School-based vaccination program against HPV and Hepatitis B: A longitudinal analysis of vaccine coverage between 2015 and 2021 in Quebec.

BACKGROUND: HPV vaccination prevents cancers, including 90% of cervical cancer. Since 2008, a school-based HPV vaccination program has been implemented in Quebec, but vaccine coverage is suboptimal. The COVID-19 pandemic disrupted school-based vaccination programs. This study aimed to assess variation in HPV vaccination coverage in the school-based program between 2015 and 2022 in Quebec and to identify sociodemographic characteristics associated with non-vaccination. METHODS: HPV vaccine coverage data were extracted from the Quebec Immunization Registry for students in Grade 4 and matched to the 2016 Canadian census sociodemographic data. Descriptive analysis was conducted to explore individual-level vaccine coverage according to sociodemographic data. A Generalized Estimating Equations model assessed the independent association between non-vaccination and students' sociodemographic characteristics. RESULTS: HPV vaccine coverage (at least one dose) was 84% in 2018-2019 and 85% in 2019-2020. A decrease was observed during the pandemic. In 2020-2021, the HPV vaccine coverage (at least one dose) was 52% (at the end of the school year) and rose to 84% with intense catch-up activities. In 2021-2022, the coverage was slightly lower than before the pandemic (81%). Factors in the dissemination area were statistically significantly associated with non-vaccination: material (p-value = 0.0001) and social deprivation index (p-value = 0.0048), the proportion of immigration (p-value < 0.0001), and the language spoken at home (English (p-value = 0.0318), other than French or English (p-value = 0.0001). CONCLUSION: School-based vaccination programs offer equitable access to vaccination, and our analysis showed that some groups have consistently lower vaccine acceptance and uptake. Strategies to improve HPV vaccine coverage should target children living in areas with a higher proportion of immigrants, non-French speakers, and people from underprivileged backgrounds. Although it is too early to assess the full impact of COVID-19 on school-based programs in Quebec, it remains important to ensure that catch-up strategies are implemented for missed doses.

Neighborhood-level vaccine impact on COVID-19 infection and hospital admission in Quebec, Canada, during the Delta and early Omicron periods.

OBJECTIVE: To assess the impact of COVID-19 vaccination on COVID-19 infection and hospitalisation at the population-level, and to assess the indirect effects of vaccination in the province of Quebec, Canada. METHODS: We performed a time-stratified, neighborhood-level ecologic study. The exposure was neighborhood-level vaccination (primary series) coverage; outcomes were COVID-19 infection and hospitalisation rates. We used robust Poisson regression to estimate weekly relative rates of infection and hospitalisation versus vaccination. RESULTS: Higher vaccination coverage was associated with lower COVID-19 infection rates from July 18-December 4 for the year 2021 (Delta period) (RR≈0.46 [0.39; 0.54] - 0.94 [0.83; 1.05], 85-100% vs. 60-74% coverage). From December 5-December 25, this association reversed (RR≈1.28 [1.16; 1.41] - 1.41 [1.31; 1.52]), possibly due to the Omicron variant, social behaviors and accumulation of susceptibles in more vaccinated neighborhoods. Vaccine impact against hospitalisation was maintained throughout (RR≈0.43 [0.29; 0.65] - 0.88 [0.64; 1.22]). Vaccination provided substantial indirect protection (RR≈0.43 [0.34; 0.54] - 0.81 [0.65; 1.03]). CONCLUSIONS: This study confirmed the protective impact of vaccination against severe disease regardless of variant, at the population level. Ecological analyses are a valuable strategy to evaluate vaccination programs. Population-level effects can have substantial effects and should be accounted for in public health and vaccination program planning.

Sex differences in adverse events following seasonal influenza vaccines: a meta-analysis of randomised controlled trials.

