Further Evidence for Bias in Observational Studies of Influenza Vaccine Effectiveness: The 2009 Influenza A(H1N1) Pandemic

Influenza vaccination is annually recommended for specific populations at risk, such as older adults. We estimated the 2018/2019 influenza vaccine effectiveness (IVE) overall, by influenza subtype, type of vaccine, and by time elapsed since vaccination among subjects 65 years old or over in a multicenter prospective study in the Valencia Hospital Surveillance Network for the Study of Influenza and other Respiratory Viruses (VAHNSI, Spain). Information about potential confounders was obtained from clinical registries and/or by interviewing patients and vaccination details were only ascertained by registries. A test-negative design was performed in order to estimate IVE. As a result, IVE was estimated at 46% (95% confidence interval (CI): (16%, 66%)), 41% (95% CI: (−34%, 74%)), and 45% (95% CI: (7%, 67%)) against overall influenza, A(H1N1)pdm09 and A(H3N2), respectively. An intra-seasonal not relevant waning effect was detected. The IVE for the adjuvanted vaccine in ≥75 years old was 45% (2%, 69%) and for the non-adjuvanted vaccine in 65–74 years old was 59% (−16%, 86%). Thus, our data revealed moderate vaccine effectiveness against influenza A(H3N2) and not significant against A(H1N1)pdm09. Significant protection was conferred by the adjuvanted vaccine to patients ≥75 years old. Moreover, an intra-seasonal not relevant waning effect was detected, and a not significant IVE decreasing trend was observed over time.

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Influenza vaccine effectiveness against laboratory-confirmed influenza in hospitalised adults aged 60 years or older, Valencia Region, Spain, 2017/18 influenza season

Eurosurveillance ◽

10.2807/1560-7917.es.2019.24.31.1800461 ◽

2019 ◽

Vol 24 (31) ◽

Author(s):

Ainara Mira-Iglesias ◽

F Xavier López-Labrador ◽

Víctor Baselga-Moreno ◽

Miguel Tortajada-Girbés ◽

Juan Mollar-Maseres ◽

...

Keyword(s):

Influenza Vaccine ◽

Influenza A ◽

Vaccine Effectiveness ◽

Influenza Viruses ◽

Influenza B ◽

Current Season ◽

Hospitalised Patients ◽

Influenza A H1n1 ◽

Vaccine Type ◽

The Impact

Introduction Influenza immunisation is recommended for elderly people each season. The influenza vaccine effectiveness (IVE) varies annually due to influenza viruses evolving and the vaccine composition. Aim To estimate, in inpatients ≥ 60 years old, the 2017/18 trivalent IVE, overall, by vaccine type and by strain. The impact of vaccination in any of the two previous seasons (2016/17 and 2015/16) on current (2017/18) IVE was also explored. Methods This was a multicentre prospective observational study within the Valencia Hospital Surveillance Network for the Study of Influenza and Respiratory Viruses Disease (VAHNSI, Spain). The test-negative design was applied taking laboratory-confirmed influenza as outcome and vaccination status as main exposure. Information about potential confounders was obtained from clinical registries and/or by interviewing patients; vaccine information was only ascertained by registries. Results Overall, 2017/18 IVE was 9.9% (95% CI: −15.5 to 29.6%), and specifically, 48.3% (95% CI: 13.5% to 69.1%), −29.9% (95% CI: −79.1% to 5.8%) and 25.7% (95% CI: −8.8% to 49.3%) against A(H1N1)pdm09, A(H3N2) and B/Yamagata lineage, respectively. For the adjuvanted and non-adjuvanted vaccines, overall IVE was 10.0% (95% CI: −24.4% to 34.9%) and 7.8% (95% CI: −23.1% to 31.0%) respectively. Prior vaccination significantly protected against influenza B/Yamagata lineage (IVE: 50.2%; 95% CI: 2.3% to 74.6%) in patients not vaccinated in the current season. For those repeatedly vaccinated against influenza A(H1N1)pdm09, IVE was 46.4% (95% CI: 6.8% to 69.2%). Conclusion Our data revealed low vaccine effectiveness against influenza in hospitalised patients ≥60 years old in 2017/18. Prior vaccination protected against influenza A(H1N1)pdm09 and B/Yamagata-lineage.

