Single-Dose Messenger RNA Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 in Healthcare Workers Extending 16 Weeks Postvaccination: A Test-Negative Design From Québec, Canada.

BACKGROUND: In Canada, first and second doses of messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were uniquely spaced 16 weeks apart. We estimated 1- and 2-dose mRNA vaccine effectiveness (VE) among healthcare workers (HCWs) in Québec, Canada, including protection against varying outcome severity, variants of concern (VOCs), and the stability of single-dose protection up to 16 weeks postvaccination. METHODS: A test-negative design compared vaccination among SARS-CoV-2 test-positive and weekly matched (10:1), randomly sampled, test-negative HCWs using linked surveillance and immunization databases. Vaccine status was defined by 1 dose ≥14 days or 2 doses ≥7 days before illness onset or specimen collection. Adjusted VE was estimated by conditional logistic regression. RESULTS: Primary analysis included 5316 cases and 53 160 controls. Single-dose VE was 70% (95% confidence interval [CI], 68%-73%) against SARS-CoV-2 infection; 73% (95% CI, 71%-75%) against illness; and 97% (95% CI, 92%-99%) against hospitalization. Two-dose VE was 86% (95% CI, 81%-90%) and 93% (95% CI, 89%-95%), respectively, with no hospitalizations. VE was higher for non-VOCs than VOCs (73% Alpha) among single-dose recipients but not 2-dose recipients. Across 16 weeks, no decline in single-dose VE was observed, with appropriate stratification based upon prioritized vaccination determined by higher vs lower likelihood of direct patient contact. CONCLUSIONS: One mRNA vaccine dose provided substantial and sustained protection to HCWs extending at least 4 months postvaccination. In circumstances of vaccine shortage, delaying the second dose may be a pertinent public health strategy.

Promoting vaccination in the province of Québec: the PromoVaQ randomized controlled trial protocol.

BACKGROUND: Vaccination has a huge public health impact. Maintaining vaccine coverage is key to avoid the devastating consequences of resurgence. In the Province of Québec, vaccine coverage in young children are sub-optimal, mostly due to ambivalence toward vaccine safety and efficacy. We previously conducted a regional study in the Québec's Eastern Townships region, the PromoVac Study, to test a new educational intervention, based on motivational interviewing techniques, aimed at promoting infant vaccination. This first study evidenced that the intervention led to a marked increase in mothers' intention to vaccinate, and vaccine coverage in their infants. The current study protocol aims at scaling up these results at a provincial level using a randomized controlled trial design. METHODS: This pragmatic, randomized, controlled, parallel-group clinical trial will compare the effectiveness of the motivational interviewing to an educational intervention, including the distribution of an information flyer as standard of care on vaccination coverage in four maternity wards across the Province of Québec (PromovaQ). Adult mothers of children born in participating maternity wards were recruited between March 2014 and February 2015. Vaccination coverage will be assessed at 3-years of age, thus the trial is expected to be completed in March 2019. Statistical analyses will be conducted under the intention-to-treat principle. Vaccine coverage will be analyzed using Chi-squared distribution testing and logistic regression to identify determinant factors. Secondary outcomes will include vaccine hesitation and intention scores, mother's knowledge, attitudes and beliefs about immunization, and psychosocial determinants of intention to vaccinate. DISCUSSION: In the case results of this Provincial RCT be confirmed, serious consideration should then be given by Ministry of Health authorities to the possible implementation of MI-based strategies across provincial maternity wards. To ensure adequate input and secure implementation, study design and results will be reviewed with relevant stakeholders, including the children's families, and provincial and regional decision-makers. Results will be adapted and shared with all stakeholders. TRIAL REGISTRATION: ClinicalTrials.gov NCT02666872 (Retrospectively registered as January 28, 2016).

Promoting vaccination in maternity wards ─ motivational interview technique reduces hesitancy and enhances intention to vaccinate, results from a multicentre non-controlled pre- and post-intervention RCT-nested study, Quebec, March 2014 to February 2015.

