Measuring waning protection from seasonal influenza vaccination during nine influenza seasons, Ontario, Canada, 2010/11 to 2018/19.

BackgroundWaning immunity from seasonal influenza vaccination can cause suboptimal protection during peak influenza activity. However, vaccine effectiveness studies assessing waning immunity using vaccinated and unvaccinated individuals are subject to biases.AimWe examined the association between time since vaccination and laboratory-confirmed influenza to assess the change in influenza vaccine protection over time.MethodsUsing linked laboratory and health administrative databases in Ontario, Canada, we identified community-dwelling individuals aged ≥ 6 months who received an influenza vaccine before being tested for influenza by RT-PCR during the 2010/11 to 2018/19 influenza seasons. We estimated the adjusted odds ratio (aOR) for laboratory-confirmed influenza by time since vaccination (categorised into intervals) and for every 28 days.ResultsThere were 53,065 individuals who were vaccinated before testing for influenza, with 10,264 (19%) influenza-positive cases. The odds of influenza increased from 1.05 (95% CI: 0.91-1.22) at 42-69 days after vaccination and peaked at 1.27 (95% CI: 1.04-1.55) at 126-153 days when compared with the reference interval (14-41 days). This corresponded to 1.09-times increased odds of influenza every 28 days (aOR = 1.09; 95% CI: 1.04-1.15). Individuals aged 18-64 years showed the greatest decline in protection against influenza A(H1N1) (aORper 28 days = 1.26; 95% CI: 0.97-1.64), whereas for individuals aged ≥ 65 years, it was against influenza A(H3N2) (aORper 28 days = 1.20; 95% CI: 1.08-1.33). We did not observe evidence of waning vaccine protection for individuals aged < 18 years.ConclusionsInfluenza vaccine protection wanes during an influenza season. Understanding the optimal timing of vaccination could ensure robust protection during seasonal influenza activity.

A Call for Caution in Use of Pertussis Vaccine Effectiveness Studies to Estimate Waning Immunity: A Canadian Immunization Research Network Study.

BACKGROUND: Vaccine effectiveness (VE) studies provide essential evidence on waning vaccine-derived immunity, a major threat to pertussis control. We evaluated how study design affects estimates by comparing 2 case-control studies conducted in Ontario, Canada. METHODS: We compared results from a test-negative design (TND) with a frequency-matched design (FMD) case-control study using pertussis cases from 2005-2015. In the first study, we identified test-negative controls from the public health laboratory that diagnosed cases and, in the second, randomly selected controls from patients attending the same physicians that reported cases, frequency matched on age and year. We compared characteristics of cases and controls using standardized differences. RESULTS: In both designs, VE estimates for the early years postimmunization were consistent with clinical trials (TND, 84%; FMD, 89% at 1-3 years postvaccination) but diverged as time since last vaccination increased (TND, 41%; FMD, 74% by 8 years postvaccination). Overall, we observed lower VE and faster waning in the TND than the FMD. In the TND but not FMD, controls differed from cases in important confounders, being younger, having more comorbidities, and higher healthcare use. Differences between the controls of each design were greater than differences between cases. TND controls were more likely to be unvaccinated or incompletely vaccinated than FMD controls (P < .001). CONCLUSIONS: The FMD adjusted better for healthcare-seeking behavior than the TND. Duration of protection from pertussis vaccines is unclear because estimates vary by study design. Caution should be exercised by experts, researchers, and decision makers when evaluating evidence on optimal timing of boosters.

The impact of varicella vaccination on paediatric herpes zoster epidemiology: a Canadian population-based retrospective cohort study.

The impact of universal varicella vaccination on herpes zoster (HZ) risk in unvaccinated and vaccinated children, and its long-term influence on HZ epidemiology, remains unknown. We conducted a retrospective cohort study using population-based administrative health data for children born between 1993 and 2018 (n = 924,124). We calculated age-specific cumulative HZ incidence rates by vaccination status for cohorts born before (1993-1999) and after (2000-2018) programme implementation; results were used to calculate relative risk of HZ by age group, vaccination status and vaccine availability period. Annual HZ incidence rates were calculated for 1993-2018. HZ risk was higher among unvaccinated children compared to vaccinated children across age groups; 64% higher before universal vaccination (RR: 0.36, 95% CI: 0.33, 0.39), and 32% higher after universal vaccination (RR: 0.68, 95% CI: 0.64, 0.73). Among unvaccinated children, HZ risk was 60% lower after vaccine programme implementation (RR: 0.40, 95% CI: 0.38, 0.43). Two-dose receipt corresponded with a 41% lower risk of HZ compared to one-dose receipt (RR: 0.59, 95% CI: 0.53, 0.65). Crude annual HZ incidence rates declined 64% after programme implementation, with decreases observed across age groups. Universal varicella vaccination programme implementation corresponds to decreased paediatric HZ incidence across age groups, in both vaccinated and unvaccinated individuals. Results from this study can be used to help inform varicella vaccination programme decision-making in other countries.

