Influenza Vaccine Effectiveness Against All-Cause Mortality Following Laboratory-Confirmed Influenza in Older Adults, 2010-2011 to 2015-2016 Seasons in Ontario, Canada

Systematic review of influenza vaccine effectiveness against laboratory-confirmed influenza among older adults living in aged care facilities

We estimated the effectiveness of influenza vaccines in preventing laboratory-confirmed influenza among older adults in aged care. Electronic database searches were conducted using search terms, and studies were selected as per the selection criteria. Fourteen studies were included for final review. The studies exhibited considerable variation in reported vaccine effectiveness (VE) across different seasons. Among the observational studies, VE ranged from 7.2% to 89.8% against laboratory-confirmed influenza across different vaccines. Randomized clinical trials demonstrated a 17% reduction in infection rates with the adjuvanted trivalent vaccine. The limitations include the small number of included studies conducted in different countries or regions, varied seasons, variations in diagnostic testing methods, a focus on the A/H3N2 strain, and few studies available on the effectiveness of enhanced influenza vaccines in aged care settings. Despite challenges associated with achieving optimal protection, the studies showed the benefits of influenza vaccination in the elderly residents.

Digital Immunization Tracking in Long-Term Care and Assisted Living Facilities

A disproportionate share of the health impacts of COVID-19 has been borne by older adults, particularly those in long-term care facilities (LTCs). Vaccination has been critical to efforts to combat this issue, but as we begin to emerge from this pandemic, questions remain about how to protect the health of residents of LTC and assisted living facilities proactively in order to prevent such a disaster from occurring again. Vaccination, not just against COVID-19, but also against other vaccine-preventable illness, will be a key component of this effort. However, there are currently substantial gaps in the uptake of vaccines recommended for older adults. Technology offers an opportunity to assist in filling these vaccination gaps. Our experiences in Fredericton, New Brunswick suggest that a digital immunization solution would facilitate better uptake of adult vaccines for older adults in assisted and independent living facilities and would help policy and decision makers to identify coverage gaps and develop interventions to protect these individuals.

Long-term COVID-19 booster effectiveness by infection history and clinical vulnerability and immune imprinting: a retrospective population-based cohort study

BACKGROUND

Long-term effectiveness of COVID-19 mRNA boosters in populations with different previous infection histories and clinical vulnerability profiles is inadequately understood. We aimed to investigate the effectiveness of a booster (third dose) vaccination against SARS-CoV-2 infection and against severe, critical, or fatal COVID-19, relative to that of primary-series (two-dose) vaccination over a follow-up duration of 1 year.

METHODS

This observational, matched, retrospective, cohort study was done on the population of Qatar in people with different immune histories and different clinical vulnerability to infection. The source of data are Qatar's national databases for COVID-19 laboratory testing, vaccination, hospitalisation, and death. Associations were estimated using inverse-probability-weighted Cox proportional-hazards regression models. The primary outcome of the study is the effectiveness of COVID-19 mRNA boosters against infection and against severe COVID-19.

FINDINGS

Data were obtained for 2 228 686 people who had received at least two vaccine doses starting from Jan 5, 2021, of whom 658 947 (29·6%) went on to receive a third dose before data cutoff on Oct 12, 2022. There were 20 528 incident infections in the three-dose cohort and 30 771 infections in the two-dose cohort. Booster effectiveness relative to primary series was 26·2% (95% CI 23·6-28·6) against infection and 75·1% (40·2-89·6) against severe, critical, or fatal COVID-19, during 1-year follow-up after the booster. Among people clinically vulnerable to severe COVID-19, effectiveness was 34·2% (27·0-40·6) against infection and 76·6% (34·5-91·7) against severe, critical, or fatal COVID-19. Effectiveness against infection was highest at 61·4% (60·2-62·6) in the first month after the booster but waned thereafter and was modest at only 15·5% (8·3-22·2) by the sixth month. In the seventh month and thereafter, coincident with BA.4/BA.5 and BA.2·75* subvariant incidence, effectiveness was progressively negative albeit with wide CIs. Similar patterns of protection were observed irrespective of previous infection status, clinical vulnerability, or type of vaccine (BNT162b2 vs mRNA-1273).

