Gap analyses to assess Canadian readiness for respiratory syncytial virus vaccines: Report from an expert retreat

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. We also contacted Canadian respiratory virus surveillance experts for additional data.

Results

Overall, 17 studies on infants and young children and 10 studies on pregnant women and people were included, in addition to primary surveillance data from one Canadian territory (Yukon). There were higher rates of medical utilization for infants than older children. Hospitalization rates were highest in infants under six months (more than 1% annually), with 5% needing intensive care unit admission, but mortality was low. Severe outcomes often occurred in healthy full-term infants and burden was higher than influenza. Respiratory syncytial virus attack rate was 10%-13% among pregnant women and people. Only one study found a higher hospitalization rate in pregnant women and people compared to non-pregnant women and people. Limited evidence was found on intensive care unit admission, death and preterm birth for pregnant women and people.

Conclusion

While risk of severe outcomes is larger in high-risk infants and children, healthcare burden is greatest in healthy term infants. The RSV severity for pregnant women and people appears to be similar to that for non-pregnant women and people.

Burden of illness associated with Respiratory Syncytial Virus (RSV)-related hospitalizations among adults in Ontario, Canada: A retrospective population-based study

BACKGROUND

Globally, RSV is a common viral pathogen that causes 64 million acute respiratory infections annually. Our objective was to determine the incidence of hospitalization, healthcare resource use and associated costs of adults hospitalized with RSV in Ontario, Canada.

METHODS

To describe the epidemiology of adults hospitalized with RSV, we used a validated algorithm applied to a population-based healthcare utilization administrative dataset in Ontario, Canada. We created a retrospective cohort of incident hospitalized adults with RSV between September 2010 and August 2017 and followed each person for up to two years. To determine the burden of illness associated with hospitalization and post-discharge healthcare encounters each RSV-admitted patient was matched to two unexposed controls based on demographics and risk factors. Patient demographics were described and mean attributable 6-month and 2-year healthcare costs (2019 Canadian dollars) were estimated.

RESULTS

There were 7,091 adults with RSV-associated hospitalizations between 2010 and 2019 with a mean age of 74.6 years; 60.4 % were female. RSV-coded hospitalization rates increased from 1.4 to 14.6 per 100,000 adults between 2010-2011 and 2018-2019. The mean difference in healthcare costs between RSV-admitted patients and matched controls was $28,260 (95 % CI: $27,728 - $28,793) in the first 6 months and $43,721 over 2 years (95 % CI: $40,383 - $47,059) post-hospitalization.

CONCLUSIONS

RSV hospitalizations among adults increased in Ontario between 2010/11 to 2018/19 RSV seasons. RSV hospitalizations in adults were associated with increased attributable short-term and long-term healthcare costs compared to matched controls. Interventions that could prevent RSV in adults may reduce healthcare burden.

Understanding Policy Decisions and Their Implications Regarding Preventive Interventions for Respiratory Syncytial Virus (RSV) Infection in Canadian Infants: A Primer for Nurses

Respiratory syncytial virus (RSV) is a leading cause of morbidity and hospitalization in young children, and prevention is the primary management strategy. At present, palivizumab, a monoclonal antibody providing immediate passive immunity, rather than a vaccine that induces active immunity, is the only preventive intervention used in routine practice internationally. In Canada, access varies across the country. Prophylaxis policies are mainly driven by cost-effectiveness analyses, and it is crucial that the full costs and benefits of any intervention are captured. Positive results from a new Canadian cost-effectiveness analysis of palivizumab will help address the current inequality in use while providing a framework for future models of RSV preventives. Nurses are the principal educators for parents about the risks of childhood RSV and optimal prevention via basic hygiene, behavioral and environmental measures, and seasonal prophylaxis. Nurses should be provided not only with regular, up-to-date, and accurate information on RSV and the clinical aspects of emerging interventions but be informed on the decision-making governing the use of preventive strategies.

Leveraging Influenza Virus Surveillance From 2012 to 2015 to Characterize the Burden of Respiratory Syncytial Virus Disease in Canadian Adults ≥50 Years of Age Hospitalized With Acute Respiratory Illness

Background

Respiratory syncytial virus (RSV) disease in older adults is undercharacterized. To help inform future immunization policies, this study aimed to describe the disease burden in Canadian adults aged ≥50 years hospitalized with RSV.

