Abstract
BackgroundWe describe the epidemiology of pertussis in Alberta, Canada by person, place, and time between 2004 and 2015, identify outbreak years, and examine vaccination coverage and vaccination timeliness.MethodsWe used health data from Alberta’s Communicable Disease Registry System for the period of January 1, 2004 through August 31, 2015 to identify unique cases of pertussis. Unique cases were deterministically linked to data in Alberta’s immunization repository and health care insurance plan registry. Population estimates and vaccination coverage were extracted from Alberta’s online Interactive Health Data Application. We estimated pertussis incidence rates per 100,000 persons by year, age group, gender, and health zone. Outbreak years were identified using a one-sided cumulative sum (CUSUM) analysis by comparing annual incidence rates to baseline rates.ResultsOver the period, 3510 cases of pertussis were confirmed by laboratory testing or epidemiological linkage. Incidence rates per 100,000 persons were highest in 2004 (20.5), 2005 (13.6), and 2015 (10.4) for all age groups. Incidence rates were highest among the youngest age groups and decreased as age groups increased. Based on CUSUM analysis, 2008 and 2012 met the criteria for outbreak years. Vaccination coverage was over 90% among the general population, however only 61% of cases received at least one dose. About 60% of cases were diagnosed 5+ years after receiving the vaccine. Approximately 87–91% of vaccinated cases did not receive the first three vaccine doses in a timely manner.ConclusionPertussis incidence rates fluctuated over the period across all age groups. The majority of cases had no record of vaccination or were delayed in receiving vaccines. CUSUM analysis was an effective method for identifying outbreaks.
Highlights
We describe the epidemiology of pertussis in Alberta, Canada by person, place, and time between 2004 and 2015, identify outbreak years, and examine vaccination coverage and vaccination timeliness
Acellular pertussis vaccines are routinely administered as pentavalent vaccine [ immunize against diphtheria, tetanus, poliomyelitis, and Haemophilus Influenzae type b (Hib)] for infants and children
There has been a resurgence of pertussis cases in Alberta in the last 15 years among all age groups, despite high vaccination coverage [4]
Summary
We describe the epidemiology of pertussis in Alberta, Canada by person, place, and time between 2004 and 2015, identify outbreak years, and examine vaccination coverage and vaccination timeliness. Acellular pertussis vaccines are routinely administered as pentavalent vaccine [ immunize against diphtheria, tetanus, poliomyelitis, and Haemophilus Influenzae type b (Hib)] for infants and children. A quadrivalent acellular pertussis vaccine ( immunizes against diphtheria, tetanus, and poliomyelitis) is. There has been a resurgence of pertussis cases in Alberta in the last 15 years among all age groups, despite high vaccination coverage [4]. Theories to explain this resurgence include: waning immunity, low vaccine effectiveness, inadequate immune response, lack of boosting, or changes in the disease agent [5,6,7]. Pertussis outbreaks occur cyclically and are expected every 2–5 years [8]
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