Population immunity to varicella in Canada: A Canadian Immunization Research Network (CIRN) study.

Introduction: The incidence of varicella in Canada has decreased by almost 99% since vaccination was introduced. However, variation in the timing and eligibility of vaccination programs across the country has resulted in some cohorts being under-vaccinated and therefore potentially susceptible to infection.

Methods: We used nationally representative specimens from the Biobank of Statistics Canada's Canadian Health Measures Survey (CHMS) as well as residual specimens from Ontario collected between 2009-2014 to estimate population immunity across age-groups and geography, and identify any groups at increased risk of varicella infection.

Prevalence of Oral Human Papillomavirus Infection Among Urban Gay, Bisexual, and Other Men Who Have Sex With Men in Canada, 2017-2019.

Background: Oral human papillomavirus (HPV) infections are a leading cause of oropharyngeal cancers. In 2015 and 2016, HPV vaccines became publicly funded for gay, bisexual, and other men who have sex with men (GBM) under 27 years of age in most Canadian provinces.

Methods: Between 2017 and 2019, sexually active GBM in Montreal, Toronto, and Vancouver were recruited through respondent-driven sampling.

SARS-CoV-2 seroprevalence in Nova Scotia blood donors.

Background: SARS-CoV-2 seroprevalence monitors cumulative infection rates irrespective of case testing protocols. We aimed to describe Nova Scotia blood donor seroprevalence in relation to public health policy and reported data over the course of the COVID-19 pandemic (May 2020 to August 2022).

Methods: Monthly random Nova Scotia blood donation samples (24,258 in total) were tested for SARS-CoV-2 infection antibodies (anti-nucleocapsid) from May 2020 to August 2022, and vaccination antibodies (anti-spike) from January 2021 to August 2022.

A National Advisory Committee on Immunization (NACI) update on invasive meningococcal disease (IMD) epidemiology and program-relevant considerations for preventing IMD in individuals at high risk of exposure.

Following recent outbreaks of invasive meningococcal disease (IMD) in Canada and updates to provincial vaccination guidelines, the National Advisory Committee on Immunization (NACI) conducted a targeted review of evidence with a focus on immunization of adolescents and young adults. NACI reviewed national and international immunization recommendations for populations at high-risk of IMD, national IMD epidemiology and program-relevant considerations. Given the varied IMD epidemiology, NACI determined that recommending a pan-Canadian targeted program is currently challenging and that regional programs may be better suited to prevent IMD in population groups considered to be at high-risk of exposure.

Uptake of pertussis immunization in pregnancy and determinants of vaccination in Toronto, Canada.

Introduction: Pertussis causes significant morbidity and mortality in infants aged <6 months. Maternal pertussis vaccination during pregnancy has been recommended in Canada since 2018 to reduce these negative outcomes. In the absence of routine immunization coverage data, our objective was to evaluate uptake in Toronto, Canada.

Canada's National Advisory Committee on immunization: Adaptations and challenges during the COVID-19 pandemic.

The COVID-19 pandemic has challenged traditional vaccine guidance infrastructure and frameworks, and added urgency and complexity to the operation of National Immunization Technical Advisory Groups (NITAGs). Canada's National Advisory Committee on Immunization (NACI) provides immunization guidance to the Public Health Agency of Canada (PHAC) who publicly shares expert and evidence-informed guidance with Canadian provinces and territories. Throughout the pandemic, NACI and PHAC implemented many adaptations to meet urgent needs for pandemic vaccine guidance.

Estimating the Incidence of First RSV Hospitalization in Children Born in Ontario, Canada.

Background: Respiratory syncytial virus (RSV) contributes significantly to morbidity in children, placing substantial burdens on health systems, thus RSV vaccine development and program implementation are a public health priority. More data on burden are needed by policymakers to identify priority populations and formulate prevention strategies as vaccines are developed and licensed.