Methods

Using administrative data and nasopharyngeal swabs collected from active surveillance among adults aged ≥50 years hospitalized with an acute respiratory illness (ARI) during the 2012-2013, 2013-2014, and 2014-2015 influenza seasons, RSV was identified using a respiratory virus multiplex polymerase chain reaction test to describe the associated disease burden, incidence, and healthcare costs.

Results

Of 7797 patients tested, 371 (4.8%) were RSV positive (2.2% RSV-A and 2.6% RSV-B). RSV prevalence varied by season from 4.2% to 6.2%. Respiratory virus coinfection was observed in 11.6% (43/371) of RSV cases, with influenza A being the most common. RSV hospitalization rates varied between seasons and increased with age, from 8-12 per 100 000 population in adults aged 50-59 years to 174-487 per 100 000 in adults aged ≥80 years. The median age of RSV cases was 74.9 years, 63.7% were female, and 98.1% of cases had ≥1 comorbidity. Among RSV cases, the mean length of hospital stay was 10.6 days, 13.7% were admitted to the intensive care unit, 6.4% required mechanical ventilation, and 6.1% died. The mean cost per RSV case was $13 602 (Canadian dollars) but varied by age and Canadian province.

Conclusions

This study adds to the growing literature on adult RSV burden by showing considerable morbidity, mortality, and healthcare costs in hospitalized adults aged ≥50 years with ARIs such as influenza.

Urgent air transfers for acute respiratory infections among children from Northern Canada, 2005–2014

Background

The incidence of hospitalizations for acute respiratory infections (ARI) among young Indigenous children from Northern Canada is consistently high. ARIs requiring urgent air transfer can be life-threatening and costly. We aimed to describe their epidemiology, estimate age-specific incidences, and explore factors associated with level of care required.

Methods

We undertook a retrospective cohort study of children <5 years old from Northern Canada transferred by urgent air transport for ARI from 2005 through 2014 to 5 pediatric tertiary care centers in Vancouver, Edmonton, Winnipeg, Ottawa and Montreal. Admissions were identified via ARI-related ICD-9/10 coding and forward sortation area. Descriptive statistics and univariable analyses were performed.

Results

Among 650 urgent air transfers, the majority were from Nunavut (n = 349, 53.7%) or Nunavik (n = 166, 25.5%), <6 months old (n = 372, 57.2%), and without underlying comorbidity (n = 458; 70.5%). Estimated annual tertiary care ARI admission rates in infants <1 year old from Nunavut (40.7/1000) and Nunavik (44.5/1000) were tenfold higher than in children aged 1 to 4 years. Bronchiolitis (n = 333, 51.2%) and pneumonia (n = 208, 32.0%) were the most common primary discharge diagnoses. Nearly half required critical care (n = 316, 48.6%); mechanical ventilation rates ranged from 7.2% to 55.9% across centres. The most common primary pathogen was respiratory syncytial virus (n = 196, 30.1%). Influenza A or B was identified in 35 cases (5.4%) and vaccine-preventable bacterial infections in 27 (4.1%) cases.

Interpretation

Urgent air transfers for ARI from Northern Canada are associated with high acuity. Variations in levels of care were seen across referral centers, age groups and pathogens.

Effectiveness and cost-effectiveness of RSV infant and maternal immunization programs: A case study of Nunavik, Canada

BACKGROUND

Despite passive immunization with palivizumab to select high-risk children under two years of age, the health and economic burden of respiratory syncytial virus (RSV) remains substantial. We evaluated the effectiveness and cost-effectiveness of immunization programs with new generations of RSV prophylactics, including long-acting monoclonal antibodies (LAMA) and maternal vaccines, in terms of reducing hospitalizations in Nunavik, a Canadian Arctic region.

METHODS

We developed an agent-based model of RSV transmission and parameterized it with the demographics and burden of RSV in Nunavik, Québec. We compared various immunization strategies, taking into account the costs associated with program delivery and calculating the incremental cost-effectiveness ratio (ICER) using quality-adjusted life-years (QALYs) gained as a measure of effectiveness. Scenario analyses included immunization with palivizumab and LAMA for infants under one year of age, and maternal vaccination in mild, moderate, and severe RSV seasons. Data were analysed from November 1, 2019 to May 1, 2021.