BackgroundMany countries are grappling with growing numbers of parents who delay or refuse recommended vaccinations for their children. This has created a need for strategies to address vaccine hesitancy (VH) and better support parental decision-making regarding vaccination.AimTo assess vaccination intention (VI) and VH among parents who received an individual motivational-interview (MI) based intervention on infant immunisation during post-partum stay at a maternity ward between March 2014 and February 2015.MethodsThis non-controlled pre-/post-intervention study was conducted using the results from parents enrolled in the intervention arm of the PromoVaQ randomised control trial (RCT), which was conducted in four maternity wards across the Province of Quebec. Participants (n = 1,223) completed pre- and post-intervention questionnaires on VI and VH using Opel's score. Pre-/post-intervention measures were compared using McNemar's test for categorical variables and Wilcoxon signed-rank test for continuous variables.ResultsPre-intervention: overall VI was 78% and significantly differed across maternity wards (74%, 77%, 84%, 79%, p = 0.02). Post-intervention: VI rose significantly across maternity wards (89%, 85%, 95%, 93%) and the overall increase in VI was 12% (78% vs 90%, p < 0.0001). VH corroborated these observations, pre- vs post-intervention, for each maternity ward (28% vs 16%, 29% vs 21%, 27% vs 17%, 24% vs 13%). Overall, VH was curbed post-intervention by 40% (27% vs 16%; p < 0.0001).ConclusionsCompared with pre-intervention status, participants who received the MI-based intervention on immunisation displayed lower hesitancy and greater intention to vaccinate their infant at 2 months of age.

Impact of vaccine delays at the 2, 4, 6 and 12 month visits on incomplete vaccination status by 24 months of age in Quebec, Canada.

BACKGROUND: Timeliness in the administration of recommended vaccines is often evaluated using vaccine delays and provides more information regarding the susceptibility of children to vaccine-preventable diseases compared with vaccine coverage at a given age. The importance of on-time administration of vaccines scheduled at the first visit is well documented, but data are scarce about the impact of vaccine delays at other visits on vaccination status by 24 months of age. Using vaccine delays for the first three doses of DTaP-containing vaccines and for the first dose of measles-containing vaccines as markers of timeliness at the 2, 4, 6 and 12 month visits, we estimated the proportion of incomplete vaccination status by 24 months of age attributable to a vaccine delay at each of these visits. METHODS: We used the data from six cross-sectional coverage surveys conducted in the Province of Quebec from 2006 to 2016 which included 7183 children randomly selected from the universal health insurance database. A vaccine dose was considered delayed if received 30 days or more after the recommended age. The impact of new vaccine delays at each visit on incomplete vaccination status by 24 months of age was estimated with the attributable risk in the population. RESULTS: The proportion of children with vaccine delay was 5.4% at 2 months, 13.3% at 4 months, 23.1% at 6 months and 23.6% at 12 months. Overall, 72.5% of all 2-year-old children with an incomplete status by 24 months were attributable with a vaccine delay, of which 16.1% were attributable with a first vaccine delay at 2 months, 10.6% at 4 months, 14.0% at 6 months and 31.8% at 12 months. CONCLUSIONS: While great emphasis has been put on vaccine delays at the first vaccination visit, the prevalence of vaccine delays was greater with later visits and most children with an incomplete vaccination status by 24 months had a vaccine delay occurring during these later visits. Interventions to improve timeliness should address vaccine delays at each visit and not only focus on the first visit.

Impact of an Immunization Campaign to Control an Increased Incidence of Serogroup B Meningococcal Disease in One Region of Quebec, Canada.