BACKGROUND: Despite being a vaccine-preventable disease, influenza remains a major public health threat with vaccine safety concerns reducing vaccine acceptability. Immune responses to vaccines and adverse events may differ between males and females, but most studies do not report results by sex. Using data from clinical trials, we explored sex differences in adverse events following seasonal influenza vaccines. METHODS: We obtained data for phase III randomised controlled trials identified through a systematic review and clinical trials registries, and performed a two-stage meta-analysis. Risk ratios (RR) and 95% confidence intervals (95% CI) comparing solicited reactions in females versus males were pooled using the Mantel-Haenszel method and a random-effects model. We used the ROBINS-I tool to assess risk of bias and the I2 statistic for heterogeneity. Main analysis was stratified by age: 18-64 years and ≥65 years. RESULTS: The dataset for this analysis included 34 343 adults from 18 studies (12 with individual-level data and 6 with aggregate data). There was a higher risk of injection site reactions in females compared with males for both younger and older participants, with RRs of 1.29 (95% CI 1.21 to 1.37) and 1.43 (95% CI 1.28 to 1.60), respectively. Higher risk in females was also observed for systemic reactions, with RRs of 1.25 (95% CI 1.20 to 1.31) and 1.27 (95% CI 1.20 to 1.34) for younger and older participants, respectively. We also observed elevated risks of severe reactions in females, with a higher RR in younger versus older participants for systemic reactions (RRs 2.12 and 1.48, p=0.03, I2=79.7%). RRs were not found to vary between quadrivalent and trivalent vaccines. CONCLUSION: This meta-analysis suggested a higher risk of solicited reactions following influenza vaccines for females compared with males, irrespective of age and vaccine type. Transparent communication of this risk could increase the trust in vaccines and limit vaccine hesitancy. Future studies should report results stratified by sex and explore the role of gender in the occurrence of adverse events.

"The problem is not lack of information": A qualitative study of parents and school nurses' perceptions of barriers and potential solutions for HPV vaccination in schools.

BACKGROUND: HPV vaccination has been offered in school programs for over a decade in Quebec, Canada, but the vaccine coverages are not reaching the target coverage in several regions. This qualitative study aimed to describe barriers and enabling conditions of HPV vaccination as perceived by parents and school nurses and identify potential solutions to improve HPV vaccine uptake rates and acceptance in school-based programs. METHODS: Three focus group discussions were conducted with parents of children in Grades 2 or 3 who were unsure or unwilling to vaccinate. Individual interviews were conducted with 24 school nurses. A thematic content analysis was performed using N'Vivo. RESULTS: The main parental questions and concerns regarding the HPV vaccination were the children's young age, the possible side effects, the rationale behind boys' vaccination and the possible interaction with COVID-19 vaccination. Except for interaction with COVID-19 vaccination, these concerns remain similar to those identified before the pandemic. Interviews highlighted that the information on HPV vaccination provided by the public was not well understood by parents. Parents suggested different tools to access information tailored to their concerns and situation. From the nurses' perspective, HPV vaccination promotion tools such as decision-aids and social media communication campaigns were needed and could reduce their work. CONCLUSION: COVID-19 may have disrupted the acceptance of the vaccines. While strategies to catch up on missed doses and reduce access barriers to vaccines are urgently needed, our findings highlight that a shift in attitudes toward routine vaccines may pose further challenges even if HPV vaccine coverage appears to have returned to pre-pandemic levels.

Effectiveness of hospital-based strategies for improving childhood immunization coverage: A systematic review.

BACKGROUND: Hospital settings represent an opportunity to offer and/or promote childhood vaccination. The purpose of the systematic review was to assess the effectiveness of different hospital-based strategies for improving childhood vaccination coverage. METHODS: A systematic search of multiple bibliographic databases, thesis databases, and relevant websites was conducted to identify peer-reviewed articles published up to September 20, 2021. Articles were included if they evaluated the impact of a hospital (inpatient or emergency department)-based intervention on childhood vaccination coverage, were published in English or French, and were conducted in high-income countries. High quality studies were included in a narrative synthesis. RESULTS: We included 25 high quality studies out of 7,845 unique citations. Studies focused on routine, outbreak, and influenza vaccines, and interventions included opportunistic vaccination (i.e. vaccination during hospital visit) (n = 7), patient education (n = 2), community connection (n = 2), patient reminders (n = 2), and opportunistic vaccination combined with patient education and/or reminders (n = 12). Opportunistic vaccination interventions were generally successful at improving vaccine coverage, though results ranged from no impact to vaccinating 71 % of eligible children with routine vaccines and 9-61 % of eligible children with influenza vaccines. Interventions that aimed to increase vaccination after hospital discharge (community connection, patient education, reminders) were less successful. CONCLUSIONS: Some interventions that provide vaccination to children accessing hospitals improved vaccine coverage; however, the baseline coverage level of the population, as well as implementation strategies used impact success. There is limited evidence that interventions promoting vaccination after hospital discharge are more successful if they are tailored to the individual.