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Age-specific vaccine effectiveness of seasonal 2010/2011 and pandemic influenza A(H1N1) 2009 vaccines in preventing influenza in the United Kingdom

Epidemiology and Infection ◽

10.1017/s0950268812001148 ◽

2012 ◽

Vol 141 (3) ◽

pp. 620-630 ◽

Cited By ~ 30

Author(s):

R. G. PEBODY ◽

N. ANDREWS ◽

D. M. FLEMING ◽

J. McMENAMIN ◽

S. COTTRELL ◽

...

Keyword(s):

Influenza Vaccine ◽

Pandemic Influenza ◽

Influenza A ◽

Vaccine Effectiveness ◽

Influenza B ◽

The United Kingdom ◽

Previous Season ◽

Negative Case ◽

Influenza A H1n1 ◽

Control Study

SUMMARYAn analysis was undertaken to measure age-specific vaccine effectiveness (VE) of 2010/11 trivalent seasonal influenza vaccine (TIV) and monovalent 2009 pandemic influenza vaccine (PIV) administered in 2009/2010. The test-negative case-control study design was employed based on patients consulting primary care. Overall TIV effectiveness, adjusted for age and month, against confirmed influenza A(H1N1)pdm 2009 infection was 56% (95% CI 42–66); age-specific adjusted VE was 87% (95% CI 45–97) in <5-year-olds and 84% (95% CI 27–97) in 5- to 14-year-olds. Adjusted VE for PIV was only 28% (95% CI −6 to 51) overall and 72% (95% CI 15–91) in <5-year-olds. For confirmed influenza B infection, TIV effectiveness was 57% (95% CI 42–68) and in 5- to 14-year-olds 75% (95% CI 32–91). TIV provided moderate protection against the main circulating strains in 2010/2011, with higher protection in children. PIV administered during the previous season provided residual protection after 1 year, particularly in the <5 years age group.

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2553. Individual Patient-Level Data Meta-Analysis of Live Attenuated and Inactivated Influenza Vaccine Effectiveness Among US Children, 2013–2014 Through 2015–2016

Open Forum Infectious Diseases ◽

10.1093/ofid/ofy209.161 ◽

2018 ◽

Vol 5 (suppl_1) ◽

pp. S68-S68

Author(s):

Jessie Chung ◽

Brendan Flannery ◽

Rodolfo Begue ◽

Herve Caspard ◽

Laurie Demarcus ◽

...

Keyword(s):

Influenza Vaccine ◽

Influenza A ◽

The United States ◽

Vaccine Effectiveness ◽

Vaccination Status ◽

Influenza B ◽

Rt Pcr ◽

Current Season ◽

Influenza A H1n1 ◽

Vaccine Type

Abstract Background Quadrivalent live attenuated influenza vaccine (LAIV4) was not recommended for use in the United States for the 2016–2017 and 2017–2018 influenza seasons based on US observational studies of vaccine effectiveness (VE) from 2013–2014 to 2015–2016. We pooled individual patient data on children aged 2–17 years enrolled in 5 US studies during these 3 influenza seasons to further investigate VE by vaccine type. Methods Analyses included 17,173 children enrolled in the US Department of Defense Global Laboratory-based Influenza Surveillance Program, US Influenza Vaccine Effectiveness Network, Influenza Incidence Surveillance Project, Influenza Clinical Investigation for Children, and a Louisiana State University study. Participants’ specimens were tested for influenza by reverse transcription-polymerase chain reaction (RT-PCR), culture, or a combination of rapid antigen testing and RT-PCR. VE was calculated by comparing odds of vaccination with either inactivated influenza vaccine (IIV) or LAIV4 among influenza-positive cases to test-negative controls and calculated as 100 × (1 − odds ratio) in logistic regression models with age, calendar time, influenza season, and study site (random effect). Patients were stratified by prior season vaccination status in a subanalysis. Results Overall, 38% of patients (N = 6,558) were vaccinated in the current season, of whom 30% (N = 1,979) received LAIV4. Pooled VE of IIV against any influenza virus was 51% (95% CI: 47, 54) versus 26% (95% CI: 15, 36) for LAIV4. Point estimates for pooled VE against any influenza by age group ranged from 45% to 58% for IIV and 19% to 34% for LAIV4 during the 3 seasons (Figures 1 and 2). Pooled VE against influenza A(H1N1)pdm09 was 67% (95% CI: 62, 72) for IIV versus 20% (95% CI: −6, 39) for LAIV4. Pooled VE against influenza A(H3N2) was 29% (95% CI: 14, 42) for IIV versus 7% (95% CI: −11, 23) for LAIV4, and VE against influenza B was 52% (95% CI: 42, 60) for IIV and 66% (95% CI: 47, 77) for LAIV4. VE against influenza A(H1N1)pdm09 was lower for LAIV4 versus IIV across all strata of prior season vaccination (Figure 3). Conclusion Consistent with individual studies, our pooled analyses found that LAIV4 effectiveness was reduced for all age groups against influenza A(H1N1)pdm09 compared with IIV. This result did not vary based on prior vaccination status. Disclosures H. Caspard, AstraZeneca: Employee, Salary.