Epidemiology and Clinical Outcomes of Hospitalizations for Acute Respiratory or Febrile Illness and Laboratory-Confirmed Influenza Among Pregnant Women During Six Influenza Seasons, 2010-2016.

BACKGROUND: Pregnant women are at increased risk of seasonal influenza hospitalizations, but data about the epidemiology of severe influenza among pregnant women remain largely limited to pandemics. METHODS: To describe the epidemiology of hospitalizations for acute respiratory infection or febrile illness (ARFI) and influenza-associated ARFI among pregnant women, administrative and electronic health record data were analyzed from retrospective cohorts of pregnant women hospitalized with ARFI who had testing for influenza viruses by reverse-transcription polymerase chain reaction (RT-PCR) in Australia, Canada, Israel, and the United States during 2010-2016. RESULTS: Of 18 048 ARFI-coded hospitalizations, 1064 (6%) included RT-PCR testing for influenza viruses, 614 (58%) of which were influenza positive. Of 614 influenza-positive ARFI hospitalizations, 35% were in women with low socioeconomic status, 20% with underlying conditions, and 67% in their third trimesters. The median length of influenza-positive hospitalizations was 2 days (interquartile range, 1-4), 18% (95% confidence interval [CI], 15%-21%) resulted in delivery, 10% (95% CI, 8%-12%) included a pneumonia diagnosis, 5% (95% CI, 3%-6%) required intensive care, 2% (95% CI, 1%-3%) included a sepsis diagnosis, and <1% (95% CI, 0%-1%) resulted in respiratory failure. CONCLUSIONS: Our findings characterize seasonal influenza hospitalizations among pregnant women and can inform assessments of the public health and economic impact of seasonal influenza on pregnant women.

The association between influenza vaccination and socioeconomic status in high income countries varies by the measure used: a systematic review.

BACKGROUND: The purpose of this paper is to systematically review the literature on the relationship between socioeconomic status (SES) and influenza immunization and to examine how certain measures of SES may influence interpretations of this relationship. METHODS: We conducted a systematic review of existing peer-reviewed literature to evaluate the above relationship in the general population. Electronic databases (MEDLINE and EMBASE) were searched from January 2012 to May 2017 to identify English-language studies relevant to this review. Studies were included where influenza vaccination was explicitly reported as the dependent variable and SES as the independent variable. We limited our review to measures of SES that focus on education, income, social class, occupation, and deprivation. Studies that measured SES using other variables (e.g., race, ethnicity, geographic location, rural or urban status, or insurance status) were excluded. Studies were also excluded if they did not report on the human population or did not analyze original data. The population of interest included all age groups, levels of health status, and sociodemographic backgrounds. The review was also limited to World Bank high-income countries. Two authors independently screened full-text articles after obtaining a Kappa score of K = 0.867. The methodological quality of manuscripts was assessed using the appraisal tools developed by the Joanna Briggs Institute. Results were qualitatively reported and synthesized. RESULTS: Of the 42 articles included in this review, 52.4% (n = 22) found that higher levels of SES resulted in higher levels of influenza vaccination; 4.5% (n = 2) reported a negative association; and 14.3% (n = 6) found no association. Just over a quarter (26.2%, n = 12) of articles reported mixed results. CONCLUSIONS: There was consistently a relationship between SES and influenza immunization, which varied according to how SES was measured. It is recommended that authors be explicit in defining the SES concept they are trying to capture and that they utilize multiple measures of SES (e.g., education, income, class).

Impact of pharmacist administration of influenza vaccines on uptake in Canada.

