Vanderbilt University Medical Center is leading a multicenter national study to evaluate the effectiveness of the influenza vaccine for preventing the flu’s most serious side effects — admission to an intensive care unit (ICU), organ failure and death.
The Influenza Vaccine Effectiveness in the Critically Ill (IVY) study, funded by the Centers for Disease Control and Prevention (CDC), will enroll about 700 adults during the 2019-2020 flu season who are hospitalized with symptoms of severe acute respiratory infection. The patients will include about 500 ICU patients and 200 non-ICU patients, said Wesley Self, MD, MPH, associate professor of Emergency Medicine and the study’s principal investigator.
“Historically, the many studies evaluating the effectiveness of the influenza vaccine have focused on whether the vaccine completely prevented illness. The question has been ‘if people get their flu shot, will it prevent them from getting sick at all?’ Self said. “Now we are studying whether the vaccine prevents patients from becoming critically ill. People may still get sick with a minor illness if they get the flu shot, but does it prevent severe illness? Will the flu shot attenuate the severity of the disease?”
Each year influenza causes about 9.3 million to 49 million illnesses, 140,000 to 960,000 hospitalizations and 12,000 to 79,000 deaths in the United States. Vaccination is the primary strategy to reduce illnesses and deaths from the flu. The U.S. Advisory Committee on Immunization Practices recommends annual flu vaccine for all Americans older than 6 months old who do not have a specific contraindication for the vaccine.
The CDC has preliminarily conducted flu vaccine effectiveness studies to assess how well the vaccine works in preventing ICU admissions. A previous study led by Mark Thompson, PhD, a lead CDC influenza scientist, was conducted over four flu seasons (2012-2015) and found that flu vaccine prevented severe disease. They found the flu vaccine prevented influenza-associated ICU admission.
The VUMC-led IVY study is a follow-up study to Thompson’s CDC study and other work. VUMC is serving as the clinical coordinating center, data coordinating center, single IRB, central laboratory and enrolling site for the study. It was selected to lead the study based on its expertise in influenza epidemiology and conducting critical care clinical research centers. Nine other academic medical centers in the U.S. will also participate.
“Our goal is to quantify how effective the flu vaccine is for preventing people from getting critically ill. We’re specifically investigating whether the vaccine has benefits to patients in terms of preventing organ failure and death,” Self said.
The new information will help inform how strong the recommendations for annual flu vaccination should be and help frame discussions about how and why to make better vaccines,” he added.
Self said it’s largely unknown why some people who were previously healthy become critically ill when they get influenza while others recover rapidly after only a minor illness.
“These cases are relatively rare but are so severe that preventing them is very important,” Self said. “We know some things that put people at risk, such as certain comorbidities and pregnancy. But there’s not a lot known about why some people seemingly just get a very bad cold and some get critically ill. We’re trying to help close that knowledge gap.”
Other VUMC investigators in the IVY study include: H. Keipp Talbot, MD, MPH, associate professor of Medicine; Carlos Grijalva, MD, MPH, associate professor of Health Policy; Natasha Halasa, MD, MPH, associate professor of Pediatrics; Chris Lindsell, PhD, professor of Biostatistics; and Todd Rice, MD, MSCI, associate professor of Medicine.