Background: Invasive meningococcal disease (IMD) incidence increased in Quebec, starting in 2003, and was caused by a serogroup B sequence type 269 clone. The Saguenay-Lac-Saint-Jean (SLSJ) region was particularly affected with a rate of 3.4 per 100000 person-years in 2006-2013. In May 2014, an immunization campaign was launched in SLSJ, using the 4-component protein-based meningococcal vaccine (MenB-4C). We aimed to evaluate the impact of the campaign 2 years after its initiation. Methods: Immunization registry data and serogroup B invasive meningococcal disease (B-IMD) cases notified to public health authorities and confirmed by culture or polymerase chain reaction from July 1996 to December 2016 were analyzed, including a multivariate Poisson regression model of incidence rates. Results: By the end of the campaign, 82% of the 59000 targeted SLSJ residents between 2 months and 20 years of age had been immunized. Following the initiation of the campaign, no B-IMD case occurred among vaccinees, whereas 2 cases were reported among unvaccinated adult SLSJ residents, and a third case in an unvaccinated child who had stayed in the region during the week prior to disease onset, in 2015. B-IMD incidence decreased in all other regions in the years 2015-2016 but sporadic cases continued to occur. A multivariate analysis showed a significant effect of the campaign in the SLSJ region (relative B-IMD risk: 0.22; P = .04). Conclusions: Results suggest a high level of protection provided by MenB-4C following mass vaccination at regional level. This, along with reassuring safety data, supports the current recommendations for MenB-4C use for controlling outbreaks caused by clones covered by the vaccine.

Parents' and adolescents' willingness to be vaccinated against serogroup B meningococcal disease during a mass vaccination in Saguenay-Lac-St-Jean (Quebec).

A mass vaccination campaign with the 4CMenB vaccine (Bexsero®; Novartis Pharmaceutical Canada Inc) was launched in a serogroup B endemic area in Quebec. A telephone survey was conducted to assess parental and adolescent opinions about the acceptability of the vaccine. Intent to receive the vaccine or vaccine receipt was reported by the majority of parents (93%) and adolescents (75%). Meningitis was perceived as being a dangerous disease by the majority of parents and adolescents. The majority of respondents also considered the 4CMenB vaccine to be safe and effective. The main reason for positive vaccination intention or behaviour was self-protection, while a negative attitude toward vaccination in general was the main reason mentioned by parents who did not intend to have their child vaccinated. Adolescents mainly reported lack of interest, time or information, and low perceived susceptibility and disease severity as the main reasons for not intending to be vaccinated or not being vaccinated.

Une campagne de vaccination de masse avec le vaccin 4CMenB (Bexsero®; Novartis Pharma Canada Inc.) a été lancée dans une région du Québec endémique au sérogroupe B. Un sondage téléphonique afin d'évaluer l'acceptabilité du vaccin par les parents et les adolescents a été réalisé. La majorité des parents (93 %) et des adolescents (75 %) ont déclaré avoir l'intention de se faire vacciner / de faire vacciner leur enfant ou l'avoir déjà fait. La majorité des parents et des adolescents percevaient la méningite comme dangereuse et considéraient le vaccin 4CMenB comme sécuritaire et efficace. La protection de l'enfant était la principale raison d'accepter le vaccin chez les parents, tandis qu'une attitude négative envers la vaccination en général était la principale raison que donnaient les parents qui n'avaient pas l'intention de faire vacciner leur enfant. Les adolescents déclaraient surtout un manque d'intérêt, de temps ou d'information, la perception d'être peu susceptibles à la maladie et la perception que la maladie n'était pas très grave comme principales raisons de ne pas s'être fait vacciner ou de ne pas avoir l'intention de le faire.

Largest measles epidemic in North America in a decade--Quebec, Canada, 2011: contribution of susceptibility, serendipity, and superspreading events.

BACKGROUND: The largest measles epidemic in North America in the last decade, occurred in 2011 in Quebec, Canada, where rates of 1- and 2-dose vaccine coverage among children 3 years of age were 95%-97% and 90%, respectively, with 3%-5% unvaccinated. METHODS: Case patients identified through passive surveillance and outbreak investigation were contacted to determine clinical course, vaccination status, and possible source of infection. RESULTS: There were 21 measles importations and 725 cases. A superspreading event triggered by 1 importation resulted in sustained transmission and 678 cases. The overall incidence was 9.1 per 100,000; the highest incidence was in adolescents 12-17 years old (75.6 per 100,000), who comprised 56% of case patients. Among adolescents, 22% had received 2 vaccine doses. Outbreak investigation showed this proportion to have been an underestimate; active case finding identified 130% more cases among 2-dose recipients. Two-dose recipients had milder illness and a significantly lower risk of hospitalization than those who were unvaccinated or single-dose recipients. CONCLUSIONS: A chance superspreading event revealed an overall level of immunity barely above the elimination threshold when unexpected vulnerability in 2-dose recipients was taken into account. Unvaccinated individuals remain the immunization priority, but a better understanding of susceptibility in 2-dose recipients is needed to define effective interventions if elimination is to be achieved.

