Prevention of Influenza Hospitalization Among Adults in the United States, 2015–2016: Results From the US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN)

Abstract

Background Evidence establishing effectiveness of influenza vaccination for prevention of severe illness is limited. The US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) is a multiyear test-negative case-control study initiated in 2015–2016 to estimate effectiveness of vaccine in preventing influenza hospitalization among adults. Methods Adults aged ≥18 years admitted to 8 US hospitals with acute respiratory illness and testing positive for influenza by polymerase chain reaction were cases; those testing negative were controls. Vaccine effectiveness was estimated with logistic regression adjusting for age, comorbidities, and other confounding factors and stratified by frailty, 2-year vaccination history, and clinical presentation. Results We analyzed data from 236 cases and 1231 controls; mean age was 58 years. More than 90% of patients had ≥1 comorbidity elevating risk of influenza complications. Fifty percent of cases and 70% of controls were vaccinated. Vaccination was 51% (95% confidence interval [CI], 29%–65%) and 53% (95% CI, 11%–76%) effective in preventing hospitalization due to influenza A(H1N1)pdm09 and influenza B virus infection, respectively. Vaccine was protective for all age groups. Conclusions During the 2015–2016 US influenza A(H1N1)pdm09–predominant season, we found that vaccination halved the risk of influenza-association hospitalization among adults, most of whom were at increased risk of serious influenza complications due to comorbidity or age.

Fatores associados à Síndrome Respiratória Aguda Grave em uma Região Central do Brasil

“…This study allowed observing SARI notifications in the state of Goiás for six years. Analyzing the confirmed cases' sociodemographic characteristics, we observed no significant difference regarding gender, unlike studies carried out in New Zealand, the U.S., and France, in which females were predominant [12][13][14][15][16] . Regarding the age group, the largest number of people affected was aged between 20 and 59 years, a group that is not part of the indication for vaccination against Influenza by the Brazilian Ministry of Health.…”

Respiratory and Nonrespiratory Diagnoses Associated With Influenza in Hospitalized Adults

“…We identified acute diagnoses by ICD codes, a method commonly used to classify patient diagnoses in several studies of influenza complications, 8,30 which may have inherent limitations that led to misclassification. 31 For example, there may be differences in how medical that fulfill the criteria for influenza-like illness, with some study findings 32,33 suggesting that only 50% to 79% of adults with influenza will meet the influenza-like illness definition. In situations when a patient does not present with recognizable influenza symptoms, such as influenza-like illness, practitioners may not test for influenza.…”

Vaccine Effectiveness Against Pediatric Influenza Hospitalizations and Emergency Visits

“…25 The test-negative design is widely used nationally and internationally for observational studies of influenza VE, including in previous NVSN and other US VE publications, and among ambulatory and hospitalized adults and children. 8,10,12,13,24,[26][27][28][29][30][31][32][33][34] This methodology is considered to reduce bias associated with confounding by health care-seeking behavior, to lower rates of misclassification of influenza status, and to be better at identifying control patients who arise from the same source population as case patients, which is particularly important for studies of severe influenza outcomes, such as hospitalization. [30][31][32][33][34] VE was calculated as (1 2 the adjusted odds ratio) 3 100%.…”