Outbreak of measles in a non-immunizing population, Alberta 2013

Improved vaccine coverage for First Nations children receiving first dose on-reserve: a retrospective cohort study in western Canada

INTRODUCTION

Fragmentation in immunisation reporting systems pose challenges in measuring vaccine coverage for First Nations children in Canada. Some Nations have entered into data-sharing agreements with the province of Alberta's health ministry, enabling novel opportunities to calculate coverage.

METHODS

Partnering with a First Nations community in Alberta, this retrospective cohort study calculated routine childhood vaccine coverage. Administrative data for vaccines delivered within and outside the community were linked to calculate partial and complete immunisation coverage in 2013-2019 at ages 2 and 7 years for children living in the community. We also compared vaccine coverage each year for (a) children who were and were not continuous community residents and (b) children who received or not their first vaccine at the on-reserve community health centre. We also calculated the mean complete coverage across all study years with 95% CIs.

RESULTS

For most vaccines, coverage was higher (p<0.05) at ages 2 and 7 years for children that received their first vaccine at the First Nations health centre, compared with those who received their first dose elsewhere. For example, for pneumococcal vaccine, the mean level of complete coverage in 2-year-olds was 55.7% (52.5%-58.8%) for those who received their first vaccine in the community, compared with 33.3% (29.4%-37.3%) for those who did not; it was also higher at 7 years (75.6%, 72.7%-78.5%, compared with 55.5%, 49.7%-61.3%).

CONCLUSION

Initiating the vaccine series at the on-reserve community health centre had a positive impact on coverage. The ability to measure accurate coverage through data-sharing agreements and vaccine record linkage will support First Nations communities in identifying individual and community immunity. The findings also support the transfer of health funding and service delivery to First Nations to improve childhood immunisation uptake.

Text Message Reminders to Improve Immunization Appointment Attendance in Alberta, Canada: The Childhood Immunization Reminder Project Pilot Study

BACKGROUND

Vaccine coverage for 18-month-old children in Canada is often below the recommended level, which may be partially because of parental forgetfulness. SMS text message reminders have been shown to potentially improve childhood immunization uptake but have not been widely used in Alberta, Canada. In addition, it has been noted that language barriers may impede immunization service delivery but continue to remain unaddressed in many existing reminder and recall systems.

OBJECTIVE

This study aimed to assess the effectiveness and acceptability of using SMS text messages containing a link to web-based immunization information in different languages to remind parents of their child's 18-month immunization appointment.

METHODS

The Childhood Immunization Reminder Project was a pilot intervention at 2 public health centers, one each in Lethbridge and Edmonton, Alberta, Canada. Two SMS text message reminders were sent to parents: a booking reminder 3 months before their child turned 18 months old and an appointment reminder 3 days before their scheduled appointment. Booking reminders included a link to the study website hosting immunization information in 9 languages. To evaluate intervention effectiveness, we compared the absolute attendance no-show rates before the intervention and after the intervention. The acceptability of the intervention was evaluated through web-based surveys completed by parents and public health center staff. Google Analytics was used to determine how often web-based immunization information was accessed, from where, and in which languages.

RESULTS

Following the intervention, the health center in Edmonton had a reduction of 6.4% (95% CI 3%-9.8%) in appointment no-shows, with no change at the Lethbridge Health Center (0.8%, 95% CI -1.4% to 3%). The acceptability surveys were completed by 222 parents (response rate: 23.9%) and 22 staff members. Almost all (>95%) respondents indicated that the reminders were helpful and provided useful suggestions for improvement. All surveyed parents (222/222, 100%) found it helpful to read web-based immunization information in their language of choice. Google Analytics data showed that immunization information was most often read in English (118/207, 57%), Punjabi (52/207, 25.1%), Arabic (13/207, 6.3%), Spanish (12/207, 5.8%), Italian (4/207, 1.9%), Chinese (4/207, 1.9%), French (2/207, 0.9%), Tagalog (1/207, 0.5%), and Vietnamese (1/207, 0.5%).

