Adjuvanted versus non-adjuvanted standard-dose influenza vaccines in preventing all-cause hospitalizations in the elderly: a cohort study with nested case-control analyses over 18 influenza seasons

Examining the effectiveness and duration of adjuvanted vs. non-adjuvanted influenza vaccines in protecting older adults against symptomatic SARS-CoV-2 infection

Annual influenza vaccination is one of the main public health measures able to drastically reduce the burden of this infectious disease. Some evidence suggests 'trained immunity' triggered by influenza vaccine might reduce the risk of SARS-CoV-2 infection. Adjuvanted influenza vaccines are known to induce a broader cross-reactive immunity. No studies investigated the effect of adjuvanted vs. non-adjuvanted influenza vaccines on the risk of symptomatic SARS-CoV-2 infection. A case-control analysis nested in a cohort of subjects aged ≥65 years and immunized with adjuvanted or non-adjuvanted influenza vaccines was conducted. Although no statistically significant (OR = 0.87; P = .082) difference between the two vaccine types was observed for the 9-month follow-up period, a 17% (OR = 0.83; P = .042) reduction in the odds of COVID-19 was observed for adjuvanted vaccines with a 6-month follow-up. Further evidence is needed, but these results might have implications given the complexity of the upcoming winter seasons, in which the co-occurrence of influenza, SARS-CoV-2 and other respiratory infections (e.g., syncytial virus) might be unpredictable.

Mapping and ranking outcomes for the evaluation of seasonal influenza vaccine efficacy and effectiveness: a delphi study

BACKGROUND

Protection provided by seasonal influenza vaccination (SIV) may be measured against numerous outcomes, and their heterogeneity may hamper decision-making. The aim of this study was to explore outcomes used for estimation of SIV efficacy/effectiveness (VE) and obtain expert consensus on their importance.

RESEARCH DESIGN AND METHODS

An umbrella review was first conducted to collect and map outcomes considered in systematic reviews of SIV VE. A Delphi study was then performed to reach expert convergence on the importance of single outcomes, measured on a 9-point Likert scale, in principal target groups, namely children, working-age adults, older adults, subjects with co-morbidities and pregnant women.

RESULTS

The literature review identified 489 outcomes. Following data reduction, 20 outcomes were selected for the Delphi process. After two Delphi rounds and a final consensus meeting, convergence was reached. All 20 outcomes were judged to be important or critically important. More severe outcomes, such as influenza-related hospital encounters and mortality with or without laboratory confirmation, were generally top-ranked across all target groups (median scores ≥8 out of 9).

CONCLUSIONS

Rather than focusing on laboratory-confirmed infection per se, experimental and observational VE studies should include more severe influenza-related outcomes because they are expected to exercise a greater impact on decision-making.

Time lapses between distribution of influenza vaccines to health authorities and their administration by General Practitioners (GPs) to older adults: a retrospective study over five influenza seasons in Italy

BACKGROUND

Delays in influenza vaccine delivery and administration can hinder vaccine coverage and protection. This study examines the differentials in distributing and administering adjuvanted trivalent (aTIV) and quadrivalent influenza vaccines (aQIV) to older adults in Italy's primary care setting and its potential impact on hospitalization risk over 5 epidemic seasons.

METHODS

Using a primary care database, individuals aged ≥ 65 years were selected. The proportion of vaccine distribution to regional authorities and subsequent administration by GPs was estimated using census data. Using quantile (median) regression, we examined the relationship between velocities of vaccine distribution and administration (doses/week) and the incidence of hospitalizations.

RESULTS

Over the 5 influenza seasons, the velocity of distribution and administration of aTIV/aQIV ranged 341-833 and 152-270 median doses/week; no trend was yielded for the difference between these velocities (p = 0.189) or vaccine coverage (p = 0.142). An association was observed for each differential dose/week between distributed and administered vaccines and all-cause hospitalizations with a 10% increase in 2017-2018, 54% in 2018-2019, and 12% in 2020-2021 season.

CONCLUSIONS

These findings highlight the importance of minimizing the time lapse between vaccine distribution and administration to mitigate the impact of influenza and address factors that contribute to vaccination barriers.

Population-level benefits of increasing influenza vaccination uptake among Italian older adults: results from a granular panel model

Background

The impact of seasonal influenza vaccination (SIV) on mortality is still controversial; some studies have claimed that increasing vaccination coverage rates is beneficial, while others have found no significant association. This study aimed to construct a granular longitudinal dataset of local VCRs and assess their effect on pneumonia- and influenza-related (P&I) mortality among Italian adults aged ≥ 65 years.

Methods

NUTS-3 (nomenclature of territorial units for statistics) level data on SIV coverage were collected via a survey of local data holders. Fixed- and random-effects panel regression modeling, when adjusted for potential confounders, was performed to assess the association between local SIV coverage rates and P&I mortality in older adults.

Results

A total of 1,144 local VCRs from 2003 to 2019 were ascertained. In the fully adjusted fixed-effects model, each 1% increase in vaccination coverage was associated (P < 0.001) with a 0.6% (95% CI: 0.3-0.9%) average over-time decrease in P&I mortality. With an annual average of 9,293 P&I deaths in Italy, this model suggested that 56 deaths could have been avoided each year by increasing SIV coverage by 1%. The random-effects model produced similar results. The base-case results were robust in a sensitivity analysis.

Conclusion

Over the last two decades, Italian jurisdictions with higher SIV uptake had, on average, fewer P&I deaths among older adults. Local policy-makers should implement effective strategies to increase SIV coverage in the Italian senior population.

[Enhanced targeted influenza vaccines - New evidence shows higher effectiveness in older adults]

Seasonal influenza causes a significant burden of disease in the German population and is associated with high societal costs. Persons aged 60 years and older are particularly at risk due to immunosenescence and chronic disease and account for a large proportion of influenza-associated hospitalizations and deaths. Adjuvanted, high-dose, recombinant and cell-based influenza vaccines have been developed to improve the effectiveness compared with conventional vaccines. Recent observational studies show better effectiveness of adjuvanted vaccine over conventional vaccines and similar effectiveness to the high-dose vaccine in older adults. Some countries have already considered the new evidence in their vaccination recommendations for the current or earlier seasons. The availability of the vaccines for older adults should also be ensured in Germany to guarantee a high level of vaccination protection.