INTERPRETATION

Protection against omicron infection waned after the booster, and eventually suggested a possibility for negative immune imprinting. However, boosters substantially reduced infection and severe COVID-19, particularly among individuals who were clinically vulnerable, affirming the public health value of booster vaccination.

FUNDING

The Biomedical Research Program and the Biostatistics, Epidemiology, and the Biomathematics Research Core (both at Weill Cornell Medicine-Qatar), Ministry of Public Health, Hamad Medical Corporation, Sidra Medicine, Qatar Genome Programme, and Qatar University Biomedical Research Center.

Effectiveness of vaccination on influenza-related critical illnesses in the elderly population

OBJECTIVES

The prevention of serious influenza-related severe conditions due to influenza is important, particularly in elderly patients, age is a risk factor for death resulting from influenza-related respiratory diseases. The aim of the present study was to investigate the association of influenza vaccination with severe condition requiring critical care and death in elderly people, using vaccine records and healthcare administrative claims data in a Japanese city.

RESULTS

Among 5608 patients aged ≥65 years diagnosed with influenza, we identified 96 patients who had received invasive mechanical ventilation or died. Thereafter, we matched 384 controls with the cases. The cases were less vaccinated than the controls (37.5% vs. 56.0%, P < 0.01). In the multivariate analysis, influenza vaccination was associated with a lower proportion of the composite outcome (odds ratio, 0.35; 95% confidence interval, 0.21-0.60). In patients aged ≥80 years old and those with cardiovascular disease, influenza vaccination was associated with low composite outcomes.

CONCLUSIONS

Influenza vaccination was associated with reduced proportions of receiving invasive mechanical ventilation or influenza-related mortality, particularly in those aged ≥80 years old.

Predictors of all-cause mortality among patients hospitalized with influenza, respiratory syncytial virus, or SARS-CoV-2

BACKGROUND

Shared and divergent predictors of clinical severity across respiratory viruses may support clinical and community responses in the context of a novel respiratory pathogen.

METHODS

We conducted a retrospective cohort study to identify predictors of 30-day all-cause mortality following hospitalization with influenza (N = 45,749; 2010-09 to 2019-05), respiratory syncytial virus (RSV; N = 24 345; 2010-09 to 2019-04), or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; N = 8988; 2020-03 to 2020-12; pre-vaccine) using population-based health administrative data from Ontario, Canada. Multivariable modified Poisson regression was used to assess associations between potential predictors and mortality. We compared the direction, magnitude, and confidence intervals of risk ratios to identify shared and divergent predictors of mortality.

RESULTS

A total of 3186 (7.0%), 697 (2.9%), and 1880 (20.9%) patients died within 30 days of hospital admission with influenza, RSV, and SARS-CoV-2, respectively. Shared predictors of increased mortality included older age, male sex, residence in a long-term care home, and chronic kidney disease. Positive associations between age and mortality were largest for patients with SARS-CoV-2. Few comorbidities were associated with mortality among patients with SARS-CoV-2 as compared with those with influenza or RSV.

CONCLUSIONS

Our findings may help identify patients at greatest risk of illness secondary to a respiratory virus, anticipate hospital resource needs, and prioritize local prevention and therapeutic strategies to communities with higher prevalence of risk factors.