CONCLUSIONS

The study's findings support the use of SMS text message reminders as a convenient and acceptable method to minimize parental forgetfulness and potentially reduce appointment no-shows. The diverse languages accessed in web-based immunization information suggest the need to provide appropriate translated immunization information. Further research is needed to evaluate the impact of SMS text message reminders on childhood immunization coverage in different settings.

Immunization status of children at kindergarten entry in Alberta, Canada

OBJECTIVES

Little is known about immunization coverage among kindergarten-aged children in jurisdictions that do not require children's immunization records to be provided at school entry. Thus, we assessed immunization coverage and associated characteristics of a 2008 birth cohort of Alberta children at kindergarten entry as compared with at the end of grade one.

METHODS

This retrospective cohort study used population-based administrative health data for childhood vaccines in Alberta, Canada. We categorized and compared immunization status of children as follows: (a) complete at kindergarten entry; (b) incomplete at kindergarten entry but complete at the end of grade one; and (c) still incomplete at the end of grade one. To assess factors associated with immunization status, we used multinomial logistic regression.

RESULTS

Immunization coverage for the complete vaccine series for children (N = 41,515) at kindergarten entry was suboptimal (44.5%, 95% CI 44.0-45.0) and substantially lower than for children at the end of grade one (74.8%, 95% CI 74.3-75.2). Young maternal age, not living with a partner, and having > 1 child in a household were associated with incomplete immunization status at kindergarten entry. Midwife-assisted hospital and home delivery was strongly associated with incomplete immunization status at the end of grade one.

CONCLUSION

Immunization coverage at kindergarten entry was strikingly low. Risk factors for incomplete immunization status were identified that require particular attention when addressing immunization coverage. The school-based catch-up immunization program in grade one seems to have substantially improved coverage among children, suggesting a potential benefit of shifting the catch-up program from grade one to kindergarten entry.

Population immunity to measles in Canada using Canadian Health Measures survey data - A Canadian Immunization Research Network (CIRN) study

We aimed to determine population immunity to measles in Canada, and to assess the risk of future outbreaks. We tested 11,176 sera from Cycles 2 (2009-2011) and 3 (2011-2013) cohorts from the biobank of Statistics Canada's Canadian Health Measures Survey (CHMS) using the BioPlex 2220 MMRV IgG assay. We then tested all BioPlex negative and equivocal samples using a more sensitive Plaque Reduction Neutralization Test (PRNT). We determined the weighted proportion of positive, equivocal, and negative samples by age, sex, region and whether individuals were born in Canada. We found that 90.0% (95% confidence interval (CI): 88.2, 91.9) of samples were positive, 4.5% (95% CI: 3.4, 5.5) were equivocal and 5.5% (95% CI: 4.3, 6.7) were negative. Individuals in the 12-19 year age band had the lowest proportion positive at 78.7% (95% CI: 74.2, 83.2) and the highest proportion of positive samples was found in those 60-79 years (99.6%, 95% CI: 99.3, 99.9). Seropositivity was consistently <90% across a broad range of pediatric and adult age bands (6-39 years). We found that a slightly higher proportion of females were positive (91.9%, 95% CI: 90.1, 93.6) compared to males (88.3%, 95% CI: 85.8, 90.7). When taking into account interaction between age and born in Canada status, we found individuals born in Canada aged 19 and under were less susceptible (OR = 0.6 (95% CI: 0.4, 0.95)) compared to those born outside Canada whereas, those aged 20 and over were more susceptible (OR = 1.7 (95% CI: 1.1, 2.8)). Our findings indicate that measles immunity in Canada is below the 95% immunity threshold required to sustain measles elimination, underscoring the importance of maintaining high vaccine coverage to prevent future measles outbreaks and sustain Canada's elimination status.

Impact of the COVID-19 pandemic on vaccine coverage for early childhood vaccines in Alberta, Canada: a population-based retrospective cohort study

OBJECTIVE

To assess the impact of the COVID-19 pandemic on early childhood vaccination coverage in Alberta, Canada.

SETTING

Alberta, a western Canadian province, which has a population of 4.4 million and approximately 50 000 births annually.

