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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., Competing Interests: Competing interests: MS is supported via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program and the Michael Smith Foundation for Health Research. MS has been an investigator on projects funded by GlaxoSmithKline, Merck, Pfizer, Sanofi-Pasteur, Seqirus, Symvivo and VBI Vaccines. All funds have been paid to his institute, and he has not received any personal payments. SEM is supported by a salary award from the Canadian Child Health Clinician Scientist Program., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The objective of this study was to estimate background rates of selected thromboembolic and coagulation disorders in Ontario, Canada., Design: Population-based retrospective observational study using linked health administrative databases. Records of hospitalisations and emergency department visits were searched to identify cases using International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada diagnostic codes., Participants: All Ontario residents., Primary Outcome Measures: Incidence rates of ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage, deep vein thrombosis, pulmonary embolism, idiopathic thrombocytopaenia, disseminated intravascular coagulation and cerebral venous thrombosis during five prepandemic years (2015-2019) and 2020., Results: The average annual population was 14 million with 51% female. The mean annual rates per 100 000 population during 2015-2019 were 127.1 (95% CI 126.2 to 127.9) for ischaemic stroke, 22.0 (95% CI 21.6 to 22.3) for intracerebral haemorrhage, 9.4 (95% CI 9.2 to 9.7) for subarachnoid haemorrhage, 86.8 (95% CI 86.1 to 87.5) for deep vein thrombosis, 63.7 (95% CI 63.1 to 64.3) for pulmonary embolism, 6.1 (95% CI 5.9 to 6.3) for idiopathic thrombocytopaenia, 1.6 (95% CI 1.5 to 1.7) for disseminated intravascular coagulation, and 1.5 (95% CI 1.4 to 1.6) for cerebral venous thrombosis. Rates were lower in 2020 than during the prepandemic years for ischaemic stroke, deep vein thrombosis and idiopathic thrombocytopaenia. Rates were generally consistent over time, except for pulmonary embolism, which increased from 57.1 to 68.5 per 100 000 between 2015 and 2019. Rates were higher for females than males for subarachnoid haemorrhage, pulmonary embolism and cerebral venous thrombosis, and vice versa for ischaemic stroke and intracerebral haemorrhage. Rates increased with age for most of these conditions, but idiopathic thrombocytopaenia demonstrated a bimodal distribution with incidence peaks at 0-19 years and ≥60 years., Conclusions: Our estimated background rates help contextualise observed events of these potential adverse events of special interest and to detect potential safety signals related to COVID-19 vaccines., Competing Interests: Competing interests: ‘Yes, there are competing interests for one or more authors and I have provided a Competing Interests statement in my manuscript and in the box below’, (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: In June 2015, Alberta, Canada instituted a universal publicly funded rotavirus vaccination programme (Rotarix, RV1), with vaccine doses scheduled for 2 and 4 months of age. Vaccination was restricted so that infants were only allowed to receive first dose between 6 and 20 weeks of age, and second dose before eight calendar months of age. We assessed the coverage and schedule non-compliance of rotavirus vaccination for babies born between June 2015 and August 2016, that is, since the inception of the publicly funded rotavirus vaccination programme, and determined factors associated with rotavirus vaccine uptake., Design: Retrospective cohort study using linked administrative health data., Setting: Alberta, Canada., Participants: Cohort of 66 689 children. PRIMARY AND SECONDARY OUTCOME MEASURES: (1) First and second dose rotavirus vaccination coverage, (2) percent of children non-compliant with recommended vaccine schedule and (3) adjusted ORs for factors associated with vaccination status., Results: For the 66 689 children included in the study, coverage levels for one-dose and two-dose rotavirus vaccination were 87% and 83%, respectively. In comparison, two-dose diphtheria-tetanus-pertussis-polio- Haemophilus influenzae type b vaccine coverage was 92%, despite having the same dosing schedule. Schedule non-compliance during the publicly funded programme was very low. We observed socioeconomic disparities in the uptake of the vaccine, with income, location of residence and number of children in the household all contributing to the odds of a child being vaccinated with rotavirus., Conclusions: Compliance to the recommended rotavirus schedule was very high, suggesting that even with the restrictive rotavirus vaccine schedule, the vaccine can be delivered on-time. However, rotavirus vaccine coverage remained lower than DTaP, a similarly scheduled childhood vaccination. We also observed socioeconomic disparities in vaccine uptake. These findings raise concerns about rotavirus protection in the groups at highest risk for gastrointestinal illness, including low-income and rural populations., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: Children may be placed in the care of the child welfare system when they require additional supports or intervention to ensure their safety and security. Transitions in living arrangements (eg, home to foster care and return to home) and other difficult circumstances for these children may result in interruptions in routine preventive healthcare, such as childhood immunisations. The purpose of this systematic literature review is to determine whether immunisation coverage is a problem among children in the child welfare system and identify any known supports and/or barriers to vaccine uptake in this population., Methods and Analysis: This systematic review will encompass published and unpublished primary research studies that assess (A) immunisation coverage of children in the child welfare system, (B) how this coverage compares to the general population and/or children not in the child welfare system, and (C) supports and barriers affecting immunisation status of these children. Vaccines in the recommended childhood immunisation schedule for each study setting will be considered. Medline, Embase, Cochrane Library, CINAHL, SocINDEX and ERIC will be comprehensively searched. We will also search ProQuest dissertations and theses, the Conference Proceedings Citation Index for Science and Social Science & Humanities, and a sample of relevant provincial, national and international websites. References of included studies will be manually searched for relevant studies. English language primary studies from 2000 to current focused on immunisations of children (age 0-17 years) in the child welfare system, in a high-income country, will be included. A narrative analysis of key findings from included studies will be performed and presented., Ethics and Dissemination: This protocol does not require ethics approval. Planned dissemination includes peer-reviewed publication, conference presentations and briefs for policy makers., Trial Registration Number: This protocol is registered in the PROSPERO International Prospective Register of Systematic Reviews, registration number CRD42016047319., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Background: Children under the age of 12 months may receive an early dose of measles-mumps-rubella (MMR) vaccine to provide short-term protection in the case of a disease outbreak. Following a measles outbreak in Alberta, Canada, there was concern that children who received an early dose may not be returning for their routinely scheduled dose at 12 months, leaving them vulnerable to disease in the long term., Methods: This population-based study of children born between 2006 and 2014 used administrative health data to assess coverage and timeliness of the first routine dose of MMR vaccine administered at age 12-24 months for children who received an early dose of the vaccine due to a disease outbreak. We compared this group to children who received an early dose due to travel to a measles-endemic region and to children who did not receive an early dose., Results: Only 5.5% of 366 351 children received an early dose. Coverage for the routine dose at age 24 months was 96.5% for children receiving an outbreak dose, 92.2% for those travelling to measles-endemic regions and 86.6% for those without an early dose (p<0.0001). The multivariable Cox proportional hazard analysis, controlling for neighbourhood income, place of residence and interaction effects, determined that, as compared to the general cohort, the outbreak group was most likely to obtain the first routine dose (adjusted HR (aHR): 1.52, 95% CI 1.44 to 1.60), followed by the travel group (aHR: 1.26, 95% CI 1.18 to 1.34)., Conclusions: It is reassuring that the majority of children who received an early dose returned for their routine dose and did so in a timely manner., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)