Impact of the first vaccine dose on COVID-19 and its complications in long-term care facilities and private residences for seniors in Québec, Canada.

Background: Residents of long-term care facilities (LTCFs) and private residences for seniors (PRSs) were given priority for vaccination against coronavirus disease 2019 (COVID-19). Given the shortage of vaccine in the winter of 2021, the Comité sur l'immunisation du Québec recommended postponing the administration of second doses to ensure more rapid and widespread administration of first doses. The objective of this study was to measure the impact of first-dose vaccination on 1) the incidence of cases and complications in LTCFs and PRSs and 2) the frequency of outbreaks in LTCFs. Methods: In this ecological study, COVID-19 incidence and complications in residents of LTCFs and PRSs in Québec were compared with the general (community) population at a point in time when there was still only limited eligibility for vaccination. Results: After vaccination in LTCFs, the incidence rate of COVID-19 decreased by 92% compared with 49% in the community, and deaths decreased by 95%. By six weeks post-vaccination, almost no facility reported five or more cases per 100 beds per week. The incidence rate decreased by 91% in PRSs compared with 2% in the community. Hospitalizations and deaths in PRSs decreased by 94% and 90%, respectively. Conclusion: As a result of 1) vaccination of residents with one dose, 2) natural immunity already acquired in LTCFs and PRSs, 3) vaccination of healthcare workers and 4) other non-pharmaceutical prevention measures implemented, the circulation of the coronavirus in these settings was largely interrupted.

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.

COVID-19 pandemic impact on childhood vaccination coverage in Quebec, Canada.

Response measures to mitigate the coronavirus disease 2019 pandemic impacted access to routine vaccination services. We evaluate the impact of the pandemic on routine infant vaccination uptake by comparing vaccination coverage, vaccine delays and doses administered in 2019 and 2020, in Quebec, Canada. Using a population-based vaccination registry, we compared vaccination coverage at 3, 5, 13 and 19 months of age between 2019 and 2020 cohorts each month from January to November. For vaccine delays, we measured the cumulative proportion vaccinated in each targeted cohort monthly. We also compared the measles-containing vaccines administered before 24 months of age between the same period in 2019 and 2020. A decline in vaccination coverage and children vaccinated on time was observed in all cohorts during the first months of the pandemic. The greatest impact was observed for the 18-month vaccination visit with a difference in vaccination coverage between both cohorts of 30.9% in May. Measles-containing doses administered during the first months of the pandemic were lower in 2020 compared with 2019: -21.1% in March (95%CI-21.6;-20.4), and -39.2% in April (95%CI-40.0;-38.2). After May, the coverage increased for all cohorts to reach pre-pandemic levels after a few months for most target ages. Routine childhood vaccinations were affected during the first months of the pandemic, but catch-up occurred thereafter and vaccination coverage in affected cohorts were very close to levels of 2019 after a few months of follow-up. Real-time monitoring of childhood vaccination is essential but also for other vaccination programs, severely affected by the pandemic.

Sexual behavior, clinical outcomes and attendance of cervical cancer screening by HPV vaccinated and unvaccinated sexually active women.

Concerns were raised about HPV vaccination possibly leading to riskier sexual behavior. We assessed sexual behaviors, risk of sexually transmitted infection, and attendance to cervical cancer screening by HPV vaccinated and unvaccinated young women. In this analysis, 1475 questionnaires completed by women aged 17-29 years were included. The majority of respondents (67.9%) were vaccinated against HPV. The proportion of those vaccinated decreased with age: from 93.2% in those aged 17-19 to 72.9% in those aged 20-22, and 21.8% in 23-29-year olds. A higher proportion of unvaccinated respondents had at least one sexual intercourse under the age of 15 when compared to those vaccinated (30% vs. 23%, p < .0001). The number of sexual partners during the last 12 months was similar between vaccinated and unvaccinated participants. Vaccinated participants reported more condom use (45% versus 38%; p = .0002), and less sexually transmitted infections (10% versus 28%; p < .0001), and less anogenital condylomas (2.2% vs. 11.6%; p < .0001). A screening test has been reported by 51% and 77% of vaccinated and unvaccinated participants, respectively (p < .0001). The association between vaccination status and cervical cancer screening disappeared when adjusting for participants' age. The study results consolidate the existing body of data regarding the absence of an impact of HPV vaccination on sexual behavior or use of contraceptives.