DESIGN

In this retrospective cohort study, population-based administrative health data were analysed to determine the vaccination coverage for measles-containing, pertussis-containing and rotavirus vaccines.

PRIMARY OUTCOME MEASURE

We measured monthly and cumulative vaccine coverage. We assessed the absolute difference in monthly and cumulative coverage for each vaccine dose by comparing children due for vaccination in each month of 2019 and 2020, with follow-up to determine if missed doses were caught up later.

PARTICIPANTS

We included 114 178 children in the 2019 analysis cohort and 106 530 children in the 2020 analysis cohort.

RESULTS

Monthly vaccination coverage in 2020 was higher than 2019 until March, when coverage significantly declined. Comparing April 2020 to 2019, coverage was 9.9% (95% CI 7.9% to 12.0%) lower for measles vaccine; 4.9% (95% CI 3.3% to 6.5%), 7.1% (95% CI 5.2% to 9.1%), 5.2% (95% CI 3.1% to 7.4%) and 8.8% (95% CI 6.6% to 10.9%) lower for first, second, third and fourth doses of pertussis-containing vaccine, respectively; and 4.0% (95% CI 2.3% to 5.7%), 7.1% (95% CI 5.1% to 9.2%) and 4.6% (95% CI 2.4% to 6.7%) lower for first, second and third doses of rotavirus vaccine, respectively. Monthly coverage improved during May to July 2020; however, some doses experienced a second decline during September to October 2020. The cumulative coverage analysis showed that the measles-containing vaccine had the largest difference in coverage at the end of follow-up.

CONCLUSIONS

Children who were due for vaccination early in the pandemic and in Fall 2020, especially those due for measles vaccination, may require additional catch-up.

An equity-based assessment of immunization-related responses in urban Alberta during the 2014 measles outbreak: a comparative analysis between Calgary and Edmonton

OBJECTIVES

This study investigates measles, mumps, and rubella (MMR) immunization rates during the measles outbreak in Calgary and Edmonton of 2014 stratified by four area-level socio-demographic indicators. This study also leverages this epidemiological data to assess the equity aspect of emergency measures instituted regarding immunization in those two cities.

METHODS

A mixed-methods comparative case study analysis methodology was employed to assess the neighbourhood-level immunization statuses before (2013), during (2014), and after (2015) an active measles outbreak in Calgary and Edmonton, Alberta, Canada. The epidemiological one-dose by age-2 MMR coverage data were stratified using four socio-demographic indicators: median household income, %-homeownership, %-Aboriginal population, and %-immigrant population. Document and content analysis was utilized to investigate the outbreak mitigation strategies deployed in each city.

RESULTS

The measles outbreak of 2013/2014 involved the entirety of Alberta and led to both provincial and city-specific interventions in which Calgary deployed three mass immunization clinics in 2014, where Edmonton did not. The Calgary coverage data showed an increase in coverage inequalities across all indicators and the Edmonton data showed mixed results in terms of equity gains/losses. Calgary's additive intervention of three mass immunization clinics in 2014 appears to have contributed to both the higher gross immunization rates in Calgary (90.77%) and an inequitable increase in coverage rates as compared with Edmonton (88.96%), in most cases.

CONCLUSION

Public health policy-makers must be cognizant that large-scale public health efforts must be optimized for accessibility across all socio-economic levels to ensure public and population health gains are realized equitably.

Evaluation of Diagnostic Accuracy of Eight Commercial Assays for the Detection of Measles Virus-Specific IgM Antibodies