Higher risk of measles when the first dose of a 2-dose schedule of measles vaccine is given at 12-14 months versus 15 months of age.

BACKGROUND: In 2011, >750 cases of measles were reported in Quebec, Canada, where a routine 2-dose measles immunization schedule, in which measles vaccine is given at 12 and 18 months of age, had been in effect since 1996. Effectiveness of this schedule was assessed during a high school outbreak. METHODS: Cases were identified by passive followed by active surveillance. Classical cases met the national surveillance definition; attenuated cases showed clinical signs and high measles-specific immunoglobulin G but did not fulfill all classical criteria. Immunization status was ascertained from written records, and vaccine effectiveness (VE) was calculated as 1 - [(risk of measles in vaccinated individuals)/(risk in unvaccinated individuals)] × 100%. RESULTS: Among 1306 students, 110 measles cases were identified; 98 were classical cases, and 12 were attenuated cases. The attack rates among unvaccinated and fully vaccinated students were 82% and 4.8%, respectively. The VE among 2-dose recipients was 95.5% against classical and 94.2% against all (classical + attenuated) measles. Among 2-dose recipients, attack rates with first immunization at 12 and ≥15 months of age were 5.8% and 2.0%, respectively, with corresponding VE values of 93.0% and 97.5%. The risk of measles in 2-dose recipients was significantly (3-4-fold) higher when vaccine was first administered at 12 months of age, compared with ≥15 months of age (P = .04). CONCLUSIONS: Despite compliance with the recommended 2-dose measles immunization schedule, 6% of high school students were susceptible during this outbreak. Residual susceptibility was 2-4-fold higher among 2-dose recipients who had received the first dose of vaccine prior to 15 months of age. If confirmed in other settings, these results suggest that administration of the first dose of measles vaccine before 15 months of age may not be optimal for measles elimination efforts.

Risk of Guillain-Barré syndrome following H1N1 influenza vaccination in Quebec.

CONTEXT: In fall 2009 in Quebec, Canada, an immunization campaign was launched against the 2009 influenza A(H1N1) pandemic strain, mostly using an AS03 adjuvant vaccine. By the end of the year, 57% of the 7.8 million residents had been vaccinated. OBJECTIVE: To assess the risk of Guillain-Barré syndrome (GBS) following pandemic influenza vaccine administration. DESIGN: Population-based cohort study with follow-up over the 6-month period October 2009 through March 2010. The investigation was ordered by the chief medical officer of health in accordance with the Quebec Public Health Act. SETTING: All acute care hospitals and neurology clinics in Quebec. POPULATION: Suspected and confirmed GBS cases reported by physicians, mostly neurologists, during active surveillance or identified in the provincial hospital summary discharge database. Medical records were reviewed and cases classified according to Brighton Collaboration definitions (categorized as level 1, 2, or 3, corresponding to criteria of decreasing certainty in diagnosis). Immunization status was verified and denominators were estimated from the provincial immunization registry (4.4 million vaccinated) and census data (total target population aged ≥6 months, 7.8 million), with a total of 3,623,046 person-years of observation. MAIN OUTCOME MEASURES: Relative and attributable risks were calculated using a Poisson model and the self-controlled case-series method. RESULTS: Over a 6-month period, 83 confirmed GBS cases were identified, including 71 Brighton level 1 through 3 cases. Twenty-five confirmed cases had been vaccinated against 2009 influenza A(H1N1) 8 or fewer weeks before disease onset, with most (19/25) vaccinated 4 or fewer weeks before onset. In the Poisson model, the age- and sex-adjusted relative risk was 1.80 (95% CI, 1.12-2.87) for all confirmed cases during the 8-week postvaccination period and was 2.75 (95% CI, 1.63-4.62) during the 4-week postvaccination period. Using the self-controlled case-series method, relative risk estimates during the 4-week postvaccination period were 3.02 (95% CI, 1.64-5.56) for all confirmed cases (n = 42) and 2.33 (95% CI, 1.19-4.57) for Brighton level 1 through 3 cases (n = 36). The number of GBS cases attributable to vaccination was approximately 2 per 1 million doses. There was no indication of an excess risk in persons younger than 50 years. CONCLUSIONS: In Quebec, the 2009 influenza A(H1N1) vaccine was associated with a small but significant risk of GBS. It is likely that the benefits of immunization outweigh the risks.