BACKGROUND: Uptake of influenza vaccination in Canada remains suboptimal despite widespread public funding. To increase access, several provinces have implemented policies permitting pharmacists to administer influenza vaccines in community pharmacies. We examined the impact of such policies on the uptake of seasonal influenza vaccination in Canada. METHODS: We pooled data from the 2007-2014 cycles of the Canadian Community Health Survey (n = 481 526). To determine the impact of influenza vaccine administration by pharmacists, we estimated the prevalence ratio for the association between the presence of a pharmacist policy and individual-level vaccine uptake using a modified Poisson regression model (dependent variable: vaccine uptake) with normalized weights while controlling for numerous health and sociodemographic factors. RESULTS: Across all survey cycles combined, 28.8% of respondents reported receiving a seasonal influenza vaccine during the 12 months before survey participation. Introduction of a policy for pharmacist administration of influenza vaccine was associated with a modest increase in coverage (2.2%) and an individual's likelihood of uptake (adjusted prevalence ratio 1.05, 95% confidence interval 1.02-1.08). INTERPRETATION: Uptake of influenza immunization was modestly increased in Canadian jurisdictions that allowed pharmacists to administer influenza vaccines.

Epidemiology of pertussis in Alberta, Canada 2004-2015.

BACKGROUND: 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. METHODS: We 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. RESULTS: Over 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. CONCLUSION: Pertussis 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.

How well do ICD-9 physician claim diagnostic codes identify confirmed pertussis cases in Alberta, Canada? A Canadian Immunization Research Network (CIRN) Study.

BACKGROUND: Rates of Bordetella pertussis have been increasing in Alberta, Canada despite vaccination programs. Waning immunity from existing acellular component vaccines may be contributing to this. Vaccine effectiveness can be estimated using a variety of data sources including diagnostic codes from physician billing claims, public health records, reportable disease and laboratory databases. We sought to determine if diagnostic codes from billing claims (administrative data) are adequately sensitive and specific to identify pertussis cases among patients who had undergone disease-specific laboratory testing. METHODS: Data were extracted for 2004-2014 from a public health communicable disease database that contained data on patients under investigation for B. pertussis (both those who had laboratory tests and those who were epidemiologically linked to laboratory-confirmed cases) in Alberta, Canada. These were deterministically linked using a unique lifetime person identifier to the provincial billing claims database, which contains International Classification of Disease version 9 (ICD-9) diagnostic codes for physician visits. We examined visits within 90 days of laboratory testing. ICD-9 codes 033 (whooping cough), 033.0 (Bordetella pertussis), 033.1 (B. parapertussis), 033.8 (whooping cough, other specified organism), and 033.9 (whooping cough, other unspecified organism) in any of the three diagnostic fields for a claim were classified as being pertussis-specific codes. We calculated sensitivity, specificity, positive (PPV) and negative (NPV) predictive values. RESULTS: We identified 22,883 unique patients under investigation for B. pertussis. Of these, 22,095 underwent laboratory testing. Among those who had a laboratory test, 2360 tested positive for pertussis. The sensitivity of a pertussis-specific ICD-9 code for identifying a laboratory-confirmed case was 38.6%, specificity was 76.9%, PPV was 16.0%, and NPV was 91.6%. CONCLUSION: ICD-9 codes from physician billing claims data have low sensitivity and moderate specificity to identify laboratory-confirmed pertussis among persons tested for pertussis.

Live Attenuated Versus Inactivated Influenza Vaccine in Hutterite Children: A Cluster Randomized Blinded Trial.

