Vaccine effectiveness against laboratory-confirmed influenza in Europe – Results from the DRIVE network during season 2018/19

Stuurman, Anke L.; Bollaerts, Kaatje; Alexandridou, Maria; Biccler, Jorne Lionel; Díez-Domingo, Javier; Nohynek, Hanna; Rizzo, Caterina; Turunen, Topi; Riera-Montes, Margarita

doi:10.1016/j.vaccine.2020.07.063

Cited by 23 publications

(32 citation statements)

References 6 publications

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“…In general, the estimated IVE levels are in line with other studies [ 13 - 17 ]. In particular, all these studies indicate that IVE in elderly people usually does not exceed 50%.…”

Section: Discussionsupporting

confidence: 91%

Spotlight influenza: Estimation of influenza vaccine effectiveness in elderly people with assessment of residual confounding by negative control outcomes, Finland, 2012/13 to 2019/20

2021

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Background Cohort studies on vaccine effectiveness are prone to confounding bias if the distribution of risk factors is unbalanced between vaccinated and unvaccinated study subjects. Aim We aimed to estimate influenza vaccine effectiveness in the elderly population in Finland by controlling for a sufficient set of confounders based on routinely available register data. Methods For each of the eight consecutive influenza seasons from 2012/13 through 2019/20, we conducted a cohort study comparing the hazards of laboratory-confirmed influenza in vaccinated and unvaccinated people aged 65–100 years using individual-level medical and demographic data. Vaccine effectiveness was estimated as 1 minus the hazard ratio adjusted for the confounders age, sex, vaccination history, nights hospitalised in the past and presence of underlying chronic conditions. To assess the adequacy of the selected set of confounders, we estimated hazard ratios of off-season hospitalisation for acute respiratory infection as a negative control outcome. Results Each analysed cohort comprised around 1 million subjects, of whom 37% to 49% were vaccinated. Vaccine effectiveness against laboratory-confirmed influenza ranged from 16% (95% confidence interval (CI): 12–19) to 48% (95% CI: 41–54). More than 80% of the laboratory-confirmed cases were hospitalised. The adjusted off-season hazard ratio estimates varied between 1.00 (95% CI: 0.94–1.05) and 1.08 (95% CI: 1.01–1.15), indicating that residual confounding was absent or negligible. Conclusion Seasonal influenza vaccination reduces the hazard of severe influenza disease in vaccinated elderly people. Data about age, sex, vaccination history and utilisation of hospital care proved sufficient to control confounding.

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“…In general, the estimated IVE levels are in line with other studies [ 13 - 17 ]. In particular, all these studies indicate that IVE in elderly people usually does not exceed 50%.…”

Section: Discussionsupporting

confidence: 91%

Spotlight influenza: Estimation of influenza vaccine effectiveness in elderly people with assessment of residual confounding by negative control outcomes, Finland, 2012/13 to 2019/20

2021

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“…Surveillance data on influenza are gathered systematically through international consortia such as Global Influenza Hospital Surveillance Network (GIHSN) and Development of Robust and Innovative Vaccine Effectiveness (DRIVE) [6,7]. Romania participates in these international networks by collecting yearly prospective data from patients hospitalized for severe acute respiratory infections.…”

Section: Introductionmentioning

confidence: 99%

Clinical and molecular epidemiology of influenza viruses from Romanian patients hospitalized during the 2019/20 season

et al. 2021

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Two main mechanisms contribute to the continuous evolution of influenza viruses: accumulation of mutations in the hemagglutinin and neuraminidase genes (antigenic drift) and genetic re-assortments (antigenic shift). Epidemiological surveillance is important in identifying new genetic variants of influenza viruses with potentially increased pathogenicity and transmissibility. In order to characterize the 2019/20 influenza epidemic in Romania, 1042 respiratory samples were collected from consecutive patients hospitalized with acute respiratory infections in the National Institute for Infectious Diseases “Prof. Dr. Matei Balș”, Bucharest Romania and tested for influenza A virus, influenza B virus and respiratory syncytial virus (RSV) by real-time PCR. Out of them, 516 cases were positive for influenza, with relatively equal distribution of influenza A and B. Two patients had influenza A and B co-infection and 8 patients had influenza-RSV co-infection. The most severe cases, requiring supplemental oxygen administration or intensive care, and the most deaths were reported in patients aged 65 years and over. Subtyping showed the predominance of A(H3N2) compared to A(H1N1)pdm09 pdm09 (60.4% and 39.6% of all subtyped influenza A isolates, respectively), and the circulation of Victoria B lineage only. Influenza B started to circulate first (week 47/2019), with influenza A appearing slightly later (week 50/2019), followed by continued co-circulation of A and B viruses throughout the season. Sixty-eight samples, selected to cover the entire influenza season and all circulating viral types, were analysed by next generation sequencing (NGS). All A(H1N1)pdm09 sequences identified during this season in Romania were clustered in the 6b1.A clade (sub-clades: 6b1.A.183P -5a and 6b1.A.187A). For most A(H1N1)pdm09 sequences, the dominant epitope was Sb (pepitope = 0.25), reducing the vaccine efficacy by approximately 60%. According to phylogenetic analysis, influenza A(H3N2) strains circulating in this season belonged predominantly to clade 3C.3A, with only few sequences in clade 3C.2A1b. These 3C.2A1b sequences, two of which belonged to vaccinated patients, harbored mutations in antigenic sites leading to potential reduction of vaccine efficacy. Phylogenetic analysis of influenza B, lineage Victoria, sequences showed that the circulating strains belonged to clade V1A3. As compared to the other viral types, fewer mutations were observed in B/Victoria strains, with limited impact on vaccine efficiency based on estimations.