The World Health Organization (WHO) has targeted measles for global eradication through mass immunization. For effective monitoring of eradication targets, high-quality surveillance is needed. The detection of IgM antibodies, specific to the measles virus, with the use of commercial enzyme-linked immunosorbent assays (ELISA or EIA) is broadly used within the WHO global measles and rubella laboratory network for laboratory confirmation, and in particular, ELISA kits manufactured by Siemens (Enzygnost kits) have been primarily used. Spurred by the discontinuation of these kits, this study aims to report on the clinical sensitivity and specificity of comparable commercial ELISA kits and one automated chemiluminescent immunoassay (CLIA) method. A panel of 239 serum samples was assembled that included sera from confirmed measles cases (n = 50) and probable post-MMR vaccine response (n = 2). Measles-negative sera (n = 187) were collected from individuals presenting with other fever and rash illnesses. A total of 7 ELISA kits (Euroimmun native antigens and recombinant nucleoprotein, IBL, Clin-Tech Microimmune, NovaTec NovaLisa, Serion, and Siemens Enzygnost) and one CLIA method (DiaSorin LIAISON XL) were evaluated. The ELISA kits included two IgM capture methods and five indirect methods. Calculated sensitivities and specificities ranged from 75.0% to 98.1% and 86.6% to 99.5%, respectively. The parvovirus B19 IgM positive sera were noted to cause false-positive results, particularly for the ELISA kits from Serion and NovaLisa; specificities for this subset of samples ranged from 51.4% to 100.0%. The capture IgM ELISA methods provided the best combination of sensitivity and specificity.

Vaccine hesitancy among parents of preschoolers in Canada: a systematic literature review

OBJECTIVES

The purpose was to synthesize the available literature on what factors influence vaccine hesitancy of parents of preschoolers in Canada.

METHODS

Databases (e.g., CINAHL, PubMed, OVID, Proquest) were searched for relevant research articles produced between January 2009 and October 2019. Articles were required to examine vaccine uptake in children aged 0-7, in the English language, and focused within a Canadian context. Articles were excluded if they focused on uptake of the influenza vaccine and if the study population was children with chronic health conditions. A total of 367 articles were reviewed and 12 met the criteria for inclusion in this review.

SYNTHESIS

This review found that between 50% and 70% of children are completely vaccinated at 2 years old, with up to 97% having received at least one vaccine, and 2-5% receiving no vaccines. This review found that trust and access to health care providers is significantly associated with vaccine uptake, likely more important than parents' vaccine knowledge, and may compensate for challenges related to socio-economic status and family dynamics.

CONCLUSION

Vaccine programs need to be created that are accessible to all families, with an awareness of the significant impact of trust on vaccine uptake. Future research should include consistent measures of vaccine uptake, and data from First Nation communities, and should examine how increased trust between health care providers and parents of preschool children would increase vaccine uptake in Canada.

Cost-effectiveness of measles control during elimination in Ontario, Canada, 2015

BackgroundGiven that measles is eliminated in Canada and measles immunisation coverage in Ontario is high, it has been questioned whether Ontario's measles outbreak response is worthwhile.AimOur objective was to determine cost-effectiveness of measles containment protocols in Ontario from the healthcare payer perspective.MethodsWe developed a decision-analysis model comparing Ontario's measles containment strategy (based on actual 2015 outbreak data) with a hypothetical 'modified response'. The modified scenario assumed 10% response costs with reduced case and contact tracing and no outbreak-associated vaccinations; it was based on local and provincial administrative and laboratory data and parameters from peer-reviewed literature. Short- and long-term health outcomes, quality-adjusted life years (QALYs) and costs discounted at 1.5%, were estimated. We conducted one- and two-way sensitivity analyses.ResultsThe 2015 outbreak in Ontario comprised 16 measles cases and an estimated 3,369 contacts. Predictive modelling suggested that the outbreak response prevented 16 outbreak-associated cases at a cost of CAD 1,213,491 (EUR 861,579). The incremental cost-effectiveness ratio was CAD 739,063 (EUR 524,735) per QALY gained for the outbreak response vs modified response. To meet the commonly accepted cost-effectiveness threshold of CAD 50,000 (EUR 35,500) per QALY gained, the outbreak response would have to prevent 94 measles cases. In sensitivity analyses, the findings were robust.ConclusionsOntario's measles outbreak response exceeds generally accepted cost-effectiveness thresholds and may not be the most efficient use of public health resources from a healthcare payer perspective. These findings should be balanced against benefits of increased vaccine coverage and maintaining elimination status.

