This statement was prepared and approved by NACI. Recommendations on the use of live, attenuated influenza vaccine (FluMist®): Supplemental Statement on Seasonal Influenza Vaccine for 2011-2012 An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI)†

Live-attenuated vaccine sCPD9 elicits superior mucosal and systemic immunity to SARS-CoV-2 variants in hamsters

Vaccines play a critical role in combating the COVID-19 pandemic. Future control of the pandemic requires improved vaccines with high efficacy against newly emerging SARS-CoV-2 variants and the ability to reduce virus transmission. Here we compare immune responses and preclinical efficacy of the mRNA vaccine BNT162b2, the adenovirus-vectored spike vaccine Ad2-spike and the live-attenuated virus vaccine candidate sCPD9 in Syrian hamsters, using both homogeneous and heterologous vaccination regimens. Comparative vaccine efficacy was assessed by employing readouts from virus titrations to single-cell RNA sequencing. Our results show that sCPD9 vaccination elicited the most robust immunity, including rapid viral clearance, reduced tissue damage, fast differentiation of pre-plasmablasts, strong systemic and mucosal humoral responses, and rapid recall of memory T cells from lung tissue after challenge with heterologous SARS-CoV-2. Overall, our results demonstrate that live-attenuated vaccines offer advantages over currently available COVID-19 vaccines.

Demonstrating the capacity of the National Advisory Committee on Immunization for timely responses to post-market vaccine monitoring signals: Canada's experience with the live-attenuated influenza vaccine

Over the last several years, the recommended use of the live-attenuated influenza vaccine (LAIV) for children has evolved in the United States (US) in response to evidence of a potential decrease in LAIV effectiveness based on post-market monitoring. These issues were not observed in Canada or elsewhere; consequently, recommendations from Canada's National Advisory Committee on Immunization (NACI) and the US Advisory Committee on Immunization Practices (ACIP) on whether to use LAIV differed for two influenza seasons (2016-2017 and 2017-2018). This retrospective describes how NACI arrived at its recommendations in response to post-market signals of reduced LAIV performance from the US in 2013-2014 and again in 2015-2016. NACI's experience with LAIV marks the first time in Canada where a preferential recommendation on the use of an influenza vaccine in a routine immunization program was reversed. This experience highlights the importance of ongoing post-market monitoring of vaccines, international collaboration and careful consideration of local context to inform vaccine recommendations. NACI's capacity for timely responses to post-market vaccine performance signals will facilitate responsiveness to similar post-market monitoring signals from the coronavirus disease 2019 (COVID-19) vaccines.

Influenza vaccination and the evolution of evidence-based recommendations for older adults: A Canadian perspective

Older adults are at high risk from influenza and its complications, and are therefore an important population for prevention efforts. In Canada, public health efforts targeting influenza are multi-pronged and include vaccination programs as well as surveillance which informs the national surveillance reporting platform FluWatch run by the Public Health Agency of Canada. Recommendations regarding use of vaccines are made nationally by the National Advisory Committee on Immunization (NACI) and by the Comité sur l'immunisation du Québec in Quebec, while vaccination programs are planned and delivered at the provincial/territorial level as opposed to as a harmonized national immunization program. NACI performs rigorous targeted literature reviews to inform their statements, and recommendations also vary by whether they apply on Individual (pertaining to decisions for individual patients) vs. Programmatic (informing policy decisions for implementation of publicly funded vaccination programs) levels. This unique context results in inter-provincial variation in vaccine schedules and funded vaccine products. In this paper, the importance of influenza vaccination for older adults is discussed; to provide insights from the Canadian context, the evolution of NACI evidence reviews and recommendations on influenza vaccination is presented.

Summary of the NACI systematic review and recommendation on the use of live attenuated influenza vaccine (LAIV) in HIV-infected individuals

Background

Annual influenza vaccination is recommended for all individuals six months of age and older, including those with HIV infection. Prior to this statement, the National Advisory Committee on Immunization (NACI) stated that live attenuated influenza vaccine (LAIV) was contraindicated for all individuals with HIV infection. The objective of this article is to update NACI's guidance on the use of LAIV for HIV-infected individuals.

Methods

A systematic literature review of the use of LAIV in individuals with HIV was undertaken. The Canadian Adverse Events Following Immunization Surveillance System was searched for reports of adverse events following vaccination with LAIV in HIV-infected individuals. NACI approved the revised recommendations.

Results

NACI concluded that LAIV is immunogenic in children with HIV, and available data suggest that it is safe, although data were insufficient to detect possible uncommon adverse effects. LAIV may be considered as an option for vaccination of children 2-17 years old who meet the following criteria: 1) receiving highly active antiretroviral therapy for at least four months; 2) CD4 count of 500/µL or greater if age 2-5 years, or of 200/µL or greater if age 6-17 years; and 3) HIV plasma RNA less than 10,000 copies/mL. LAIV remains contraindicated for adults with HIV because of insufficient data. Intramuscular influenza vaccination is considered the standard for children living with HIV by NACI and the Canadian Paediatric & Perinatal HIV/AIDS Research Group, particularly for those without HIV viral load suppression (i.e. plasma HIV RNA is 40 copies/mL or greater). However, if intramuscular (IM) vaccination is not accepted by the patient or substitute decision-maker, LAIV would be reasonable for children meeting the criteria listed above.

Conclusion

LAIV may be considered as an option for annual vaccination of selected children with HIV.