BACKGROUND: Whether vaccinating children with intranasal live attenuated influenza vaccine (LAIV) is more effective than inactivated influenza vaccine (IIV) in providing both direct protection in vaccinated persons and herd protection in unvaccinated persons is uncertain. Hutterite colonies, where members live in close-knit, small rural communities in which influenza virus infection regularly occurs, offer an opportunity to address this question. OBJECTIVE: To determine whether vaccinating children and adolescents with LAIV provides better community protection than IIV. DESIGN: A cluster randomized blinded trial conducted between October 2012 and May 2015 over 3 influenza seasons. (ClinicalTrials.gov: NCT01653015). SETTING: 52 Hutterite colonies in Alberta and Saskatchewan, Canada. PARTICIPANTS: 1186 Canadian children and adolescents aged 36 months to 15 years who received the study vaccine and 3425 community members who did not. INTERVENTION: Children were randomly assigned according to community in a blinded manner to receive standard dosing of either trivalent LAIV or trivalent IIV. MEASUREMENTS: The primary outcome was reverse transcriptase polymerase chain reaction-confirmed influenza A or B virus in all participants (vaccinated children and persons who did not receive the study vaccine). RESULTS: Mean vaccine coverage among children in the LAIV group was 76.9% versus 72.3% in the IIV group. Influenza virus infection occurred at a rate of 5.3% (295 of 5560 person-years) in the LAIV group versus 5.2% (304 of 5810 person-years) in the IIV group. The hazard ratio comparing LAIV with IIV for influenza A or B virus was 1.03 (95% CI, 0.85 to 1.24). LIMITATION: The study was conducted in Hutterite communities, which may limit generalizability. CONCLUSION: Immunizing children with LAIV does not provide better community protection against influenza than IIV. PRIMARY FUNDING SOURCE: The Canadian Institutes for Health Research.

Prevalence and predictors of low serum 25-hydroxyvitamin D levels in rural Canadian children.

OBJECTIVES: Studies in Canada have reported varying prevalences of low serum 25-hydroxyvitamin D (25(OH)D) levels, but none have been conducted in rural paediatric populations. The purpose of this study was to determine the prevalence and predictors of low vitamin D levels in rural communities. METHODS: We conducted a cross-sectional study of children aged 3 to 15 living in Canadian Hutterite communities. Serum 25(OH)D levels were measured between October 2008 and April 2009 using a chemiluminescence assay. Predictors of vitamin D levels were evaluated using multivariable linear regression. A multilevel model was used to evaluate the impact of individual, household and colony factors on the variation in vitamin D levels. RESULTS: Serum 25(OH)D levels were available on 743 children/adolescents. The median was 62.0 nmol/L (interquartile range 51.0, 74.0). Levels lower than 50 nmol/L and 75 nmol/L were found in 152 (20.5%) and 565 (76%) children, respectively. Adolescents were at highest risk for levels <75 nmol/L (odds ratio 3.38, 95% confidence interval 2.00, 5.80). Age and latitude were negatively correlated with serum 25(OH)D level. In the multilevel model, most of the variation in levels was associated with individual children. CONCLUSION: Low vitamin D levels are a significant problem in rural Hutterite communities in Canada. Adolescents were at greatest risk for low levels and represent an important target group for supplementation. Variation in serum 25(OH)D levels was explained mostly at the individual level. Additional studies are needed to explore factors associated with individuals (e.g., genetics) leading to lower 25(OH)D levels.

HPV Vaccine utilization, Alberta 2008/09-2013/14 School year.

BACKGROUND: In Canada both bivalent (bHPV) vaccine and quadrivalent HPV vaccine (qHPV) are authorized for use. In Alberta, while both vaccines are available for private purchase, only qHPV is publicly funded for school girls in grades 5 and 9 as of 2013. We describe HPV vaccine uptake in Alberta, by school year, from the start of the publicly funded program in the Fall of 2008 through to August 31(st) 2014 and estimate the cumulative proportion of the female population who were vaccinated by the end of the 2013/14 school year. METHODS: We used data from the Alberta Ministry of Health Immunization and Adverse Reaction to Immunization repository (publicly funded vaccine), the population-based Pharmaceutical Information Network information systems (privately purchased vaccine) for the period September 1, 2008 to August 31, 2014 and demographic data from the Alberta Health Care Insurance Plan Registry. We estimate vaccine uptake rates and explore them by attributes of person, time, place, vaccine funding, and number of doses received. We estimated the cumulative proportions of the female population (by age group and number of doses received) who had received HPV vaccine by the end of the 2013/14 school year. RESULTS: Of the 169,259 unique individuals who received one or more doses of HPV vaccine over the period, 98.3% were females, and 83.8% received publicly funded vaccines. Vaccine uptake increased over the period. The cumulative proportion of females aged 9-26 years as of 2013/14 who had received two or more doses of vaccine was 34.3%; for those aged 10-11 years 59.6% and for those aged 14-15 years, 76.0%. For those aged 9-26 years, 31.3% had received three doses of vaccine. CONCLUSION: HPV vaccine uptake rates have increased in Alberta over the study period, most prominently among the age groups targeted by the publicly funded school-girl vaccine program.

