Abstract
A prolonged pertussis outbreak began in Ontario in November 2011 in an under-immunized religious community and subsequently spread to the general population and a second religious community in the same region of the province. To compare the epidemiology in the religious communities to that of the general population within the affected jurisdictions. The analysis includes cases reported through the integrated Public Health Information System (iPHIS) between November 1, 2011 and April 15, 2013 that met the outbreak case definition. Health unit staff assessed whether cases were members of religious communities through case investigations and collected information on immunization status, treatment and outcomes. A total of 443 confirmed and probable outbreak cases were reported in 7 health units. The outbreak began in one religious community (138 cases), before spreading to the general population in the region (273 cases). A second under-immunized community within the region experienced 32 cases. Thirteen cases were hospitalized and no deaths were reported. Disease peaked earlier in the religious community; cases were significantly younger, more likely to be at high risk for pertussis and more likely to be unimmunized. Among the fully immunized general population, 51% of cases were between 10-14 years and with a median of 5.6 years since their last immunization. The epidemiology of pertussis in the under-immunized community is distinct from the general population. Transmission of pertussis to the general community is not unexpected during an outbreak; however, the proportion of cases up to date with immunization warrants further investigation.
Highlights
Between 2010 and 2012, a number of jurisdictions throughout North America were experiencing pertussis outbreaks. 1-5 Pertussis is a highly communicable respiratory infection caused by Bordetella pertussis, which is most dangerous in infants under one year of age; those under four months. 6,7 Disease control is challenging due to the long period of communicability, the disease’s atypical presentation among adults and immunized children and the fact that it can be difficult to diagnose. 8,9,10Pertussis vaccines have been available in Ontario since 1943
The epidemiology of pertussis in the under-immunized community is distinct from the general population
Our objective is to report on the outbreak investigation, comparing the epidemiology in the religious communities to that of the general population, including demographics, immunization status, treatment and outcomes
Summary
Between 2010 and 2012, a number of jurisdictions throughout North America were experiencing pertussis outbreaks. 1-5 Pertussis is a highly communicable respiratory infection caused by Bordetella pertussis, which is most dangerous in infants under one year of age; those under four months. 6,7 Disease control is challenging due to the long period of communicability, the disease’s atypical presentation among adults and immunized children and the fact that it can be difficult to diagnose. 8,9,10Pertussis vaccines have been available in Ontario since 1943. In 1984, a combination adsorbed whole cell pertussis vaccine was used in the province’s universal publicly-funded immunization program. In 1997, acellular pertussis vaccine replaced the whole cell vaccine and was delivered as part of a combination product (diphtheria [D], tetanus [T], acellular pertussis [aP], inactivated polio vaccine [IPV] and Haemophilus influenzae type b [Hib]) at 2, 4, 6 months of age, with a pentavalent (DTaP-IPV-Hib) booster dose at 18 months and a quadrivalent. In 2003, an adolescent dose was publicly-funded using dTap at 1416 years of age. The outbreak was initially limited to three health units (HUs) and one religious community (A) but subsequently spread to the general community and a second under-immunized religious community (B) in 7 HUs in the province. A prolonged pertussis outbreak began in Ontario in November 2011 in an under-immunized religious community and subsequently spread to the general population and a second religious community in the same region of the province
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