pertussis cases in infants presenting whooping cough syndrome (WP1a)
• To evaluate the proportion of confirmed pertussis cases or healthy carriers among contact cases
• To determine origin of the infant's contamination (WP1b)
• To determine the duration of protection induced by the wP vaccines used in contact cases and the child population aged 3 to 15 yo (WP1b and WP2)
• To bring new scientific evidences documenting the potential need for initiating boosters (WP1b and WP2)
• To allow a comparison of the results with those obtained using the same methodology for the acellul
  

  Detailed Summary:

  Background:

  Vaccination of infants and young children with a whole-cell pertussis (wP) vaccine dramatically decreased the mortality and morbidity due to B. pertussis. However, twenty-five years of "honeymoon" period, after the introduction of high vaccination coverage, reappearance of whooping cough cases in industrialized countries was observed in infants contaminated by adolescents and adults. This modification in transmission of the disease after the introduction of the wP vaccine indicated that the immunity provided by the vaccine is not lifelong, just like that provided by natural infection, and that it decreases7-9 years after the first vaccination and the first booster. Due to secondary effects, wP vaccines cannot be used for boosters. Moreover, the wP vaccines have been shown to be different in terms of efficacy (varying from 30 to 95%). Acellular pertussis (aP) vaccines consisting of purified and inactivated bacterial proteins, have therefore been developed and commercialized. These vaccines induce much fewer side effects and may therefore be used for primary-vaccination as well as for vaccine boosters. They are expensive but have more reproducible manufacturing. The humoral and long-term cell-mediated immunities granted by the aP vaccines have been shown to be comparable to the immunity granted by the wP vaccines, effective for 6-7 years after the booster vaccine in the second year of life, also inducing different cell immunity. Since 2007, the proportion of B. pertussis and B. parapertussis isolates no longer producing vaccine antigen(s) has increased in the industrialized countries that use aP vaccines. These isolates may decrease the efficacy of the aP vaccines. Does this type of isolates circulate in the Low income countries still using wP vaccines ? Does it reduce the efficacy of the wP vaccines? Moreover, the wP vaccines used in the Southern coun
  Sponsor: Institut Pasteur
  

  Current Primary Outcome:

  • Proportion of biologically confirmed cases of pertussis in patients under 6 months old admitted into hospital with clinical signs corresponding to whooping cough syndrome. [ Time Frame: November 2018 ]
    Primary Outcome of WP1a (Cohort 1)
  • Proportion of cases tested positive for B.Pertussis given by the presence of B. pertussis DNA in the nasopharyngeal sample or by the presence of an anti-pertussis toxin IgG level >100 IU/mL in the serum. [ Time Frame: November 2018 ]
    Primary Outcome of WP1b (Cohort 2)
  • Proportion of cases tested positive given by the presence of an anti-pertussis toxin IgG level >100 IU/mL in the serum. [ Time Frame: November 2018 ]
    Primary Outcome of WP2 (Cohort 3)
  
  
  

  Original Primary Outcome: Same as current
  
  

  Current Secondary Outcome: Estimation of the relative risk of the disease occurring in the contact patients based on their immunization status and age groups [ Time Frame: April 2019 ]
  
  

  Original Secondary Outcome: Same as current
  
  Information By: Institut Pasteur
  

  Dates:
  Date Received: November 17, 2016
  Date Started: January 22, 2017
  Date Completion: November 2019
  Last Updated: March 21, 2017
  Last Verified: March 2017