title: Observational study on immune response to yellow fever and measles vaccines in 9 to 15-month old children. Is it necessary to wait 4 weeks between two live attenuated vaccines?
abstract: BACKGROUND
  The use of 2 live attenuated vaccines (LAV) is recommended to be simultaneous or after an interval of at least four weeks between injections. The primary objective of this study was to compare the humoral response to yellow fever (YF) and measles vaccines among children vaccinated against these two diseases, either simultaneously or separated by an interval of 7-28 days.
  
  
  METHODS
  A prospective, multicenter observational study was conducted among children aged 9-15 months. The primary endpoint was the occurrence of positive yellow fever antibodies after YF vaccine by estimating the titers of neutralizing antibodies from venous blood samples. Children vaccinated against YF 7-28 days after receiving the vaccine against measles (test group) were compared with children vaccinated the same day against these two diseases (referent group).
  
  
  RESULTS
  Analysis was performed on 284 children. Of them, fifty-four belonged to the test group. Measles serology was positive in 91.7% of children. Neutralizing antibodies against YF were detected in 90.7% of the test group and 92.9 of the referent group (p=0.6). In addition, quantitative analysis of the immune response did not show a lower response to YF vaccination when it took place 1-28 days after measles vaccination.
  
  
  CONCLUSIONS
  In 1965, Petralli showed a lower response to the smallpox vaccine when injected 4-20 days after measles vaccination. Since then, recommendations are to observe an interval of four weeks between LAV not injected on the same day. Other published studies failed to show a significant difference in the immune response to a LAV injected 1-28 days after another LAV. These results suggest that the usual recommendations for immunization with two LAV may not be correct.
  
  
  CONCLUSIONS
  In low income countries, the current policy should be re-evaluated. This re-evaluation should also be applied to travelers to yellow fever endemic countries.
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal; Centre d'Epidémiologie et de Santé Publique des Armées, Marseille, France; Ecole du Val-de-Grâce, Paris, France. Electronic address: r.michel4@wanadoo.fr.
authors.forename: R
authors.initials: R
authors.lastname: Michel
authors.affiliation: Centre d'Epidémiologie et de Santé Publique des Armées, Marseille, France; Institut Pasteur in French Guiana, Cayenne, France.
authors.forename: F
authors.initials: F
authors.lastname: Berger
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal; Institut Pasteur de Madagascar, Madagascar.
authors.forename: J
authors.initials: J
authors.lastname: Ravelonarivo
authors.affiliation: Institut Pasteur in French Guiana, Cayenne, France.
authors.forename: P
authors.initials: P
authors.lastname: Dussart
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal.
authors.forename: M
authors.initials: M
authors.lastname: Dia
authors.affiliation: Centre d'Investigation Clinique, Epidémiologie Clinique Antilles Guyane (CIC EC CIE802), Centre Hospitalier de Cayenne, Cayenne, French Guiana.
authors.forename: M
authors.initials: M
authors.lastname: Nacher
authors.affiliation: Institut Pasteur de Madagascar, Madagascar.
authors.forename: S
authors.initials: S
authors.lastname: Rogier
authors.affiliation: Institut Pasteur in French Guiana, Cayenne, France.
authors.forename: D
authors.initials: D
authors.lastname: Moua
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal.
authors.forename: F D
authors.initials: FD
authors.lastname: Sarr
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal.
authors.forename: O M
authors.initials: OM
authors.lastname: Diop
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal.
authors.forename: A A
authors.initials: AA
authors.lastname: Sall
authors.affiliation: Institut Pasteur in Dakar, Dakar, Senegal; Global Epidemiology, GSK Vaccines, Wavre, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Baril
mesh_terms: D057134:Antibodies, Neutralizing / Q000097:blood*; D005260:Female; D005616:French Guiana; D006801:Humans; D007110:Immunity, Active; D007115:Immunization Schedule; D007223:Infant; D008297:Male; D008457:Measles / Q000517:prevention & control; D008458:Measles Vaccine / Q000276:immunology*; D011446:Prospective Studies; D012675:Senegal; D013997:Time Factors; D014611:Vaccination; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D015004:Yellow Fever / Q000276:immunology / Q000517:prevention & control; D022341:Yellow Fever Vaccine / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D008458:Measles Vaccine; D014613:Vaccines, Attenuated; D022341:Yellow Fever Vaccine
keywords: Active immune response; Live attenuated vaccine; Measles; Yellow fever