Antigenic drift and epidemiological severity of seasonal influenza in Canada

Seasonal influenza epidemics circulate globally every year with varying levels of severity. One of the major drivers of this seasonal variation is thought to be the antigenic drift of influenza viruses, resulting from the accumulation of mutations in viral surface proteins. In this study, we aimed to investigate the association between the genetic drift of seasonal influenza viruses (A/H1N1, A/H3N2 and B) and the epidemiological severity of seasonal epidemics within a Canadian context. We obtained hemagglutinin protein sequences collected in Canada between the 2006/2007 and 2019/2020 flu seasons from GISAID and calculated Hamming distances in a sequence-based approach to estimating inter-seasonal antigenic differences. We also gathered epidemiological data on cases, hospitalizations and deaths from national surveillance systems and other official sources, as well as vaccine effectiveness estimates to address potential effect modification. These aggregate measures of disease severity were integrated into a single seasonal severity index. We performed linear regressions of our severity index with respect to the inter-seasonal antigenic distances, controlling for vaccine effectiveness. We did not find any evidence of a statistical relationship between antigenic distance and seasonal influenza severity in Canada. Future studies may need to account for additional factors, such as co-circulation of other respiratory pathogens, population imprinting, cohort effects and environmental parameters, which may drive seasonal influenza severity.

A Cohort Study on Influenza Vaccine and All-Cause Mortality in Older Adults: Methodological Concerns and Public Health Implications

Introduction

In 2020, the restrictions adopted to control the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic led to an unprecedented reduction in influenza-related burden. As such, the reduced chance to characterize the circulating virus strains might have increased the risk of vaccine mismatch for the forthcoming winter seasons. The role of an effective influenza vaccination campaign might therefore assume even more value, especially for frail and multimorbid older individuals. Methodological concerns on confounding by indication are always debated in vaccine effectiveness studies and it might be instrumental to give a pragmatic message on an individual’s responsibility to receive the influenza vaccine. We therefore investigated the role of specific confounders to explain the association between influenza vaccine and mortality among older adults.

Methods

Using a primary care database, we formed a cohort of patients aged 65 years or older who were actively registered with their general practitioner (GP) at the beginning of each of nine influenza seasons through to the 2018/2019 season. The study index date was the related seasons’ starting date. Exposure to the influenza vaccine was operationally defined in the 2 months preceding the index date up to 2 weeks before the exit date. Cox regression models were estimated to calculate hazard ratios (HRs) and their 95% confidence intervals (CI) of death between vaccinated and unvaccinated patients in a time-dependent fashion. The potential confounders sequentially entered the model based on their increasing effect size observed in univariate analyses.

Results

Over the 10 years under study, the influenza vaccine showed a significant protective effect in terms of mortality, reaching 13% reduction (HR 0.87, 95% CI 0.80–0.95) in the 2018/2019 influenza season. When we estimated the multivariate model by sequentially adding the potential confounders, there was an inversion of HR (below the unit) that was significantly explained by the covariates coding for a prior history of lower respiratory tract infections and the presence of the pneumococcal vaccine.

Conclusion

In the current pandemic scenario, we cannot divert attention to proper use of face masks, social distancing, and hand hygiene, which are important measures to prevent influenza and other respiratory viral infections. Nonetheless, their effectiveness might be negligible without acceptable coverage for influenza vaccine, especially in older patients with a history of lower respiratory tract infections, which appears to be the main source of confounding by indication.

Aerosolisation in endonasal endoscopic pituitary surgery

PURPOSE

To determine the particle size, concentration, airborne duration and spread during endoscopic endonasal pituitary surgery in actual patients in a theatre setting.

METHODS

This observational study recruited a convenience sample of three patients. Procedures were performed in a positive pressure operating room. Particle image velocimetry and spectrometry with air sampling were used for aerosol detection.

RESULTS

Intubation and extubation generated small particles (< 5 µm) in mean concentrations 12 times greater than background noise (p < 0.001). The mean particle concentrations during endonasal access were 4.5 times greater than background (p = 0.01). Particles were typically large (> 75 µm), remained airborne for up to 10 s and travelled up to 1.1 m. Use of a microdebrider generated mean aerosol concentrations 18 times above baseline (p = 0.005). High-speed drilling did not produce aerosols greater than baseline. Pituitary tumour resection generated mean aerosol concentrations less than background (p = 0.18). Surgical drape removal generated small and large particles in mean concentrations 6.4 times greater than background (p < 0.001).

CONCLUSION

Intubation and extubation generate large amounts of small particles that remain suspended in air for long durations and disperse through theatre. Endonasal access and pituitary tumour resection generate smaller concentrations of larger particles which are airborne for shorter periods and travel shorter distances.