Acute otitis media and its prevention by immunization: a survey of Canadian pediatricians' knowledge, attitudes and beliefs.

INTRODUCTION: Acute otitis media (AOM) is one of the most common bacterial infectious diseases among children and is a leading cause of child healthcare visits and antibiotic prescriptions. Few vaccines have the potential to prevent AOM. The newer pneumococcal conjugate vaccines (PCV) offer a larger spectrum of protection against AOM, as well as preventing severe diseases. The main aim of this study was to assess pediatricians' opinions regarding AOM and its prevention by immunization. RESULTS: Response rate was 50%. Around 60% of respondents estimated that more than 50% of their patients under the age of 3 years would suffer from at least one episode of AOM in the following year. Most respondents (79%) rated consequences of AOM as moderate. Almost all physicians (99%) considered the newer PCV as safe and effective. Most respondents considered their knowledge of the new vaccines was sufficient. More than 90% had a firm intention to recommend newer PCV to their patients. Perceived benefits of AOM prevention by immunization were: reduction of antibiotic administration and reduction of post-AOM complications. More than half of respondents (53%) considered the risk of adverse events as a barrier to AOM prevention by immunization. In multivariate analysis, the main determinant of pediatricians' intention to recommend newer PCV was perceived safety and efficacy of the vaccines (partial R2 = 0.40, p < 0.0001). DISCUSSION: Results of this survey show that AOM is perceived as an important health problem by paediatricians. Information about the increased protection against AOM offered by newer PCV should be disseminated to physicians. MATERIALS AND METHODS: A self-administered, anonymous, mail-based questionnaire based upon the Health Belief Model and the Analytical framework for immunization programs was sent to all 1,852 Canadian pediatricians.

Burden of acute otitis media on Canadian families.

OBJECTIVE: To estimate the burden of acute otitis media (AOM) on Canadian families. DESIGN: Telephone survey using random-digit dialing. SETTING: All Canadian provinces between May and June 2008. PARTICIPANTS: Caregivers of 1 or more children aged 6 months to 5 years. MAIN OUTCOME MEASURES: Caregivers' reports on the number of AOM episodes experienced by the child in the past 12 months, as well as disease characteristics, health services and medication use, time spent on medical consultations (including travel), and time taken off from work to care for the sick children. RESULTS: A total of 502 eligible caregivers were recruited, 161 (32%) of whom reported at least 1 AOM episode for their children and 42 (8%) of whom reported 3 or more episodes during the past 12 months. Most children (94%, 151 of 161) visited with health professionals during their most recent AOM episodes. The average time required for medical examination was 3.1 hours in an emergency department and 1.8 hours in an outpatient clinic. Overall, 93% of episodes resulted in antibiotics use. A substantial proportion of caregivers (38%) missed work during this time; the average time taken off work was 15.9 hours. CONCLUSION: In Canada, episodes of AOM are still associated with substantial use of health services and indirect costs to the caregivers.

Contagious period for pandemic (H1N1) 2009.

We estimated the proportion of persons with pandemic (H1N1) 2009 who were shedding infectious virus at diagnosis and on day 8 of illness. In households with confirmed cases, nasopharyngeal swabs were collected on all members and tested by PCR and virus culture. Of 47 cases confirmed by PCR at <7 days of illness, virus culture was positive in 92% (11/12) of febrile and 63% (22/35) of afebrile persons. Of 43 persons with PCR-confirmed pandemic (H1N1) 2009 from whom a second specimen was collected on day 8, 74% remained PCR positive and 19% were culture positive. If the 73 symptomatic household members without PCR-confirmed illness are assumed to have pandemic (H1N1) 2009, a minimum of 8% (6/73) of case-patients shed replicating virus on day 8. Self-isolation only until fever abates appears insufficient to limit transmission. Self-isolation for a week may be more effective, although some case-patients still would shed infectious virus.