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Vaccine effectiveness against influenza-associated hospitalizations among adults, 2018-2019, US Hospitalized Adult Influenza Vaccine Effectiveness Network

The Journal of Infectious Diseases ◽

10.1093/infdis/jiaa772 ◽

2020 ◽

Author(s):

J M Ferdinands ◽

M Gaglani ◽

S Ghamande ◽

E T Martin ◽

D Middleton ◽

...

Keyword(s):

Influenza Vaccine ◽

Influenza A ◽

Influenza Season ◽

Respiratory Illness ◽

Vaccine Effectiveness ◽

H3n2 Virus ◽

Influenza A H1n1 ◽

The Us ◽

Middle Aged Adults ◽

Residual Confounding

Abstract We estimated vaccine effectiveness for prevention of influenza-associated hospitalizations among adults during the 2018-2019 influenza season. Adults admitted with acute respiratory illness to 14 hospitals of the US Hospitalized Adult Influenza Vaccine Effectiveness Network and testing positive for influenza were cases; patients testing negative were controls. Vaccine effectiveness was estimated using logistic regression and inverse probability of treatment weighting. We analyzed data from 2863 patients with mean age of 63 years. Adjusted VE against influenza A(H1N1)pdm09-associated hospitalization was 51% (95%CI 25, 68). Adjusted VE against influenza A(H3N2) virus-associated hospitalization was −2% (95%CI −65, 37) and differed significantly by age, with VE of −130% (95% CI −374, −27) among adults 18 to ≤56 years of age. Although vaccination halved the risk of influenza-A(H1N1)pdm09-associated hospitalizations, it conferred no protection against influenza A(H3N2)-associated hospitalizations. We observed negative VE for young-and middle-aged adults but cannot exclude residual confounding as a potential explanation.

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Faculty Opinions recommendation of 2012/13 influenza vaccine effectiveness against hospitalised influenza A(H1N1)pdm09, A(H3N2) and B: estimates from a European network of hospitals.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.725317956.793503270 ◽

2015 ◽

Author(s):

Raymond Lin

Keyword(s):

Influenza Vaccine ◽

Influenza A ◽

Vaccine Effectiveness ◽

European Network ◽

Influenza A H1n1

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Influenza Vaccine Effectiveness Against 2009 Pandemic Influenza A(H1N1) Virus Differed by Vaccine Type During 2013–2014 in the United States

The Journal of Infectious Diseases ◽

10.1093/infdis/jiv577 ◽

2016 ◽

Vol 213 (10) ◽

pp. 1546-1556 ◽

Cited By ~ 113

Author(s):

Manjusha Gaglani ◽

Jessica Pruszynski ◽

Kempapura Murthy ◽

Lydia Clipper ◽

Anne Robertson ◽

...

Keyword(s):

United States ◽

Influenza Vaccine ◽

Pandemic Influenza ◽

Influenza A ◽

H1n1 Virus ◽

The United States ◽

Vaccine Effectiveness ◽

Influenza A H1n1 ◽

Vaccine Type

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Influenza vaccine effectiveness against influenza A in children based on the results of various rapid influenza tests in the 2018/19 season

PLoS ONE ◽

10.1371/journal.pone.0249005 ◽

2021 ◽

Vol 16 (3) ◽

pp. e0249005

Author(s):

Masayoshi Shinjoh ◽

Norio Sugaya ◽

Yoshio Yamaguchi ◽

Ichiro Ookawara ◽

Yuji Nakata ◽

...

