ArticleAmerican journal of epidemiology2013
Further evidence for bias in observational studies of influenza vaccine effectiveness: the 2009 influenza A(H1N1) pandemic.
Article in American journal of epidemiology, 2013. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 27 papers, 3 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
27 citing papers in PubMed, 3 syntheses or guidelines pooled it.
- Frequency and impact of confounding by indication and healthy vaccinee bias in observational studies assessing influenza vaccine effectiveness: a systematic review.BMC infectious diseases · 2015Pooled it
- Vaccines for the prevention of seasonal influenza in patients with diabetes: systematic review and meta-analysis.BMC medicine · 2015Pooled it
- Pooled it
- Unmeasured confounding and misclassification in studies estimating vaccine effectiveness against hospitalisation and death using electronic health records (EHRs): an evaluation of a multi-country European retrospective cohort study.BMC medical research methodology · 2025Article
- The Effect of Influenza Vaccination on Hospitalization and Mortality Among People With Dementia.Journal of the American Geriatrics Society · 2025Article
- Confounding and Negative Control Methods in Observational Study of SARS-CoV-2 Vaccine Effectiveness: A Nationwide, Population-Based Danish Health Registry Study.Clinical epidemiology · 2024Article
- The impact of EV71 vaccination program on hand, foot and mouth disease in Zhejiang Province, China: A negative control study.Infectious Disease Modelling · 2023Article
- Covid-19 vaccination programme effectiveness against SARS-CoV-2 related infections, hospital admissions and deaths in the Apulia region of Italy: a one-year retrospective cohort study.Scientific reports · 2022Article
- Effects of Influenza Vaccination in Patients with Interstitial Lung Diseases: An Epidemiological Claims Data Analysis.Annals of the American Thoracic Society · 2022Article
- Identifying and managing adverse drug reactions: Qualitative analysis of patient reports to the UK yellow card scheme.British journal of clinical pharmacology · 2022Article
- Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data.Lancet (London, England) · 2021Observational
- Trends in Influenza Vaccine Uptake and Severe Influenza-Related Outcomes at Kaiser Permanente Southern California, 2007-2017.The Permanente journal · 2021Article
- Infections causing stroke or stroke-like syndromes.Infection · 2020Review
- Comparative Effectiveness of High-Dose Versus Standard-Dose Influenza Vaccine Among Patients Receiving Maintenance Hemodialysis.American journal of kidney diseases : the official journal of the National Kidney Foundation · 2020Article
- Restriction of Pharmacoepidemiologic Cohorts to Initiators of Medications in Unrelated Preventive Drug Classes to Reduce Confounding by Frailty in Older Adults.American journal of epidemiology · 2019Article
- Challenges in estimating influenza vaccine effectiveness.Expert review of vaccines · 2019Review
- Risk Of Urticaria In Geriatric Stroke Patients Who Received Influenza Vaccination: A Retrospective Cohort Study.Clinical interventions in aging · 2019Article
- The importance and implications of comparator selection in pharmacoepidemiologic research.Current epidemiology reports · 2018Article
- Controlling for Frailty in Pharmacoepidemiologic Studies of Older Adults: Validation of an Existing Medicare Claims-based Algorithm.Epidemiology (Cambridge, Mass.) · 2018Article
- Controlling confounding by frailty when estimating influenza vaccine effectiveness using predictors of dependency in activities of daily living.Pharmacoepidemiology and drug safety · 2017Article
Corrections and comments
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Authors and funding
10 authors.
Funding
Abstract
Preinfluenza periods have been used to test for uncontrolled confounding in studies of influenza vaccine effectiveness, but some authors have claimed that confounding differs in preinfluenza and influenza periods. We tested this claim by comparing estimates of the vaccine-mortality association during the 2009/2010 influenza year, when there was essentially no circulation of seasonal influenza in the United States, and 2007/2008, a typical influenza year. We pooled data on seniors (adults aged ≥65 years) from 7 US managed care organizations that participated in the Vaccine Safety Datalink Project. We defined influenza vaccination, all-cause mortality, and potential confounders from administrative databases. We quantified the vaccine-mortality association using Cox regression. During 2007/2008, the adjusted hazard ratio was 0.44 prior to influenza season, 0.62 during influenza season, and 0.71 after influenza season. A similar pattern was observed during 2009/2010, when any effect of seasonal influenza vaccine observed during all time periods must have resulted from confounding: 0.65 during the autumn, 0.80 during the winter, and 0.84 during the summer. In a year with minimal seasonal influenza, we found no evidence that confounding in autumn preinfluenza periods is qualitatively different from confounding in winter. This supports the use of preinfluenza periods as control time periods in studies of influenza vaccine effectiveness.
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.