Association between the 2008-09 seasonal influenza vaccine and pandemic H1N1 illness during Spring-Summer 2009: four observational studies from Canada.

BACKGROUND: In late spring 2009, concern was raised in Canada that prior vaccination with the 2008-09 trivalent inactivated influenza vaccine (TIV) was associated with increased risk of pandemic influenza A (H1N1) (pH1N1) illness. Several epidemiologic investigations were conducted through the summer to assess this putative association. STUDIES INCLUDED: (1) test-negative case-control design based on Canada's sentinel vaccine effectiveness monitoring system in British Columbia, Alberta, Ontario, and Quebec; (2) conventional case-control design using population controls in Quebec; (3) test-negative case-control design in Ontario; and (4) prospective household transmission (cohort) study in Quebec. Logistic regression was used to estimate odds ratios for TIV effect on community- or hospital-based laboratory-confirmed seasonal or pH1N1 influenza cases compared to controls with restriction, stratification, and adjustment for covariates including combinations of age, sex, comorbidity, timeliness of medical visit, prior physician visits, and/or health care worker (HCW) status. For the prospective study risk ratios were computed. Based on the sentinel study of 672 cases and 857 controls, 2008-09 TIV was associated with statistically significant protection against seasonal influenza (odds ratio 0.44, 95% CI 0.33-0.59). In contrast, estimates from the sentinel and three other observational studies, involving a total of 1,226 laboratory-confirmed pH1N1 cases and 1,505 controls, indicated that prior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009, with estimated risk or odds ratios ranging from 1.4 to 2.5. Risk of pH1N1 hospitalization was not further increased among vaccinated people when comparing hospitalized to community cases. CONCLUSIONS: Prior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009 in Canada. The occurrence of bias (selection, information) or confounding cannot be ruled out. Further experimental and epidemiological assessment is warranted. Possible biological mechanisms and immunoepidemiologic implications are considered.

Antibody and immune memory persistence after vaccination of preadolescents with low doses of recombinant hepatitis B vaccine.

Little is known about the impact of low-dose hepatitis B vaccine on the persistence of anti-HBs and immune memory in school-age children. Recombivax-HB 2.5 µg (RB) has been widely used in school-age children. RB induces high seroprotectionrates, but relatively low anti-HBs titers. The main objectives of this phase of the study were to assess anti-HBs persistence and the presence of immune memory 10 years post-vaccination of 8-10 year-old children with 3 doses of RB and the persistence of anti-HBs post-booster dose administration 5 (Group A; n=250) or 10 years (Group B; n=263) post-vaccination. No significant difference was observed between GMTs and the proportion of subjects with anti-HBs titers ≥ 10 mIU/mL 5 or 10 years post-vaccination. In both groups, a 56-fold decrease of anti-HBs GMTs was observed. One month post-booster, all but two subjects in Group A had an anti-HBs titer ≥ 10 mIU/mL. A 4.9- and 11.4-fold decrease in anti-HBs GMTs were observed during the first year post-booster in Group A and B, respectively. One year post-booster, the two groups were equivalent: ≥ 98.8% of subjects had an anti-HBs ≥ 10 mIU/mL. In group A, five years post-booster, 96.8% had a titer ≥ 10 mIU/mL; the GMT was 17-fold higher than the GMT 5 years post-vaccination (p<0.0001). In both groups, there was a strong positive correlation (p<0.0001) between anti-HBs titers observed post-primary vaccination and at following study time points (r=0.70-0.90). Three doses of RB administered at the age of 8-10 years induce a 10 years long-lasting immunity in virtually all vaccinees. The booster does not appear necessary on a 10 years perspective.

Children vaccination coverage surveys: Impact of multiple sources of information and multiple contact attempts.