Oil-in-water emulsion adjuvants for pediatric influenza vaccines: a systematic review and meta-analysis

Standard inactivated influenza vaccines are poorly immunogenic in immunologically naive healthy young children, who are particularly vulnerable to complications from influenza. For them, there is an unmet need for better influenza vaccines. Oil-in-water emulsion-adjuvanted influenza vaccines are promising candidates, but clinical trials yielded inconsistent results. Here, we meta-analyze randomized controlled trials with efficacy data (3 trials, n = 15,310) and immunogenicity data (17 trials, n = 9062). Compared with non-adjuvanted counterparts, adjuvanted influenza vaccines provide a significantly better protection (weighted estimate for risk ratio of RT-PCR-confirmed influenza: 0.26) and are significantly more immunogenic (weighted estimates for seroprotection rate ratio: 4.6 to 7.9) in healthy immunologically naive young children. Nevertheless, in immunologically non-naive children, adjuvanted and non-adjuvanted vaccines provide similar protection and are similarly immunogenic. These results indicate that oil-in-water emulsion adjuvant improves the efficacy of inactivated influenza vaccines in healthy young children at the first-time seasonal influenza vaccination.

Here, the authors meta-analyze clinical trials comparing adjuvanted and non-adjuvanted influenza vaccines in children and find that oil-in-water emulsion adjuvant improves the efficacy of inactivated influenza vaccines in healthy immunologically naive children.

Cost-effectiveness analysis of the direct and indirect impact of intranasal live attenuated influenza vaccination strategies in children: alternative country profiles

BACKGROUND

Influenza poses a significant burden on healthcare systems and society, with under-recognition in the paediatric population. Existing vaccination policies (largely) target the elderly and other risk groups where complications may arise.

OBJECTIVE

The goal of this study was to evaluate the cost-effectiveness of annual paediatric vaccination (in 2-17-year-olds) with live attenuated influenza vaccination (LAIV), as well as the protective effect on the wider population in England and Wales (base). The study aimed to demonstrate broad applications of the model in countries where epidemiological and transmission data is limited and that have sophisticated vaccination policies (Brazil, Spain, and Taiwan).

METHODS

The direct and indirect impact of LAIV in the paediatric cohort was simulated using an age-stratified dynamic transmission model over a 5-year time horizon of daily cycles and applying discounting of 3.5% in the base case. Pre-existing immunity structure was based on a 1-year model run. Sensitivity analyses were conducted.

RESULTS

In the base case for England and Wales, the annual paediatric strategy with LAIV was associated with improvements in influenza-related events and quality-adjusted life years (QALYs) lost, yielding an incremental cost per QALY of £6,208. The model was robust to change in the key input parameters. The probabilistic analysis demonstrated LAIV to be cost effective in more than 99% of iterations, assuming a willingness-to-pay threshold of £30,000. Incremental costs per QALY for Brazil were £2,817, and for the cases of Spain and Taiwan the proposed strategy was dominant over the current practice.

CONCLUSION

In addition to existing policies, annual paediatric vaccination using LAIV provides a cost-effective strategy that offers direct and indirect protection in the wider community. Paediatric vaccination strategies using LAIV demonstrated clinical and economic benefits over alternative (current vaccination) strategies in England and Wales as well as Brazil, Spain, and Taiwan.

Vaccinating high-risk children with the intranasal live-attenuated influenza vaccine: the Quebec experience

Given the burden of illness associated with influenza, vaccination is recommended for individuals at high risk of complications. The live-attenuated influenza vaccine (LAIV) is administered by intranasal spray, thus directly stimulating mucosal immunity. In this review, we aimed to provide evidence for its efficacy and safety in different paediatric populations. We also share the Quebec experience of LAIV use through a publicly funded vaccination program for children with chronic, high-risk conditions.

RESULTS

from randomized controlled trials in healthy children and in asthmatics have demonstrated superior efficacy of LAIV over the injectable vaccine (IIV). LAIV is well tolerated: its administration is associated with runny nose and nasal congestion, but not with asthma exacerbations and is well tolerated in children with cystic fibrosis, when compared to IIV. The vaccine is well accepted by children and parents and can easily be part of vaccination clinics in paediatric tertiary care centres targeting children with chronic, high-risk conditions, not leading to immunosuppression.

Vaccine recommendations for children and youth for the 2014/2015 influenza season

The Canadian Paediatric Society continues to encourage annual influenza vaccination for ALL children and youth ≥6 months of age. Recommendations from the National Advisory Committee on Immunization for the 2014/2015 influenza season include some important changes: Influenza vaccination is recommended for ALL individuals ≥6 months of age, with particular focus on those at high risk of influenza-related complications and their close contacts. Definitions of high-risk conditions and close contacts have not changed from those of 2013/2014.The preference for intranasal, live attenuated influenza vaccine (LAIV) over trivalent inactivated influenza vaccines for healthy children is restricted to individuals two to six years of age. There is insufficient evidence to recommend LAIV over trivalent inactivated influenza vaccines in older children or in children with chronic health conditions; either vaccine may be used unless there are specific contraindications.Quadrivalent influenza vaccines are expected to be available for the 2014/2015 season and may be used interchangeably with trivalent vaccines. They may offer improved protection.Trivalent or quadrivalent inactivated vaccines may be used in individuals with egg allergy; LAIV has not yet been evaluated in this population and is not recommended at this time.