How rural and urban parents describe convenience in the context of school-based influenza vaccination: a qualitative study.

BACKGROUND: Seasonal influenza vaccine uptake among school-age children has been low, particularly among rural children, even in jurisdictions in Canada where this immunization is publicly funded. Providing this vaccination at school may be convenient for parents and might contribute to increased vaccine uptake, particularly among rural children. We explore the construct of convenience as an advantage of school based influenza vaccination. We also explore for rural urban differences in this construct. METHODS: Participants were parents of school-aged children from Alberta, Canada. We qualitatively analyzed focus group data from rural parents using a thematic template that emerged from prior work with urban parents. Both groups of parents had participated in focus groups to explore their perspectives on the acceptability of adding an annual influenza immunization to the immunization program that is currently delivered in Alberta schools. Data from within the theme of 'convenience' from both rural and urban parents were then further explored for sub-themes within convenience. RESULTS: Data were obtained from nine rural and nine urban focus groups. The template of themes that had arisen from prior analysis of the urban data applied to the rural data. Convenience was a third level theme under Advantages. Five fourth level themes emerged from within convenience. Four of the five sub-themes were common to both rural and urban participants: reduction of parental burden to schedule, reduction in parental lost time, decrease in parental stress and increase in physical access points for influenza immunization. The fifth subtheme, increases temporal access to influenza immunization, emerged uniquely from the rural data. CONCLUSIONS: Both rural and urban parents perceived that convenience would be an advantage of adding an annual influenza immunization to the vaccinations currently given to Alberta children at school. Improving temporal access to such immunization may be a more relevant aspect of convenience to rural than to urban parents.

Herpes zoster vaccine (HZV): utilization and coverage 2009 - 2013, Alberta, Canada.

BACKGROUND: Herpes zoster vaccine (HZV) is not publicly funded in the province of Alberta, Canada. We estimated vaccine coverage among those aged 60 years or older for 2013, as well as vaccine utilization rates per hundred thousand population over the period 2009 - 2013. We explored for factors associated with HZV dispensing rates. METHODS: We used administrative data from the Alberta Pharmaceutical Information Network (PIN) database to identify unique persons for whom HZV had been dispensed from community pharmacies over 2009 - 2013. PIN data were also used to estimate the pharmacy/population ratios for rural and urban Alberta over the period. Denominators for rates were estimated using mid-year population estimates from the Alberta Health Care Insurance Plan Registry. Income quintile data were estimated from the 2006 Census of Canada. Crude, age, sex, geographic (rural vs. urban), income-quintile and year specific rates of HZV vaccine dispensing were estimated per 100,000 population. Rates were adjusted for pharmacy/population ratio. Vaccine coverage for persons aged 60 years or older was estimated using counts of all unique persons for whom the vaccine was dispensed over the period in the numerator and a 2013 mid- year population denominator. RESULTS: HZV dispensing rates rose annually from 2009 - 2013. Vaccine coverage was estimated to be 8.4% among persons aged 60 years or older. Rates of dispensing were highest for persons aged 60-69 years and were higher for females than males and for persons from higher compared to lower income quintiles. Dispensing rates were lower for rural than for urban residents. About 2% of vaccine was dispensed for persons aged less than 50 years. CONCLUSIONS: Rates of HZV dispensing are increasing rapidly in Alberta despite a lack of public funding. A small proportion of the vaccine may be dispensed off-label.

"I try to take all the time needed, even if i do not have it!": Knowledge, attitudes, practices of perinatal care providers in canada about vaccination.

Objective: Successful clinical conversations about vaccination in pregnancy (pertussis, COVID-19, and influenza) are key to improving low uptake rates of both vaccination in pregnancy and infancy. The purpose of this study was to understand Canadian perinatal care providers' knowledge, attitudes, and practices around vaccination in pregnancy. Methods: Qualitative interviews with 49 perinatal care providers (nurse practitioner, general practitioner, registered nurse, registered midwife, obstetrician-gynecologist, and family physicians) in 6 of 13 provinces and territories were deductively coded using directed content analysis [1] and analyzed according to key themes. Results: Participants detailed their professional training and experiences, patient community demographics, knowledge of vaccines, views and beliefs about vaccination in pregnancy, and attitudes about vaccine counselling. Providers generally described having a good range of information sources to keep vaccine knowledge up to date. Some providers lacked the necessary logistical setups to administer vaccines within their practice. Responses suggest diverging approaches to vaccine counselling. With merely hesitant patients, some opted to dig in and have more in-depth discussions, while others felt the likelihood of persuading an outright vaccine-refusing patient to vaccinate was too low to be worthwhile. Conclusion: Provider knowledge, attitudes, and practices around vaccination varied by professional background. To support perinatal providers' knowledge and practices, clinical guidelines should detail the importance of vaccination relative to other care priorities, emphasize the positive impact of engaging hesitant patients in vaccine counselling.