Outbreak investigation of SARS-CoV-2 transmission in an emergency childcare centre.

OBJECTIVE: To characterize SARS-CoV-2 transmission following a COVID-19 outbreak in an emergency childcare centre (ECCC) in April 2020 in Quebec, Canada. METHODS: The study population consisted of all the children and employees who attended the ECCC as well as household contacts of the confirmed COVID-19 cases. Of the 120 individuals in the study, five cases were confirmed by epidemiological link and 25 were identified as COVID-19 by RT-PCR among which 19 were analyzed by viral whole genome sequencing. Descriptive epidemiology, social network visualization, and phylogenetic analysis were used to characterize viral transmission. RESULTS: Phylogenetic analysis identified two separate introductions of distinct lineages of SARS-CoV-2 and estimated an average effective reproductive number of Re = 1.9 (range 0.9-4.9) with a mean doubling time of 3.2 days (range 2.1-5.2). The first and most prevalent lineage was introduced by two asymptomatic children who were likely infected by their parent, a confirmed COVID-19 case working in a long-term care centre. Among infected household adults, attack rates were significantly higher in mothers than in fathers (risk ratio = 4.5; 95% CI 1.1-18.7). The extent of transmission makes it one of the largest documented outbreaks in a daycare in Canada. CONCLUSION: The analyses carried out showed the probable origin and direction of the transmission of the infection (adult-child, child-adult, and child-child), thus highlighting how asymptomatic children can efficiently transmit SARS-CoV-2.

RéSUMé: OBJECTIF: Caractériser la transmission du SRAS-CoV-2 à la suite d'une éclosion de COVID-19 dans un service de garde d'urgence en milieu scolaire (SGUMS) en avril 2020 au Québec, Canada. MéTHODES: La population à l'étude était composée de tous les enfants et employés ayant fréquenté le SGUMS ainsi que les contacts familiaux des cas confirmés de COVID-19. Sur les 120 personnes à l'étude, cinq cas ont été confirmés par lien épidémiologique et 25 par RT-PCR. Parmi ces derniers, 19 ont été analysés par séquençage viral du génome entier. La caractérisation de la transmission a été réalisée à l'aide d'analyses descriptives et phylogénétiques ainsi que de la visualisation de réseaux sociaux. RéSULTATS: L'analyse phylogénétique a identifié deux introductions de lignées distinctes du SRAS-CoV-2 et un taux de reproduction net Re = 1,9 (étendue 0,9­4,9) avec un temps moyen de doublement de 3,2 jours (étendue 2,1­5,2). La première lignée, et la plus répandue, a été introduite par deux enfants asymptomatiques qui ont probablement été infectés par leur parent, un travailleur de la santé atteint de COVID-19. Dans les noyaux familiaux, les taux d'attaque étaient significativement plus élevés chez les mères que chez les pères (rapport de risque = 4,5 ; IC à 95 % 1,1­18,7). L'ampleur de la transmission en fait de celle-ci la plus importante éclosion documentée dans un service de garde au Canada. CONCLUSION: Cette étude a permis de déterminer l'origine et la direction probables de la transmission de l'infection (adulte-enfant, enfant-adulte et enfant-enfant) et démontrer que les enfants asymptomatiques peuvent transmettre le SRAS-CoV-2.

Participation in an action research project on vaccine services for children: relationship with vaccine delays.