FINDINGS

We found that a Nunavik pilot program with palivizumab which included healthy full-term infants aged 0-2 months in addition to those considered high-risk for complicated RSV disease is not cost-effective, compared to offering palivizumab only to preterm/chronically ill infants under 1 year of age. Using LAMA as prophylaxis produces ICER values of CAD $39,414/QALY (95% Credible Interval [CrI]: $39,314-$40,017) in a mild season (moderately cost-effective) and CAD $5,255/QALY (95% CrI: $5,222-$5,307) in a moderate season (highly cost-effective). LAMA was a dominant (cost-saving with negative incremental costs and positive incremental effects) strategy in a severe RSV season. Maternal vaccination combined with immunization of preterm/chronically ill infants 3-11 months was also a dominant (cost-saving) strategy in all seasons.

INTERPRETATION

The switch from palivizumab in RSV immunization programs to new prophylactics would lead to significant savings, with LAMA being an effective strategy without compromising benefits in terms of reducing hospitalizations.

Burden of illness in infants and young children hospitalized for respiratory syncytial virus: A rapid review

Respiratory syncytial virus (RSV) infections are common among young children and represent a significant burden to patients, their families and the Canadian health system. Here we conduct a rapid review of the burden of RSV illness in children 24 months of age or younger. Four databases (Medline, Embase, Cochrane Database of Clinical Trials, ClinicalTrials.gov from 2014 to 2018), grey literature and reference lists were reviewed for studies on the following: children with or without a risk factor, without prophylaxis and with lab-confirmed RSV infection. Of 29 studies identified, 10 provided within-study comparisons and few examined clinical conditions besides prematurity. For infants of 33-36 weeks gestation (wGA) versus term infants, there was low-to-moderate certainty evidence for an increase in RSV-hospitalizations (n=599,535 infants; RR 2.05 [95% CI 1.89-2.22]; 1.3 more per 100 [1.1-1.5 more]) and hospital length of stay (n=7,597 infants; mean difference 1.00 day [95% CI 0.88-1.12]). There was low-to-moderate certainty evidence of little-to-no difference for infants born at 29-32 versus 33-36 wGA for hospitalization (n=12,812 infants; RR 1.20 [95% CI 0.92-1.56]). There was low certainty evidence of increased mechanical ventilation for hospitalized infants born at 29-32 versus 33-35 wGA (n=212 infants; RR 1.58, 95% CI 0.94-2.65). Among infants born at 32-35 wGA, hospitalization for RSV in infancy may be associated with increased wheeze and asthma-medication use across six-year follow-up (RR range 1.3-1.7). Children with versus without Down syndrome may have increased hospital length of stay (n=7,206 children; mean difference 3.00 days, 95% CI 1.95-4.05; low certainty). Evidence for other within-study comparisons was of very low certainty. In summary, prematurity is associated with greater risk for RSV-hospitalization and longer hospital length of stay, and Down syndrome may be associated with longer hospital stay for RSV. Respiratory syncytial virus-hospitalization in infancy may be associated with greater wheeze and asthma-medication use in early childhood. Lack of a comparison group was a major limitation for many studies.

Overview of the respiratory syncytial virus vaccine candidate pipeline in Canada

A vaccine for respiratory syncytial virus (RSV) has been actively sought for over 60 years due to the health impacts of RSV disease in infants, but currently the only available preventive measure in Canada and elsewhere is limited to passive immunization for high-risk infants and children with a monoclonal antibody. RSV vaccine development has faced many challenges, including vaccine-induced enhancement of RSV disease in infants. Several key developments in the last decade in the fields of cellular immunology and protein structure have led to new products entering late-stage clinical development. As of July 2019, RSV vaccine development is being pursued by 16 organizations in 121 clinical trials. Five technologies dominate the field of RSV vaccine development, four active immunizing agents (live-attenuated, particle-based, subunit-based and vector-based vaccines) and one new passive immunizing agent (monoclonal antibody). Phase 3 clinical trials of vaccine candidates for pregnant women, infants, children and older adults are under way. The next decade will see a dramatic transformation of the RSV prevention landscape.