Low serum 25-hydroxyvitamin D level and risk of upper respiratory tract infection in children and adolescents.

BACKGROUND: Vitamin D may be important for immune function. Studies to date have shown an inconsistent association between vitamin D and infection with respiratory viruses. The purpose of this study was to determine if serum 25-hydroxyvitamin D (25(OH)D) was associated with laboratory-confirmed viral respiratory tract infections (RTIs) in children. METHODS: Serum 25(OH)D levels were measured at baseline and children from Canadian Hutterite communities were followed prospectively during the respiratory virus season. Nasopharyngeal specimens were obtained if symptoms developed and infections were confirmed using polymerase chain reaction. The association between serum 25(OH)D and time to laboratory-confirmed viral RTI was evaluated using a Cox proportional hazards model. RESULTS: Seven hundred forty-three children aged 3-15 years were followed between 22 December 2008 and 23 June 2009. The median serum 25(OH)D level was 62.0 nmol/L (interquartile range, 51.0-74.0). A total of 229 participants (31%) developed at least 1 laboratory-confirmed viral RTI. Younger age and lower serum 25(OH)D levels were associated with increased risk of viral RTI. Serum 25(OH)D levels <75 nmol/L increased the risk of viral RTI by 50% (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.10-2.07, P = .011) and levels <50 nmol/L increased the risk by 70% (HR, 1.67; 95% CI, 1.16-2.40, P = .006). CONCLUSIONS: Lower serum 25(OH)D levels were associated with increased risk of laboratory-confirmed viral RTI in children from Canadian Hutterite communities. Interventional studies evaluating the role of vitamin D supplementation to reduce the burden of viral RTIs are warranted.

The good, bad, and ugly of online recruitment of parents for health-related focus groups: lessons learned.

BACKGROUND: We describe our experiences with identifying and recruiting Ontario parents through the Internet, primarily, as well as other modes, for participation in focus groups about adding the influenza vaccine to school-based immunization programs. OBJECTIVE: Our objectives were to assess participation rates with and without incentives and software restrictions. We also plan to examine study response patterns of unique and multiple submissions and assess efficiency of each online advertising mode. METHODS: We used social media, deal forum websites, online classified ads, conventional mass media, and email lists to invite parents of school-aged children from Ontario, Canada to complete an online questionnaire to determine eligibility for focus groups. We compared responses and paradata when an incentive was provided and there were no software restrictions to the questionnaire (Period 1) to a period when only a single submission per Internet protocol (IP) address (ie, software restrictions invoked) was permitted and no incentive was provided (Period 2). We also compared the median time to complete a questionnaire, response patterns, and percentage of missing data between questionnaires classified as multiple submissions from the same Internet protocol (IP) address or email versus unique submissions. Efficiency was calculated as the total number of hours study personnel devoted to an advertising mode divided by the resultant number of unique eligible completed questionnaires . RESULTS: Of 1346 submitted questionnaires, 223 (16.6%) were incomplete and 34 (2.52%) did not meet the initial eligibility criteria. Of the remaining 1089 questionnaires, 246 (22.6%) were not from Ontario based on IP address and postal code, and 469 (43.1%) were submitted from the same IP address or email address (multiple submissions). In Period 2 vs Period 1, a larger proportion of questionnaires were submitted from Ontario (92.8%, 141/152 vs 75.1%, 702/937, P<.001), and a smaller proportion of same IP addresses (7.9%, 12/152 vs 47.1%, 441/937, P<.001) were received. Compared to those who made unique submissions, those who made multiple submissions spent less time per questionnaire (166 vs 215 seconds, P<.001), and had a higher percentage of missing data among their responses (15.0% vs 7.6%, P=.004). Advertisements posted on RedFlagDeals were the most efficient for recruitment (0.03 hours of staff time per questionnaire), whereas those placed on Twitter were the least efficient (3.64 hours of staff time per questionnaire). CONCLUSIONS: Using multiple online advertising strategies was effective for recruiting a large sample of participants in a relatively short period time with minimal resources. However, risks such as multiple submissions and potentially fraudulent information need to be considered. In our study, these problems were associated with providing an incentive for responding, and could have been partially avoided by activating restrictive software features for online questionnaires.