BACKGROUND: Monitoring vaccination coverage is an essential component of vaccination program evaluation. In Québec (Canada), children vaccination coverage surveys are conducted every two years since 2006. The objectives of this study were to evaluate the impact of supplementing data based on vaccination booklets with data from vaccine providers, on the final estimated vaccination coverage and to compare vaccination coverage between respondents to each survey contact attempt. METHODS: Data from six cross-sectional surveys were used, which included 3508 children aged 2 years. Parents were invited to transcribe the information available in their child's vaccination booklet on the questionnaire received by mail. The survey included a maximum of 4 contact attempts to obtain a response. Data were completed among vaccine providers identified by parents. The main outcome was a complete vaccination status by 24 months of age. RESULTS: The addition of data from vaccine providers to those present in vaccination booklets increased the proportion of children fully vaccinated from 5.5% to 23.7% depending on the survey year. The proportion of children fully vaccinated by 24 months of age estimated among respondents to contact 1 was only 2.1% higher than the estimates among all respondents. CONCLUSIONS: Without validation among vaccine providers for children with missing doses according to vaccination booklets, results underestimated vaccination coverage in the target population. Conducting multiple contact attempts increased the response rate but had limited impact on the validity of estimates. It would be useful in future surveys to present the coverage obtain from respondents to each contact attempt.

Uptake of pneumococcal conjugate vaccine: methodological issues in measurement and impact of publicly funded programs.

BACKGROUND: In Quebec, the pneumococcal conjugate vaccine was available on the private market as early as 2001 and has been included in the publicly funded immunization program since December 2004. OBJECTIVES: To compare the advantages and limitations of two different sources for assessing vaccination coverage in the target population of children and to evaluate the impact of the public health program on uptake rates. METHODS: Data from a province-wide survey of a random sample of parents and from the Quebec City Immunization Registry were used to compute vaccination rates over time in different population groups. RESULTS: Data from the immunization survey and the regional registry were congruent regarding trends. Immunization rates were overestimated, more in the registry than in the survey. During the 2001-2004 period, uptake rates were low, and many children received fewer than the recommended number of doses. As soon as free vaccination was granted, uptake increased markedly and close to 90% of children received the recommended three doses, the level required for inducing herd effects. Delay in the administration of the third booster dose was observed. CONCLUSIONS: Free vaccination is a major determinant of vaccine uptake and should remain a fundamental principle of the Canadian health system.

Cervical cancer prevention by vaccination: nurses' knowledge, attitudes and intentions.

AIM: This paper is a report of a survey: (1) to document nurses' knowledge, attitudes and information needs regarding human papillomavirus prevention and (2) to determine factors associated with their willingness to recommend human papillomavirus vaccines. BACKGROUND: Persistent infection with human papillomavirus has been causally linked to cervical cancer. Two human papillomavirus vaccines have recently been approved for use in more than 65 countries. Nurses' level of support for the prevention of human papillomavirus related diseases by vaccination has not been researched. METHODS: A survey was conducted in 2007. Self-administered questionnaires were mailed to 1799 randomly selected nurses. Descriptive statistics were generated for all variables. Multivariable logistic regression models were estimated to determine variables associated with the willingness to recommend human papillomavirus vaccines. RESULTS: A total of 946 questionnaires were analyzed and showed that: 97% of nurses perceived routinely recommended vaccines as very useful; 93% would support human papillomavirus vaccination if it is publicly funded; 85% would recommend human papillomavirus vaccines to their patients; 33%, 46% and 61% expect the vaccination to permit screening to begin later in life, reduction of the frequency of screening, and reduction of the number of postscreening interventions, respectively. Respondents' knowledge score was 3.8 out of 7. Several modifiable factors, including knowledge, perceived self-efficacy, and societal and colleagues support were associated with willingness to recommend vaccines. CONCLUSION: Most nurses' support human papillomavirus vaccination, but their active involvement should not be taken for granted. Targeted educational efforts are needed to ensure nurses' involvement in the prevention of human papillomavirus-related diseases.

Overview of knowledge, attitudes, beliefs, vaccine hesitancy and vaccine acceptance among mothers of infants in Quebec, Canada.