Multicomponent interventions are effective in improving vaccine coverage. However, few studies have assessed their effect on timely vaccination. The aim of this study was to compare the proportion of children with vaccine delays at 2- and 12-month visits according to whether or not health centers have participated in an action research project on the organization of vaccination services for 0-5-year-olds. The action research project included a multicomponent intervention and was conducted between 2011 and 2015 in Quebec, Canada. An ecological before/after design was used for this analysis. A total of 264,579 DTaP-IPV-Hib (2-month visits) and 240,541 Men-C-C (12-month visits) vaccine doses were administered during 2011-2012 to 2014-2015 fiscal years, including 19% in 14 participating health centers and the remaining in 78 nonparticipating centers. Vaccine delays demonstrated a more pronounced decreasing trend in participating versus nonparticipating health centers (p < .0001 at 2 and 12 months). Between 2011-2012 and 2014-2015, participating centers managed to eliminate 35% of their vaccine delays at 2-month visits and 33% at 12-month visits, whereas nonparticipating centers eliminated 19% of delays at both visits. Our results are consistent with a positive impact of the multicomponent intervention, despite the fact that it had not specifically aimed at decreasing vaccine delays.

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.

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.

Investigation of an increase in large local reactions following vaccine schedule change to include DTaP-HB-IPV-Hib (Infanrix-hexa®) and MMRV (ProQuad®) at 18 months of age.

CONTEXT: In 2015 in Quebec, Canada, the passive vaccine adverse event reporting system detected an increase in large local reactions associated with vaccines recommended at the 18-month visit. This followed changes to the pediatric vaccine schedule to include hexavalent diphtheria-tetanus-acellular-pertusis-inactivated polio-Haemophilus influenzae type b-hepatitis B vaccine (DTaP-IPV-Hib-HB, Infanrix-hexa®, GSK) and quadrivalent measles-mumps-rubella-varicella vaccine (MMRV, ProQuad®, Merck) as 18-month booster doses. OBJECTIVES: To determine if the excess of large local reactions was caused by a specific vaccine or their co-administration in the same limb or during the same visit. METHODS: A case-control study was conducted among cases born between January 2012 and April 2015 with a large local reaction following MMR ±â€¯V or DTaP-IPV-Hib ±â€¯HB vaccines administered between 16 and 23 months of age. Controls were randomly selected from the provincial medicare database among children born during the same period. RESULTS: Our analysis included 96 cases and 494 controls vaccinated with MMRV or DTaP-IPV-Hib ±â€¯HB vaccines. Among the 96 cases, 46% had a cellulitis and 54% had an injection site reaction extending beyond the nearest joint and/or lasting ≥ 4 days. Among the 39 cases who were immunized in different limbs, 77% of the large local reactions were located at the Infanrix-hexa® site, 5% at the DTaP-IPV-Hib site and 18% at the ProQuad® site. Large local reactions were significantly more frequent with Infanrix-hexa® than with DTaP-IPV-Hib vaccine (OR 5.9 95% CI: 1.4-25.7). Administration of ProQuad® and Infanrix-hexa® in the same limb did not increase the risk of large local reactions. CONCLUSION: This investigation suggested that most large local reactions were causally associated with the Infanrix-hexa® vaccine and that the risk was not greater when ProQuad® and Infanrix-hexa® were administered in the same limb. Given the improved vaccine coverage for hepatitis B, benefit-risk analysis likely still favours ongoing use of Infanrix-hexa® with informed parental consent.

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.

Delayed measles vaccination of toddlers in Canada: Associated socio-demographic factors and parental knowledge, attitudes and beliefs.

Delaying vaccination increases the period of vulnerability of children against vaccine-preventable diseases. We used a nationally representative sample of Canadian two-year-old children to explore factors associated with delays in the uptake of the first dose of measles-containing vaccine, recommended in Canada for children at 12 months of age. Distribution of delays was determined using data from the 2013 Childhood National Immunization Coverage Survey. Logistic regression was used to examine sociodemographic factors and knowledge, attitudes and beliefs (KAB) associated with the two outcomes of interest: delays of one to six months (vaccination at 13 to 18 months of age) and delays of seven to 18 months (vaccination at 19 to 23 months of age). Overall, 69% (95% confidence interval [CI] 67-71) of children received their first valid dose on time. Twenty-nine percent (95% CI 27-31) and 11% (95% CI 9-12) of children were unvaccinated before turning 13 and 16 months of age, respectively. Factors associated with delays of one to six months were being a girl, being born outside Canada, and the jurisdiction of residence. Being from a single-parent family, being born outside Canada and the jurisdiction of residence were associated with delays of seven to 18 months, suggesting that potential barriers might be at play. Associations between KAB and vaccination delays indicate that vaccine hesitancy could contribute to measles vaccination delays in Canada. Barriers in accessing vaccination services and the role of vaccine hesitancy in timely vaccination must be better understood to reduce vaccination delays in toddlers in Canada.