Longitudinal study of influenza molecular viral shedding in Hutterite communities.

BACKGROUND: The nature of influenza viral shedding during naturally acquired infection is not well understood. METHODS: A cohort study was conducted in Hutterite colonies in Alberta, Canada. Flocked nasal swabs were collected during 3 influenza seasons (2007-2008 to 2009-2010) from both symptomatic and asymptomatic individuals infected with influenza. Samples were tested by real-time reverse-transcription polymerase chain reaction for influenza A and influenza B, and the viral load (VL) was determined for influenza A positive samples. RESULTS: Eight hundred thirty-nine participants were included in the cohort; 25% (208) tested positive for influenza viruses. They experienced 238 episodes of viral shedding, of which 23 (10%) were not accompanied by symptoms. For seasonal and pandemic H1N1, VL peaked at or before onset of acute respiratory infection. For H3N2, VL peaked 2 days after the onset of acute respiratory infection, which corresponded to peaks in systemic and respiratory symptom scores. Although the duration of shedding was shorter for asymptomatic participants, the peak level of VL shedding was similar to that of symptomatic participants. Viral loads for children and adults revealed similar patterns. CONCLUSIONS: Molecular viral shedding values follow symptom scores, but timing of peak VL varies by subtype. Asymptomatic infections are infrequent.

A comparison of self-report and health care provider data to assess surveillance definitions of influenza-like illness in outpatients.

OBJECTIVE: Several surveillance definitions of influenza-like illness (ILI) have been proposed, based on the presence of symptoms. Symptom data can be obtained from patients, medical records, or both. Past research has found that agreements between health record data and self-report are variable depending on the specific symptom. Therefore, we aimed to explore the implications of using data on influenza symptoms extracted from medical records, similar data collected prospectively from outpatients, and the combined data from both sources as predictors of laboratory-confirmed influenza. METHODS: Using data from the Hutterite Influenza Prevention Study, we calculated: 1) the sensitivity, specificity and predictive values of individual symptoms within surveillance definitions; 2) how frequently surveillance definitions correlated to laboratory-confirmed influenza; and 3) the predictive value of surveillance definitions. RESULTS: Of the 176 participants with reports from participants and medical records, 142 (81%) were tested for influenza and 37 (26%) were PCR positive for influenza. Fever (alone) and fever combined with cough and/or sore throat were highly correlated with being PCR positive for influenza for all data sources. ILI surveillance definitions, based on symptom data from medical records only or from both medical records and self-report, were better predictors of laboratory-confirmed influenza with higher odds ratios and positive predictive values. DISCUSSION: The choice of data source to determine ILI will depend on the patient population, outcome of interest, availability of data source, and use for clinical decision making, research, or surveillance.

Suitable but requiring support: How the midwifery model of care offers opportunities to counsel the vaccine hesitant pregnant population.

Uptake of vaccination during pregnancy in Canada is lower than comparator countries. A recommendation from a trusted perinatal healthcare provider is a key opportunity to promote vaccine uptake and improve confidence. This study aims to identify barriers and opportunities to vaccination in midwifery care. Seventeen semi-structured telephone interviews with practicing midwives, educators and public health professionals with immunization training experiences were conducted. Documents pertaining to the midwifery profession (approx. 50) were reviewed. Inductive thematic analysis identified logistical, interprofessional, and information barriers preventing Canadian midwives from administering vaccines and counseling clients about vaccination, as well as opportunities to address each barrier. Key interventions at the level of logistics, training, and client information materials would help address barriers to the integration of midwives into the provision and recommendation of vaccines in perinatal care across Canada.

Exploring the reasons for low pertussis vaccine effectiveness in Ontario, Canada, 2006-2008: a Canadian Immunization Research Network study.

