Background and aims: Pertussis is a contagious bacterial disease. During 2011-2012 pertussis incidence rates in Israel soared, especially in infants under 1 year (>300/100,000). We aimed to investigate risk markers for pertussis.
Methods: A case-control study in the Jerusalem district (1998–2011). Data collected: epidemiological and clinical investigations and vaccination records. Vaccination status was defined as number of pertussis vaccine doses received (the current routine schedule includes 3 doses at 2,4,6 months, booster doses at 12 months, 7y and 13y)
Results: The study population included 1268 infants under 1 year: 317 pertussis cases and 951 age-matched controls (mean age 3.95±3.01, median 2.9 months). The cases had a higher proportion of males (56.8% vs. 50.8%), of low birthweight (<2500 gram, 12.3% vs. 6.3%) and a higher child's rank in the family (53% ranked 4 and above vs. 37.7%). Some 40% of the cases (127/317) were hospitalized, most (111,87.4%) were under 4 months (mean age 2.42±2.1, median 1.83 months).
Vaccination status: the distribution of 0,1,2 and 3 pertussis vaccine doses differed significantly being 62%,21.7%,10.7%,5.7% vs. 43.3%,26.6%,15%,15% among cases and age-matched controls, respectively. The proportion of unvaccinated infants (age-appropriate) at ages 2-3,4-5 and 6+ months was 56.8%,29.8% and 34.8% vs. 30.4%,9% and 4.6% among cases and controls. The vaccine effectiveness was 84%,71% and 67% for 3, 2 and 1 pertussis vaccine doses, respectively.
Conclusions: Specific risk markers to pertussis were identified. Pertussis cases were significantly more likely to be unvaccinated and to have delayed vaccinations. Vaccine effectiveness increased with the number of vaccine doses.
Conclusions: Specific risk markers to pertussis were identified. Pertussis cases were significantly more likely to be unvaccinated and to have delayed vaccinations. Vaccine effectiveness increased with the number of vaccine doses.