A new resource to summarize evidence on immunization from the Canadian Vaccination Evidence Resource and Exchange Centre (CANVax)

Scientific progress around the development, use and best practices for communicating the benefits of vaccines is rapid, and keeping up-to-date with the substantial body of evidence on these topics is challenging. However, the increase in the number of vaccines and decline in vaccine-preventable illnesses has often focused public attention more on the risks of vaccines rather than the risks of the diseases. In Canada and elsewhere, an increasing number of parents are choosing to delay and/or refuse some or all vaccines for their children, leading to declining community protection against vaccine-preventable diseases and an increase in the number of outbreaks of vaccine-preventable diseases. Evidence suggests that the concept of vaccine hesitancy contributes to a deeper understanding of vaccination decisions by moving beyond the traditional binary of pro- or anti-vaccine attitudes to recognize a spectrum of beliefs and associated behaviours that occupies the space between the two poles. At a time of growing antimicrobial resistance to infections, protection conferred by vaccination is more important than ever. The Canadian Vaccination Evidence Resource and Exchange Centre (CANVax) is an online curated database of resources to support immunization and promotional activities aimed at improving vaccine acceptance and uptake in Canada. It includes both the identification of accurate and reliable resources and the creation of new resources by a group of multidisciplinary professionals. This issue of the Canada Communicable Disease Report (CCDR) includes the first of a series of "CANVax Briefs" that have been developed by experts after conducting scoping reviews and environmental scans and assessing the most rigorous evidence. The aim of the CANVax Briefs is to bring attention to current and emerging issues by providing short summaries of the recent best available evidence to assist frontline public health and clinical care professionals in optimizing the immunization rate in Canada. CANVax Briefs will be published in CCDR throughout 2020.

Public health responses during measles outbreaks in elimination settings: Strategies and challenges

In late September 2016, the Americas became the first region in the world to have eliminated endemic transmission of measles virus. Several other countries have also verified measles elimination, and countries in all six World Health Organization regions have adopted measles elimination goals. The public health strategies used to respond to measles outbreaks in elimination settings are thus becoming relevant to more countries. This review highlights the strategies used to limit measles spread in elimination settings: (1) assembly of an outbreak control committee; (2) isolation of measles cases while infectious; (3) exclusion and quarantining of individuals without evidence of immunity; (4) vaccination of susceptible individuals; (5) use of immunoglobulin to prevent measles in exposed susceptible high-risk persons; (6) and maintaining laboratory proficiency for confirmation of measles. Deciding on the extent of containment efforts should be based on the expected benefit of reactive interventions, balanced against the logistical challenges in implementing them.

Timeliness and completeness of routine childhood vaccinations in children by two years of age in Alberta, Canada

OBJECTIVES

Assessing timeliness and completeness of vaccine administration is important for evaluating the effectiveness of immunization programs. Few studies have reported timeliness, particularly in Canada. The objective of this study was to examine timeliness of the receipt of vaccination for each routine childhood recommended vaccine by 24 months of age among children in a community-based pregnancy cohort in Calgary, Alberta.

METHODS

Survey data from a community-based pregnancy cohort in Alberta were linked to Public Health vaccination records of children (n = 2763). The proportion of children receiving early, timely, delayed, or no vaccination was calculated. A dose was considered early if it was administered before the recommended age in days as per the vaccination schedule, timely if administered at any time from start of recommended age in days to age in days when delay counts were initiated, and delayed if it was administered on or after age in days when delay counts were initiated. Series completion rates were also calculated.

RESULTS

For multi-dose vaccines, over 80% of children had timely doses at 2, 4 and 6 months. By 12 months, this proportion decreased to 65% (95% CI: 63%-66%) for meningococcal conjugate group C, 61% (95% CI: 59%-62%) for measles antigen-containing vaccines and 64% (95% CI: 62%-65%) for varicella antigen-containing vaccines. At 18 months, only 55% (95% CI: 53%-56%) of the children had a timely 4th dose of diphtheria, acellular pertussis, tetanus, polio, and Haemophilus influenzae type b vaccine. Eventual series completion rate for all recommended vaccines was 77% (95% CI: 75%-79%).