BACKGROUND: Vaccine hesitancy (VH) is a growing problem. The first step in addressing VH is to have an understanding of who are the hesitant individuals and what are their specific concerns. The aim of this survey was to assess mothers' level of vaccine hesitancy and vaccination knowledge, attitudes, and beliefs. METHODS: Mothers of newly-born infants in four maternity wards in Quebec (Canada) completed a self-administered questionnaire. The questionnaire included items to assess VH and intention to vaccinate. VH scores were calculated using the Parents Attitudes about Childhood Vaccines (PACV) survey. Multivariate logistic regression was performed to determine variables associated with intention to vaccinate (OR; 95% CI). RESULTS: Overall, 2645 questionnaires were included in this analysis and 77.5% of respondents certainly intended to vaccinate their infant at 2 months of age. Based on the PACV 100-point scale, 56.4% of mothers had a 0 to ˂30 score (low level of VH); 28.6% had a 30 to ˂50 and 15.0% had a score of 50 and higher (high level of VH).The main determinants of mothers' intention to vaccinate were the perceived importance of vaccinating infants at 2 months of age (OR = 9.2; 5.9-14.5) and a low score of VH (OR = 7.4; 5.3-10.3). DISCUSSION: Although the majority of mothers held positive attitudes toward vaccination, a large proportion were moderately or highly vaccine hesitant. Mothers' level of VH was strongly associated with their intention to vaccinate their infants, showing the potential detrimental impact of VH on vaccine uptake rates and the importance of addressing this phenomenon.

Absence of association between Guillain-Barré syndrome hospitalizations and HPV-vaccine.

BACKGROUND: In 2008, a school-based human papilloma virus (HPV) vaccination program was implemented in the province of Québec. Grade 4 girls (9-10 years old) are routinely vaccinated and grade 9 to 12 girls (14-17 years old) were eligible for the catch-up vaccination. Vaccine coverage of the targeted cohorts was estimated at 76-81%. To assess if HPV vaccination is associated with an increase in GBS hospitalisation, we compared the hospitalization rates of GBS in HPV vaccination targeted and non-targeted groups. METHODS: Hospital discharge records with a GBS code as the main diagnosis during the 1999-2014 period were retrieved. Incidence rates according to program eligibility were computed and adjusted relative risk in the targeted groups was estimated by Poisson regression. RESULTS: The overall incidence rate in the 7 to 17 year-olds was 0.73/100,000 p-y. There was no increase in GBS incidence in HPV vaccination targeted groups (adjusted IRR = 0.81, 95%CI: 0.29-2.26). CONCLUSION: No signal of increase GBS hospitalisation incidence in the HPV-vaccine targeted group was detected in the hospitalisation database.

Impact of the addition of new vaccines in the early childhood schedule on vaccine coverage by 24 months of age from 2006 to 2016 in Quebec, Canada.

CONTEXT: Between 2004 and 2016, in the province of Quebec (Canada), 4 new antigens were added in the early childhood vaccine schedule from birth to 18 months, increasing the number of injections or doses needed from 7 to 12. These additions may have decreased the proportion of children who had received all recommended vaccines. OBJECTIVES: To assess the impact of the introduction of new vaccines to the childhood schedule on the 24-month vaccine coverage from 2006 to 2016 and identify factors associated with incomplete vaccination status by 24 months of age. METHODS: We used the data from six cross-sectional vaccine coverage surveys conducted every two years which included a total of 3515 children aged 2 years old and randomly selected from the Quebec public health insurance database. Factors associated with an incomplete vaccine status by 24 months were identified with multivariable logistic regression. RESULTS: Despite the addition of 4 new vaccine antigens since 2004, the vaccine coverage remained high from 2006 (82.4%) through 2016 (88.3%) for vaccines present in the schedule since 2006. In 2016, vaccine coverage was 78.2% for all vaccines included in the schedule. The vaccine coverage of new vaccines increases rapidly within 2 years of their introduction. For both new and older vaccines, incomplete vaccine status by 24 months of age is associated with a delay of 30 days or more in receiving the vaccines scheduled at 2 and 12 months of age. CONCLUSIONS: Increasing to 12 the number of doses in the recommended schedule has slightly reduced the vaccine coverage by 24 months of age and the vaccine coverage of vaccines already in the schedule remained stable over the years. Future additions to the vaccine schedule may not be similarly accepted by the population and this will require continuing the monitoring of vaccine coverage.