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“…For example, SIVE against any laboratory-confirmed influenza and influenza A(H1N1)pdm09 in people of 18–49 years old was found to be 77% and 67%, and in the age group of 65 years and older, 51% and 63%, respectively. In addition, lower SIVE estimates against any influenza and A(H1N1)pdm09 were reported among hospitalized older people as compared with patients aged 18–64 years across Europe [ 18 , 19 , 20 ]. For instance, SIVE against any influenza and influenza A(H1N1)pdm09 reported by the European Development of Robust and Innovative Vaccine Effectiveness (DRIVE) network among patients aged 18–64 were 40% and 51%, and among persons 65 years old and older, 27% and 35%, respectively [ 18 ].…”

Section: Discussionmentioning

confidence: 99%

“…In addition, lower SIVE estimates against any influenza and A(H1N1)pdm09 were reported among hospitalized older people as compared with patients aged 18–64 years across Europe [ 18 , 19 , 20 ]. For instance, SIVE against any influenza and influenza A(H1N1)pdm09 reported by the European Development of Robust and Innovative Vaccine Effectiveness (DRIVE) network among patients aged 18–64 were 40% and 51%, and among persons 65 years old and older, 27% and 35%, respectively [ 18 ]. Similarly, SIVE against any influenza and influenza A(H1N1)pdm09 in Northern Spain among hospitalized older adults was 26% and 47% [ 19 ].…”

Section: Discussionmentioning

confidence: 99%

“…Our SIVE estimates against influenza A(H3N2) are in line with other studies in hospitalized populations. Low SIVE point estimates against influenza A(H3N2) were reported by the DRIVE as 2% among 18–64-year-old patients and 12% among persons 65 years old and older [ 18 ]. Consistent SIVE estimates were found in Denmark against influenza A(H3N2) among hospitalized patients aged 65 years old and older (7%) [ 24 ], as well as in other studies across Europe among hospitalized population [ 19 , 25 , 26 , 27 ].…”

Section: Discussionmentioning

confidence: 99%

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Age-Specific Seasonal Influenza Vaccine Effectiveness against Different Influenza Subtypes in the Hospitalized Population in Lithuania during the 2015–2019 Influenza Seasons

et al. 2021

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Background: Continuous monitoring of seasonal influenza vaccine effectiveness (SIVE) is needed due to the changing nature of influenza viruses and it supports the decision on the annual update of vaccine composition. Age-specific SIVE was evaluated against different influenza subtypes in the hospitalized population in Lithuania during four influenza seasons. Methods: A test-negative case-control study design was used. SIVE and its 95% confidence intervals (95% CI) were calculated as (1 – odds ratio (OR)) × 100%. Results: Adjusted SIVE in 18–64-year-old individuals against influenza A, A(H1N1)pdm09 and B/Yamagata were 78.0% (95% CI: 1.7; 95.1%), 88.6% (95% CI: −47.4; 99.1%), and 76.8% (95% CI: −109.9; 97.4%), respectively. Adjusted SIVE in individuals aged 65 years and older against influenza A, influenza B, and B/Yamagata were 22.6% (95% CI: −36.5; 56.1%), 75.3% (95% CI: 12.2; 93.1%) and 73.1% (95% CI: 3.2; 92.5%), respectively. Unadjusted SIVE against influenza A(H3N2) among 18–64-year-old patients was 44.8% (95% CI: −171.0; 88.8%) and among those aged 65 years and older was 5.0% (95% CI: −74.5; 48.3%). Conclusions: Point estimates suggest high SIVE against influenza A in 18–64-year-old participants, and against influenza B and B/Yamagata in those 65 years old and older.

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Vaccine effectiveness against laboratory-confirmed influenza in Europe – Results from the DRIVE network during season 2018/19

Cited by 23 publications

References 6 publications

Spotlight influenza: Estimation of influenza vaccine effectiveness in elderly people with assessment of residual confounding by negative control outcomes, Finland, 2012/13 to 2019/20

Spotlight influenza: Estimation of influenza vaccine effectiveness in elderly people with assessment of residual confounding by negative control outcomes, Finland, 2012/13 to 2019/20

Clinical and molecular epidemiology of influenza viruses from Romanian patients hospitalized during the 2019/20 season

Age-Specific Seasonal Influenza Vaccine Effectiveness against Different Influenza Subtypes in the Hospitalized Population in Lithuania during the 2015–2019 Influenza Seasons

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