OBJECTIVES: Although pertussis vaccines have been widely used for many decades, a burden of illness persists. Resurgences in Ontario, Canada, have not been substantial in the past decade, but an outbreak of pertussis occurred in Toronto between 1 October 2005 and 31 March 2006. Previous Ontario studies found high vaccine effectiveness (VE) in the initial years post-immunization. In order to explore the impact of outbreaks and external factors on VE, we investigated pertussis VE during the period 2006-2008. METHODS: We assessed pertussis VE using a frequency-matched case-control study for the period 1 March 2006 to 31 December 2008. We used logistic regression to estimate VE by age, time since last vaccination, and vaccination status according to the Ontario recommended schedule. We compared analyses including and excluding cases from Toronto, and to two recent Ontario pertussis VE studies. RESULTS: We included 1797 confirmed cases and 7188 matched controls. Most cases were under 4 years of age during the study period. Pertussis VE was 3.8% (95% CI: - 21.0, 24.0) in the period 15-364 days following the last pertussis vaccine dose, and increased with increasing time since vaccination. Pertussis VE in the first 15-364 days excluding Toronto increased to 57.1% (95% CI: 26.0, 75.1), but the trend of increasing VE with time since vaccination persisted. Although VE was higher in older (6-11 years) than younger (0-5 years) children, it was lower at 12-13 years than after 14 years. CONCLUSION: VE was lower in comparison with other studies conducted in Ontario, particularly in younger children. Various factors occurring during the study period may have influenced the results, including clinical testing of asymptomatic contacts, laboratory testing and methods and reporting practice, and a sensitive case definition. Further studies are needed to optimize methods for measuring VE to inform pertussis vaccine policy.

RéSUMé: OBJECTIFS: Bien que les vaccins anticoquelucheux soient couramment utilisés depuis des dizaines d'années, la charge de morbidité de la coqueluche persiste. Sa réapparition en Ontario, au Canada, a été modérée au cours des 10 dernières années, mais une éclosion de coqueluche s'est produite à Toronto entre le 1er octobre 2005 et le 31 mars 2006. Des études antérieures menées en Ontario ont fait état d'une efficacité vaccinale (EV) élevée dans les premières années qui suivent l'immunisation. Pour explorer l'impact des éclosions et des facteurs externes sur l'EV, nous avons étudié l'efficacité des vaccins anticoquelucheux pour la période 2006-2008. MéTHODE: Nous avons évalué l'efficacité des vaccins anticoquelucheux à l'aide d'une étude cas-témoins assortie par fréquence pour la période du 1er mars 2006 au 31 décembre 2008. Nous avons procédé par régression logistique pour estimer l'EV selon l'âge, le temps écoulé depuis la dernière vaccination et le statut vaccinal d'après le calendrier recommandé en Ontario. Nous avons comparé les analyses en incluant et en excluant les cas de Toronto et par rapport à deux récentes études ontariennes sur l'efficacité des vaccins anticoquelucheux. RéSULTATS: Nous avons inclus 1 797 cas confirmés et 7 188 témoins assortis. La plupart des cas avaient moins de 4 ans durant la période de l'étude. L'efficacité des vaccins anticoquelucheux était de 3,8 % (IC de 95 % : -21,0, 24,0) au cours des 15 à 364 jours suivant la dernière dose de vaccin anticoquelucheux et augmentait avec le temps après la vaccination. En excluant Toronto, l'efficacité des vaccins anticoquelucheux au cours des 15 à 364 premiers jours passait à 57,1 % (IC de 95 % : 26,0, 75,1), mais la tendance d'augmentation de l'EV avec le temps après la vaccination était toujours présente. Bien que l'EV ait été supérieure chez les enfants plus vieux (6 à 11 ans) que chez les plus jeunes (0 à 5 ans), elle était plus faible chez les 12-13 ans qu'après 14 ans. CONCLUSION: Nous avons observé une EV plus faible que dans d'autres études menées en Ontario, surtout chez les jeunes enfants. Divers facteurs survenus durant la période de l'étude pourraient en avoir influencé les résultats, dont les tests cliniques menés sur les contacts asymptomatiques, les épreuves et les méthodes de laboratoire, les pratiques de déclaration et l'usage d'une définition de cas sensible. D'autres études sont nécessaires pour optimiser la méthode de mesure de l'EV afin d'éclairer la politique vaccinale contre la coqueluche.