CONCLUSION

The timeliness and completeness of routine childhood vaccination in preschool children in this community-based pregnancy cohort is lower than provincial targets. Data on timeliness of vaccination can inform further work on barriers and enablers to vaccination in order to meet provincial targets.

Large measles epidemic in the Netherlands, May 2013 to March 2014: changing epidemiology

Since the early 1990s, the Netherlands has experienced several large measles epidemics, in 1992–94, 1999–2000 and in 2013–14. These outbreaks mainly affected orthodox Protestants, a geographically clustered population with overall lower measles-mumps-rubella first dose (MMR-1) vaccination coverage (60%) than the rest of the country (> 95%). In the 2013–14 epidemic described here, which occurred between 27 May 2013 and 12 March 2014, 2,700 cases were reported. Several control measures were implemented including MMR vaccination for 6–14-month-olds and recommendations to reduce the risk in healthcare workers. The vast majority of reported cases were unvaccinated (94%, n = 2,539), mostly for religious reasons (84%, n = 2,135). The median age in the epidemic was 10 years, 4 years older than in the previous epidemic in 1999–2000. A likely explanation is that the inter-epidemic interval before the 2013–2014 epidemic was longer than the interval before the 1999–2000 epidemic. The size of the unvaccinated orthodox Protestant community is insufficient to allow endemic transmission of measles in the Netherlands. However, large epidemics are expected in the future, which is likely to interfere with measles elimination in the Netherlands and elsewhere.

A Measles Outbreak in an Underimmunized Amish Community in Ohio

BACKGROUND

Although measles was eliminated in the United States in 2000, importations of the virus continue to cause outbreaks. We describe the epidemiologic features of an outbreak of measles that originated from two unvaccinated Amish men in whom measles was incubating at the time of their return to the United States from the Philippines and explore the effect of public health responses on limiting the spread of measles.

METHODS

We performed descriptive analyses of data on demographic characteristics, clinical and laboratory evaluations, and vaccination coverage.

RESULTS

From March 24, 2014, through July 23, 2014, a total of 383 outbreak-related cases of measles were reported in nine counties in Ohio. The median age of case patients was 15 years (range, <1 to 53); a total of 178 of the case patients (46%) were female, and 340 (89%) were unvaccinated. Transmission took place primarily within households (68% of cases). The virus strain was genotype D9, which was circulating in the Philippines at the time of the reporting period. Measles-mumps-rubella (MMR) vaccination coverage with at least a single dose was estimated to be 14% in affected Amish households and more than 88% in the general (non-Amish) Ohio community. Containment efforts included isolation of case patients, quarantine of susceptible persons, and administration of the MMR vaccine to more than 10,000 persons. The spread of measles was limited almost exclusively to the Amish community (accounting for 99% of case patients) and affected only approximately 1% of the estimated 32,630 Amish persons in the settlement.

CONCLUSIONS

The key epidemiologic features of a measles outbreak in the Amish community in Ohio were transmission primarily within households, the small proportion of Amish people affected, and the large number of people in the Amish community who sought vaccination. As a result of targeted containment efforts, and high baseline coverage in the general community, there was limited spread beyond the Amish community. (Funded by the Ohio Department of Health and the Centers for Disease Control and Prevention.).

Applications of geographic information systems in public health: A geospatial approach to analyzing MMR immunization uptake in Alberta

OBJECTIVE

This study evaluates the temporal, spatial, and spatio-temporal variation of immunization rates for measles, mumps and rubella (MMR) immunization in the province of Alberta. The study uses yearly immunization rate data for Health Zones and Local Geographic Areas (2004-2012), which were obtained from Alberta Health's Interactive Health Data Application (IHDA).

METHODS

Spatial analyses include a global spatial analysis, Moran's I, and local indicators of spatial association (LISA) analysis - Getis and Ord's G* - to identify clusters of high or low immunization rates. Spatial methods are then applied to a time series analysis to examine how the immunization rates change over time in conjunction with space.