Methods: Using health administrative data, we calculated incidence rates of RSV hospitalization in a population-based birth cohort of all children born over a six-year period (May 2009 to June 2015) in Ontario, Canada.

Self-reported Human Papillomavirus Vaccination and Vaccine Effectiveness Among Men Who Have Sex with Men: A Quantitative Bias Analysis.

Background: Self-report of human papillomavirus (HPV) vaccination has ~80-90% sensitivity and ~75-85% specificity. We measured the effect of nondifferential exposure misclassification associated with self-reported vaccination on vaccine effectiveness (VE) estimates.

Methods: Between 2017-2019, we recruited sexually active gay, bisexual, and other men who have sex with men aged 16-30 years in Canada.

Vaccine Effectiveness Against 12-Month Incident and Persistent Anal Human Papillomavirus Infection Among Gay, Bisexual, and Other Men Who Have Sex With Men.

Background: Real-world evidence of human papillomavirus (HPV) vaccine effectiveness (VE) against longitudinal outcomes is lacking among gay, bisexual, and other men who have sex with men (GBM). We compared 12-month incidence and persistence of anal HPV infection between vaccinated and unvaccinated GBM.

Methods: We recruited GBM aged 16-30 years in Montreal, Toronto, and Vancouver, Canada, from 2017 to 2019.

Increases in human papillomavirus vaccine coverage over 12 months among a community-recruited cohort of gay, bisexual, and other men who have sex with men in Canada.

Background: Starting in 2015/16, most Canadian provinces introduced publicly-funded human papillomavirus (HPV) vaccination programs for gay, bisexual, and other men who have sex with men (GBM) aged ≤ 26 years. We estimated 12-month changes in HPV vaccine coverage among community-recruited GBM from 2017 to 2021 and identified baseline factors associated with vaccine initiation (≥1 dose) or series completion (3 doses) among participants who were unvaccinated or partially vaccinated at baseline.

Methods: We recruited sexually-active GBM aged ≥ 16 years in Montreal, Toronto, and Vancouver, Canada, from 02/2017 to 08/2019 and followed them over a median of 12 months (interquartile range = 12-13 months).

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

We aimed to determine population immunity to measles in Canada, and to assess the risk of future outbreaks. We tested 11,176 sera from Cycles 2 (2009-2011) and 3 (2011-2013) cohorts from the biobank of Statistics Canada's Canadian Health Measures Survey (CHMS) using the BioPlex 2220 MMRV IgG assay. We then tested all BioPlex negative and equivocal samples using a more sensitive Plaque Reduction Neutralization Test (PRNT).

Assessment of population infection with SARS-CoV-2 in Ontario, Canada, March to June 2020.

BackgroundSerosurveys for SARS-CoV-2 aim to estimate the proportion of the population that has been infected.AimThis observational study assesses the seroprevalence of SARS-CoV-2 antibodies in Ontario, Canada during the first pandemic wave.MethodsUsing an orthogonal approach, we tested 8,902 residual specimens from the Public Health Ontario laboratory over three time periods during March-June 2020 and stratified results by age group, sex and region.

Anal Human Papillomavirus Prevalence Among Vaccinated and Unvaccinated Gay, Bisexual, and Other Men Who Have Sex With Men in Canada.

Background: Starting in 2015, human papillomavirus (HPV) vaccine has been publicly funded for gay, bisexual, and other men who have sex with men (GBM) 26 years or younger in Canada.

Methods: Self-identified GBM who reported having sex with another man within the past 6 months were enrolled using respondent-driven sampling (RDS) between February 2017 and August 2019 in Montreal, Toronto, and Vancouver, Canada. Men aged 16 to 30 years self-collected anal specimens for HPV-DNA testing.

Effectiveness of an outbreak dose of mumps-containing vaccine in two First Nations communities in Northern Ontario, Canada.

Between 18 Dec 2017 and 27 June 2018, a mumps outbreak occurred in two Canadian Indigenous communities. An outbreak dose of mumps-containing vaccine was offered as part of control measures. We conducted a cohort study and survival analysis to describe the outbreak and evaluate the outbreak dose, extracting vaccination information on all community members (n = 3,135) from vaccination records.

