Summary of the National Advisory Committee on Immunization (NACI) statement on the prevention of respiratory syncytial virus (RSV) in older adults.

Background: Respiratory syncytial virus (RSV) is a common respiratory virus. In addition to infants, older adults are at higher risk of severe outcomes due to RSV, particularly advanced-age older adults and those with chronic medical conditions. The authorization of three vaccines, one for adults 50 years of age and older (Arexvy) and two for adults 60 years of age and older (Abrysvo and mRESVIA), offers the opportunity to protect older Canadians from RSV disease.

Monovalent mRNA XBB.1.5 vaccine effectiveness against COVID-19 hospitalization in Quebec, Canada: Impact of variant replacement and waning protection during 10-month follow-up.

Background: Vaccine formulations targeting contemporaneous subvariants have been developed to respond to SARS-CoV-2 virus evolution. Updated monovalent COVID-19 vaccines targeting the Omicron XBB.1.

Summary of the National Advisory Committee on Immunization (NACI) Statement on the Prevention of Respiratory Syncytial Virus (RSV) in Infants.

Background: Immunization programs for the prevention of respiratory syncytial virus (RSV) in infants have been available in Canada since the authorization of palivizumab in 2002. However, these programs have been limited to only those infants at highest risk for severe RSV disease. The authorization of new passive immunizing products to prevent RSV, including a new monoclonal antibody (nirsevimab) and a vaccine administered in pregnancy (RSV pre-fusion stabilized F protein; RSVpreF) offers the opportunity to prevent RSV in more Canadian infants.

Factors influencing acceptance of RSV immunization for newborns among pregnant individuals: A mixed-methods study.

Background: Respiratory syncytial virus (RSV) is a major cause of respiratory infections and hospitalizations in Canadian infants. Recently, Health Canada approved two novel immunizing products: a vaccine given during pregnancy and a monoclonal antibody for infants. This study assessed knowledge, attitudes, and intentions regarding RSV and its prevention among pregnant individuals.

Impact of SARS-CoV-2 vaccination and of seasonal variations on the innate immune inflammatory response.

Introduction: The innate immune response is an important first checkpoint in the evolution of an infection. Although adaptive immunity is generally considered the immune component that retains antigenic memory, innate immune responses can also be affected by previous stimulations. This study evaluated the impact of vaccination on innate cell activation by TLR7/8 agonist R848, as well as seasonal variations.

Burden of disease of respiratory syncytial virus in older adults and adults considered at high risk of severe infection.

Background: Availability of new vaccines for adults has increased interest in understanding Canada's respiratory syncytial virus (RSV) burden in older adults and adults considered at high risk of severe infection.

Objective: To characterize the burden of RSV disease in Canada by joint analysis of the published literature and hospitalization data from a healthcare administrative database.

Methods: Electronic databases of published literature were searched to identify studies and systematic reviews reporting data on outpatient visits, hospitalizations, intensive care unit (ICU) admissions and deaths associated with RSV infection in adults.

Infection Rate and Risk Factors of SARS-CoV-2 Infection in Retail Workers at the Onset of the COVID-19 Pandemic, Quebec, Canada.

During the pandemic, client-facing workers were perceived to be at greater risk of SARS-CoV-2 infection. This study investigated the risk factors for SARS-CoV-2 infection among a cohort of 304 retail workers in the Quebec City metropolitan area. After providing consent, participants were interviewed to gather information on demographic, socioeconomic, behavioural, and occupational variables.

Effectiveness of the ten- and thirteen-valent pneumococcal conjugate vaccines to prevent serotype 19A invasive pneumococcal disease in Quebec, Canada. A Canadian immunization research network (CIRN) study.

In the province of Quebec, Canada, a 2 + 1 dose pneumococcal conjugate vaccine (PCV) program for children was implemented in 2004. PCV7, PCV10, PCV13 and a mixed PCV10/PCV13 schedule were sequentially used without catch-up. The effectiveness of vaccination schedules to prevent serotype 19A invasive pneumococcal disease (IPD) in <5-year-old children was estimated by the indirect cohort method during 2009-2023.