Keyword(s):

Confidence Interval ◽

Influenza Vaccine ◽

Diagnostic Tests ◽

Influenza A ◽

Control Design ◽

Case Control ◽

Vaccine Effectiveness ◽

Test Results ◽

Negative Case ◽

Influenza A H1n1

During influenza epidemics, Japanese clinicians routinely conduct rapid influenza diagnostic tests (RIDTs) in patients with influenza-like illness, and patients with positive test results are treated with anti-influenza drugs within 48 h after the onset of illness. We assessed the vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children (6 months–15 years old, N = 4243), using a test-negative case-control design based on the results of RIDTs in the 2018/19 season. The VE against influenza A(H1N1)pdm and A(H3N2) was analyzed separately using an RIDT kit specifically for detecting A(H1N1)pdm09. The adjusted VE against combined influenza A (H1N1pdm and H3N2) and against A(H1N1)pdm09 was 39% (95% confidence interval [CI], 30%–46%) and 74% (95% CI, 39%–89%), respectively. By contrast, the VE against non-A(H1N1)pdm09 influenza A (presumed to be H3N2) was very low at 7%. The adjusted VE for preventing hospitalization was 56% (95% CI, 16%–77%) against influenza A. The VE against A(H1N1)pdm09 was consistently high in our studies. By contrast, the VE against A(H3N2) was low not only in adults but also in children in the 2018/19 season.

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2012/13 influenza vaccine effectiveness against hospitalised influenza A(H1N1)pdm09, A(H3N2) and B: estimates from a European network of hospitals

Eurosurveillance ◽

10.2807/1560-7917.es2015.20.2.21011 ◽

2015 ◽

Vol 20 (2) ◽

Cited By ~ 22

Author(s):

M Rondy ◽

O Launay ◽

J Puig-Barberà ◽

G Gefenaite ◽

J Castilla ◽

...

Keyword(s):

Influenza Vaccine ◽

Influenza A ◽

Vaccine Effectiveness ◽

European Network ◽

Binary File ◽

Influenza A H1n1

Binary file ES_Abstracts_Final_ECDC.txt matches

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Interim 2019/20 influenza vaccine effectiveness: six European studies, September 2019 to January 2020

Eurosurveillance ◽

10.2807/1560-7917.es.2020.25.10.2000153 ◽

2020 ◽

Vol 25 (10) ◽

Cited By ~ 3

Author(s):

Angela Rose ◽

Esther Kissling ◽

Hanne-Dorthe Emborg ◽

Amparo Larrauri ◽

Jim McMenamin ◽

...

Keyword(s):

Primary Care ◽

Influenza Vaccine ◽

Influenza A ◽

Age Groups ◽

Vaccine Effectiveness ◽

Influenza B ◽

European Studies ◽

Case Definitions ◽

Point Estimates ◽

Influenza A H1n1

Background Influenza A(H1N1)pdm09, A(H3N2) and B viruses were co-circulating in Europe between September 2019 and January 2020. Aim To provide interim 2019/20 influenza vaccine effectiveness (VE) estimates from six European studies, covering 10 countries and both primary care and hospital settings. Methods All studies used the test-negative design, although there were some differences in other study characteristics, e.g. patient selection, data sources, case definitions and included age groups. Overall and influenza (sub)type-specific VE was estimated for each study using logistic regression adjusted for potential confounders. Results There were 31,537 patients recruited across the six studies, of which 5,300 (17%) were cases with 5,310 infections. Most of these (4,466; 84%) were influenza A. The VE point estimates for all ages were 29% to 61% against any influenza in the primary care setting and 35% to 60% in hospitalised older adults (aged 65 years and over). The VE point estimates against A(H1N1)pdm09 (all ages, both settings) was 48% to 75%, and against A(H3N2) ranged from −58% to 57% (primary care) and −16% to 60% (hospital). Against influenza B, VE for all ages was 62% to 83% (primary care only). Conclusions Influenza vaccination is of continued benefit during the ongoing 2019/20 influenza season. Robust end-of-season VE estimates and genetic virus characterisation results may help understand the variability in influenza (sub)type-specific results across studies.

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