Risk of Recurrence of Adverse Events Following Immunization: A Systematic Review.

CONTEXT: Reimmunizing patients who had an adverse event following immunization (AEFI) is sometimes a challenge because there are limited data on the risk and severity of AEFI recurrence. OBJECTIVE: To summarize the literature on the risk of AEFI recurrence. DATA SOURCES: PubMed, Embase, and Cochrane library. STUDY SELECTION: We included articles in English or French published before September 30, 2016. Articles were selected if they estimated the risk of AEFI recurrence in at least 5 individuals. Studies with experimental vaccines were excluded. DATA EXTRACTION: Data on study design, setting, population, vaccines, and AEFI recurrence were extracted. RESULTS: Twenty-nine articles were included. Among patients with a history of hypotonic hyporesponsive episode (n = 398), anaphylaxis (n = 133), or seizures (n = 60) who were reimmunized, events recurred in 0% to 0.8%. Allergic-like events recurred in 30 of 594 reimmunized patients. Fever recurred in 0% to 84% of 836 reimmunized patients, depending on the vaccine and dose number. Among children with extensive limb swelling after the fourth dose of diphtheria-tetanus-acellular pertussis vaccine, recurrence was higher when the fifth dose was given withthe full-antigen formulation (78%) compared with the reduced-antigen formulation (53%, P = .02) LIMITATIONS: Many studies, included few patients, and those with severe AEFIs were often not reimmunized. CONCLUSIONS: Despite vaccines being administered to millions of people annually, there are few studies in which researchers evaluated AEFI recurrence. Published studies suggest that reimmunization is usually safe. However in these studies, severe cases were often not reimmunized.

Acceptability of live attenuated influenza vaccine by vaccine providers in Quebec, Canada.

A live attenuated influenza vaccine (LAIV) was offered during the 2012-13 influenza season in Quebec, Canada, to children aged between 2 and 17 years with chronic medical conditions. Despite the offer, uptake of the vaccine was low. We assessed the perceptions and opinions about seasonal influenza vaccination and LAIV use among vaccine providers who participated in the 2012-13 campaign. More than 70% of them thought that LAIV was safe and effective and more than 90% considered that the vaccine was well-received by parents and healthcare professionals. According to respondents, the most frequent concerns of parents about LAIV were linked to vaccine efficacy. LAIV is well-accepted by vaccine providers involved in influenza vaccination clinics, but more information about the vaccine and the recommendations for its use are needed to increase vaccine uptake.

Seasonal influenza vaccination uptake in Quebec, Canada, 2 years after the influenza A(H1N1) pandemic.

BACKGROUND: A decrease in seasonal influenza vaccine uptake was observed after the influenza A(H1N1) pandemic in 2009. The goal of our study was to assess seasonal influenza vaccine uptake in 2011-2012, 2 years after the influenza A(H1N1) pandemic mass immunization campaign and to identify the main reasons for having or not having received the vaccine. METHODS: A telephone survey using random-digit dialing methodology was conducted. Case-weights were assigned to adjust for disproportionate sampling and for nonresponse bias. Descriptive statistics were generated for all variables. RESULTS: Seasonal influenza vaccine uptake was 57% among adults aged ≥60 years, 35% among adults with chronic medical conditions, and 44% among health care workers. The main reasons given for having been vaccinated were to be protected from influenza and a high perceived susceptibility to influenza, whereas low perceived susceptibility to influenza and low perceived severity of influenza were the main reasons for not having been vaccinated. CONCLUSIONS: An increase in seasonal influenza vaccine uptake was observed 2 years after the influenza A(H1N1) pandemic. However, vaccine coverage is still below the target level of 80%. More efforts are needed to develop effective strategies to increase seasonal influenza vaccine uptake.