RESULTS

Mapped results indicate decreasing immunization rates over time for the majority of the province where most local geographic areas (LGAs) fall short of the 95% herd immunity threshold. Clusters of high immunization rates in the metropolitan centres, and clusters of low immunization rates in the southern and northern region of the province exist spatially and spatio-temporally. Over time, the high rate clusters are decreasing in size and the low rate clusters are increasing.

CONCLUSION

This research provides a localized geographic approach to assessing MMR immunization rates in Alberta. Findings from this research can be used to target public health interventions to specific areas that exhibit the lowest immunization rates. These results can also be used for hypothesis generation in future research on barriers to immunization uptake.

Measles in Canada Between 2002 and 2013

Background.  In 1994, Canada committed to eliminate measles by the year 2000. This report presents the epidemiology of measles in Canada between 2002 and 2013 and its implications in sustaining measles elimination. Methods.  Cases included individuals reported to the Canadian Measles and Rubella Surveillance System with confirmed measles. Results.  In Canada, 1171 cases of measles were reported between 2002 and 2013 (incidence 0.29 cases per 100 000 population). The annual number of cases ranged from 6 to 752. The majority of cases were unvaccinated (63%) or had an unknown vaccination status (19%). The median age of cases was 14.4 years (range, <1 to 63 years) globally and 14 years when excluding the 2011 outbreak in Quebec where 68% of the 678 cases were 10 to 19 years old. With the exclusion of this outbreak, the incidence was highest in infants (1.0 per 100 000), lower but fairly similar between 1 and 19 years of age (0.2 to 0.4 per 100 000), and there was a substantial decline between 20 and 39 years of age (0.1 per 100 000). There was a significant trend towards a greater annual number of importations over the period. Although importations resulted in no transmission sustained for ≥12 months, 5 chains of transmission had >30 cases. The effective reproductive number between 2002 and 2013 was estimated at 0.86 (95% confidence interval, .81-.92). Conclusions.  Canada has maintained elimination between 2002 and 2013, but additional efforts are needed to reduce the proportion of unimmunized individuals and respond to importation events.

Measles surveillance in Canada: Trends for 2013

OBJECTIVE

The objective of this report is to describe measles activity in Canada during 2013, in order to support the documentation and maintenance of measles elimination status.

METHODS

A descriptive analysis of measles counts and incidence by age group, immunization history, hospitalization and province/territory, as well as a summary of 2013 outbreaks, was conducted using enhanced measles data captured through the Canadian Measles and Rubella Surveillance System. Genotype information and phylogenetic analysis for 2013 were summarized.

RESULTS

In 2013, 83 confirmed measles cases were reported in seven provinces/territories for an incidence rate of 2.4 per 1,000,000 population. Incidence was highest in the youngest age groups (< 1 year, 1 to 4 years). Burden of disease was highest in the youngest age groups and children 10 to 14 years. Three-quarters of cases had been inadequately immunized, and 10% were hospitalized. There were nine measles outbreaks reported in 2013, one of which consisted of 42 cases in a non-immunizing community in Alberta.

DISCUSSION

2013 saw the fifth highest number of reported measles cases since 1998. While we continue to face challenges related to importation and heterogeneous immunization coverage, in 2013 Canada met or partially met all four criteria outlined by the Pan American Health Organization for measles elimination.

The challenges of sustaining measles elimination in Canada

Recent importations of measles into Canada have not generally led to large outbreaks, indicating that measles is well controlled in Canada. Isolated large outbreaks that have occurred remind us of the need to remain vigilant. Measles presents particular challenges because it is the most infectious disease known, it thrives among those who do not access the child health system for one reason or another, and we do not always have the information we need to identify and target communities with low immunization coverage. Outbreaks typically arise from Canadians who travel and are exposed to measles abroad. Controlling sporadic outbreaks arising from importations is time and resource intensive, which makes immunization for Canadians travelling outside the region of the Americas (where measles has been eliminated) a priority. To prevent importations of measles into Canada altogether requires other countries and regions of the world to make progress in eliminating measles.