Influenza epidemiology and influenza vaccine effectiveness during the 2015–2016 season: results from the Global Influenza Hospital Surveillance Network

Abstract

Background The Global Influenza Hospital Surveillance Network is an international platform whose primary objective is to study severe cases of influenza requiring hospitalization. Methods During the 2015–2016 influenza season, 11 sites in the Global Influenza Hospital Surveillance Network in nine countries (Russian Federation, Czech Republic, Turkey, France, China, Spain, Mexico, India, and Brazil) participated in a prospective, active-surveillance, hospital-based epidemiological study. Influenza infection was confirmed by reverse transcription-polymerase chain reaction. Influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza was estimated using a test-negative approach. Results 9882 patients with laboratory results were included of which 2415 (24.4%) were positive for influenza, including 1415 (14.3%) for A(H1N1)pdm09, 235 (2.4%) for A(H3N2), 180 (1.8%) for A not subtyped, 45 (0.5%) for B/Yamagata-lineage, 532 (5.4%) for B/Victoria-lineage, and 33 (0.3%) for B not subtyped. Of included admissions, 39% were < 5 years of age and 67% had no underlying conditions. The odds of being admitted with influenza were higher among pregnant than non-pregnant women (odds ratio, 2.82 [95% confidence interval (CI), 1.90 to 4.19]). Adjusted IVE against influenza-related hospitalization was 16.3% (95% CI, 0.4 to 29.7). Among patients targeted for influenza vaccination, adjusted IVE against hospital admission with influenza was 16.2% (95% CI, − 3.6 to 32.2) overall, 23.0% (95% CI, − 3.3 to 42.6) against A(H1N1)pdm09, and − 25.6% (95% CI, − 86.3 to 15.4) against B/Victoria lineage. Conclusions The 2015–2016 influenza season was dominated by A(H1N1)pdm09 and B/Victoria-lineage. Hospitalization with influenza often occurred in healthy and young individuals, and pregnant women were at increased risk of influenza-related hospitalization. Influenza vaccines provided low to moderate protection against hospitalization with influenza and no protection against the predominant circulating B lineage, highlighting the need for more effective and broader influenza vaccines. Electronic supplementary material The online version of this article (10.1186/s12879-019-4017-0) contains supplementary material, which is available to authorized users.

Predictors for influenza vaccination among Thai pregnant woman: The role of physicians in increasing vaccine uptake

“…[8][9][10][11][12][13][14] A study has shown the influenza vaccine also provided low-to-moderate protection against hospitalization with influenza virus infection. 2 Reductions of 13% of preterm births and 26% of low birth weight were reported, 8,9,15 but no effect on small for gestational age was reported. 16 The safety of influenza vaccination during pregnancy was determined through post-licensure vaccine safety monitoring platforms: pregnancy exposure registries; active and passive surveillance systems; and observational studies.…”

“…Pregnant women are at increased risk of hospitalization due to influenza compared with both the general population and women of childbearing age, although there is inconsistent and limited evidence that influenza virus infection causes adverse pregnancy outcomes . While some studies have reported little or no increased risk of preterm birth among women who were hospitalized with influenza during pregnancy, others found an approximately four‐fold increased risk of preterm birth .…”

“…Influenza vaccination during pregnancy effectively prevents infection among pregnant women and confers protection to their infants during the first few months of life . A study has shown the influenza vaccine also provided low‐to‐moderate protection against hospitalization with influenza virus infection . Reductions of 13% of preterm births and 26% of low birth weight were reported, but no effect on small for gestational age was reported .…”

Clinical Characteristics and Outcomes of Influenza A and B Virus Infection in Adult Australian Hospitalised Patients

“…Pneumonia is a major complication of in uenza that may be associated with mortality, other common complications arise due to exacerbation of chronic medical issues, while cardiac and neurological complications e.g. encephalitis are rare [23,24]. Known risk factors for complications of in uenza include: older age, preexisting cardiopulmonary disease, immunosuppression, obesity, neurological and other common medical conditions [25,26].…”

A comparison of epidemiology and clinical outcomes between influenza A H1N1pdm09 and H3N2 based on multicenter surveillance from 2014 to 2018 in South Korea

“…8 Data in the post-pandemic era generally showed that A(H1N1)pdm09 was associated with younger patients and greater severity compared to A(H3N2). [9][10][11][12][13] However, some inconsistencies exist due to heterogeneous setting of each study such as different participated countries, healthcare resources, vaccination rates, and other potential confounders. Therefore, we pursue to reveal more clear evidence of difference between influenza A subtypes with minimizing confounders in highly vaccinated, well-developed single country, South Korea.…”