A multisite study of pertussis vaccine effectiveness by time since last vaccine dose from three Canadian provinces: A Canadian Immunization Research Network study.

Background: Pertussis remains poorly controlled relative to other diseases targeted by childhood vaccination programs. We combined estimates from four population-based studies of pertussis vaccine effectiveness (VE) in three Canadian provinces using a meta-analytic approach to improve precision and explore regional variation in VE and durability of protection.

Methods: Studies were conducted in Alberta, Manitoba, and Ontario over periods ranging from 1996 to 2015.

COVID-19 vaccination: Why extend the interval between doses?

On March 3, 2021, faced with ongoing morbidity and mortality from coronavirus disease 2019 (COVID-19) and insufficient supplies of authorized, available vaccines against COVID-19 in Canada, the National Advisory Committee on Immunization (NACI) issued a strong recommendation to allow for an extended interval between vaccine doses to maximize the number of people protected as quickly as possible. NACI's recommendation was released in the form of a rapid response because of the urgency of the situation and was based on a review of the evidence; principles of immunology; historical experience with vaccines; modelling studies; and consideration of ethics, equity, feasibility, and acceptability. Since then, many questions and concerns have been raised.

Vaccine coverage among children with epilepsy in two Canadian provinces: A Canadian immunization research network study.

Objectives: Children with epilepsy are at increased risk of complications from vaccine-preventable infections, yet information on vaccine coverage in these children is scarce. We aimed to compare vaccine coverage among children with epilepsy to children without epilepsy.

Study Design: We conducted a retrospective cohort study including all 2005-2013 births in Manitoba and Ontario, Canada, creating two cohorts: 2-year-olds and 7-year-olds (followed to age 2 and 7 years).

Herpes zoster in older adults in Ontario, 2002-2016: Investigating incidence and exploring equity.

Older adults are at increased risk of herpes zoster (HZ) and post-herpetic neuralgia (PHN) and HZ vaccines are available to help prevent infection. The objective of our study was to provide updated data on incidence of HZ and PHN related to clinical and demographic factors in older adults to inform immunization practices. We conducted a population-based, retrospective cohort study and included all cases of HZ seen in outpatient, emergency department, and hospital settings for adults aged 65 years and over between April 1, 2002 to August 31, 2016 in Ontario, Canada.

The geographic distribution of un-immunized children in Ontario, Canada: Hotspot detection using Bayesian spatial analysis.

Background: In Ontario, Canada, little is currently known about the extent to which un-immunized children may cluster geographically. Our objectives were to: describe the geographic distribution of fully un-immunized children; identify geographic clusters (hotspots) of un-immunized children; and to characterize the contribution of spatial effects and covariates on hotspots, where found.

Methods: Our analytic cohort consisted of Ontario students aged 7-17 years in the 2016-2017 school year.

SARS-CoV-2 Seroprevalence Survey Estimates Are Affected by Anti-Nucleocapsid Antibody Decline.

We analyzed 21 676 residual specimens from Ontario, Canada collected March-August 2020 to investigate the effect of antibody decline on SARS-CoV-2 seroprevalence estimates. Testing specimens orthogonally using Abbott (anti-nucleocapsid) and Ortho (anti-spike) assays, seroprevalence estimates were 0.4%-1.

"": a survey Ontario's school-based HPV immunization program ten years post-implementation.

Objectives: Describe Ontario's school-based human papillomavirus (HPV) vaccination program from the perspective of local public health units (PHUs).

Methods: In 2018, Vaccine Preventable Diseases (VPD) managers at each of Ontario's 35 PHUs were invited to participate in an online survey regarding the organization and delivery of their HPV vaccination program. Questions were asked on the school-based program, training and support of vaccine providers, communication and promotion, assessing coverage rates and perceptions of the program's strengths and challenges.