Respiratory syncytial virus vaccination strategies for older Canadian adults: a cost-utility analysis.

Background: Respiratory syncytial virus (RSV) vaccines could reduce disease burden and costs in older Canadian adults, but vaccination program cost-effectiveness is unknown. We evaluated the cost-effectiveness of different age cut-offs for RSV adult vaccination programs, with or without a focus on people with higher disease risk due to chronic medical conditions.

Methods: We developed a static individual-based model of medically attended RSV disease to compare alternative age-, medical risk-, and age-plus medical risk-based vaccination policies.

Live virus neutralizing antibodies against pre and post Omicron strains in food and retail workers in Québec, Canada.

Background: Measuring the ability of SARS-CoV-2 antibodies to neutralize live viruses remains an effective approach to quantify the level of protection of individuals. We assessed the neutralization activity against the ancestral SARS-CoV-2, Delta, Omicron BA.1, BA.

Burden of disease of respiratory syncytial virus in infants, young children and pregnant women and people.

Background: Passive immunization products for infants and pregnant women and people have sparked interest in understanding Canada's respiratory syncytial virus (RSV) burden. This rapid review examines RSV burden of disease in infants, young children and pregnant women and people.

Methods: Electronic databases were searched to identify studies and systematic reviews reporting data on outpatient visits, hospitalizations, intensive care unit admissions, deaths and preterm labour associated with RSV.

Vaccination during pregnancy and modulation of IgG response to pertussis vaccines in infants: The impact of different vaccine formulations.

The IgG response following infant diphtheria-tetanus-acellular pertussis (DTaP) immunization is influenced by the formulation of the infant and/or the adult vaccine (Tdap) given during pregnancy. DTaP vaccines containing either 3 (DTaP3) or 5 (DTaP5) pertussis antigens are commonly used. By conducting a secondary analysis of a large randomized controlled trial, we compared IgG levels against pertussis vaccine antigens in children of Td- and Tdap5-vaccinated mothers, after stratifying by infant vaccine formulation.

The safety of seasonal influenza vaccination among adults prescribed immune checkpoint inhibitors: A self-controlled case series study using administrative data.

Background: Immune checkpoint inhibitor (ICI) therapy for patients undergoing cancer treatment carries a risk of severe immune-related adverse events (IRAEs). Questions remain about whether seasonal influenza vaccination might increase the risk of developing IRAEs among these patients given that vaccines are immunomodulatory. Previous vaccine safety studies on patients with cancer prescribed ICI therapy have demonstrated conflicting results.

Antenatal tetanus, diphtheria, and acellular pertussis (Tdap) immunization and risk of serogroup 19 IPD in children: An indirect cohort study.

The tetanus-diphtheria-acellular pertussis (Tdap) vaccine has been indicated for pregnant women in Quebec, Canada since 2018. Recent literature suggests maternal Tdap interferes with the pneumococcal vaccine response in children exposed in utero because of maternally transferred anti-diphtheria antibodies, a phenomenon known as blunting. Using an indirect cohort study, we investigated whether maternal Tdap vaccination could alter the protection of PCV vaccines against serotype 19A/F IPD (conjugated to diphtheria toxoid in PCV10).

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.

Tdap vaccine in pregnancy and immunogenicity of pertussis and pneumococcal vaccines in children: What is the impact of different immunization schedules?

Background: In 2019, the 3 + 1 schedule for children's vaccination (2-4-6-18 months old) was changed for a reduced 2 + 1 schedule (2-4-12 months old) in Quebec, Canada. We compared the post-booster anti-pertussis and anti-pneumococcus IgG antibody concentrations among children of Tdap-vaccinated and unvaccinated mothers for different vaccine schedules and vaccine formulations.

Methods: We conducted an observational cohort study.

Clonal diversity of Streptococcus pneumoniae serotype 19A collected from children < 5 years old in Québec, Canada, 2016-2021.

Streptococcus pneumoniae serotype 19A is a highly diverse, often antimicrobial-resistant Gram-positive bacterium which can cause invasive pneumococcal disease (IPD). In 2021, public health authorities in the Canadian province of Québec observed an increase of serotype 19A IPD in children <5 years. The purpose of this study was to determine the clonal composition of serotype 19A isolates collected from this age group in Québec, from 2016 to 2021.

Effectiveness of thirteen-valent pneumococcal conjugate vaccine to prevent serotype 3 invasive pneumococcal disease in Quebec in children, Canada.

In the province of Quebec, Canada, a 2 + 1 dose pneumococcal conjugate vaccine (PCV) program for children was implemented in 2004. PCV7 was replaced by PCV10 in 2009, by PCV13 in 2011 and by PCV10 in 2018, without catch-up in all instances. The objective was to estimate PCV13 effectiveness to prevent serotype 3 invasive pneumococcal disease in children aged less than 5 years, using 2010-2018 mandatory notification and laboratory surveillance data, an indirect cohort design and multivariate logistic regression models.

Effectiveness of previous infection-induced and vaccine-induced protection against hospitalisation due to omicron BA subvariants in older adults: a test-negative, case-control study in Quebec, Canada.

Background: Older adults (aged ≥60 years) were prioritised for COVID-19 booster vaccination due to severe outcome risk, but the risk for this group is also affected by previous SARS-CoV-2 infection and vaccination. We estimated vaccine effectiveness against omicron-associated hospitalisation in older adults by previously documented infection, time since last immunological event, and age group.

Methods: This was a population-based test-negative case-control study done in Quebec, Canada, during BA.

Summary of the National Advisory Committee on Immunization (NACI) Rapid Response-Interim guidance on the use of Imvamune in the context of monkeypox outbreaks in Canada.

Background: Monkeypox is endemic in Central and West Africa. Cases in non-endemic countries, including Canada, have been increasing since May 2022. Imvamune, a live, non-replicating smallpox vaccine, was approved by Health Canada for active immunization against smallpox and monkeypox infections and disease in adults determined to be at high risk for exposure.

Increase of invasive pneumococcal disease in children temporally associated with RSV outbreak in Quebec: a time-series analysis.

Background: Respiratory viruses have been previously suspected to trigger invasive pneumococcal disease (IPD). After progressive non-pharmaceutical interventions (NPI) lifting, an unusual RSV outbreak has been observed in the Fall 2021, raising concerns about the possible consequences on IPD. We aimed to analyse the evolution of IPD incidence across age-groups since NPI lifting, and its temporal association with respiratory viral infections.

Summary of the National Advisory Committee on Immunization (NACI) Rapid Response: Updated interim guidance on Imvamune in the context of ongoing monkeypox outbreaks.

Background: During the period of monkeypox community transmission and restricted vaccine supply in the summer of 2022, Canadian provinces and territories and a number of vaccine stakeholders indicated the need for consistent national guidance on pre-exposure vaccination (including the identification of priority populations for pre-exposure vaccination programs) and guidance on the potential use of dose-sparing strategies.

Methods: The National Advisory Committee on Immunization (NACI) High Consequence Infectious Disease Working Group reviewed data on the status of the monkeypox outbreak along with additional published and non-published evidence regarding the safety, immunogenicity and protection offered by Imvamune. NACI approved updated recommendations on September 16, 2022, and on September 23, 2022 it released updated interim guidance on the use of Imvamune in the context of the ongoing monkeypox outbreak.

Estimated Protection of Prior SARS-CoV-2 Infection Against Reinfection With the Omicron Variant Among Messenger RNA-Vaccinated and Nonvaccinated Individuals in Quebec, Canada.

Importance: The Omicron variant is phylogenetically and antigenically distinct from earlier SARS-CoV-2 variants and the original vaccine strain. Protection conferred by prior SARS-CoV-2 infection against Omicron reinfection, with and without vaccination, requires quantification.

Objective: To estimate the protection against Omicron reinfection and hospitalization conferred by prior heterologous non-Omicron SARS-CoV-2 infection and/or up to 3 doses of an ancestral, Wuhan-like messenger RNA (mRNA) vaccine.