Flu Vaccine Is Safe for Hospitalized Patients

Kaiser Permanente study supports routine vaccination of patients during hospital stays

Press Release
Female doctor giving hospital patient a flu vaccine.

PASADENA, Calif. — Hospitalized patients who received the flu vaccine had no increased risk of outpatient visits or hospital readmission within seven days of discharge, according to a Kaiser Permanente study published today in Mayo Clinic Proceedings.

The study also showed that vaccinating hospital patients did not increase the risk of fever or rates of laboratory evaluations for infection. It also showed that the vast majority of patients who were not vaccinated during their hospital stay remained unvaccinated for the full flu season.

“We know rates of inpatient flu vaccination are low, often due to physician concerns that the vaccine could complicate healing or delay hospital discharge,” said Sara Y. Tartof, PhD, MPH, study lead author, Kaiser Permanente Southern California Department of Research & Evaluation. “Our findings demonstrate that not vaccinating patients during a hospitalization may be a missed opportunity. Right now, only 28 percent of patients not already vaccinated prior to hospitalization are being vaccinated before they leave the hospital.”

This study builds upon previous research that showed surgical patients who received the flu vaccine during their hospital stay did not have increased risks of complications or delay in discharge compared to surgical patients who were not vaccinated during their stay.

The flu is a highly contagious respiratory infection that can cause serious complications, hospitalizations and, in some cases, even death. Some people — such as older adults, young children and people with certain health conditions — are at high risk for serious complications if they get the flu. In addition to recommending annual flu vaccination for people ages 6 months and older, the Centers for Disease Control and Prevention recommends hospitalized patients who are eligible receive the flu vaccine before discharge.

This retrospective cohort study looked at the electronic health records of more than 250,000 patients ages 6 months and older who were hospitalized in a Kaiser Permanente hospital in Southern California during any of three flu seasons from 2011 to 2014 with admission and discharge dates between September 1 and March 31 of the following calendar year.

Researchers found:

  • 71 percent of patients vaccinated during their hospital stay were vaccinated on the day of discharge.
  • 74 percent of those who miss the opportunity to vaccinate before or during hospitalization remained unvaccinated throughout the season.
  • No increased risk of hospital readmissions, outpatient visits, fever, or clinical evaluations for infection among patients who received the flu vaccine during their hospital stay.

“This research backs up what many physicians have known intuitively for some time: Giving patients the flu vaccine while they are hospitalized is convenient and, most important, safe,” said Bruno J. Lewin, MD, a family practice physician at the Kaiser Permanente Los Angeles Medical Center. “Unless there are contraindications, physicians should have no hesitation to vaccinate patients with the flu vaccine while they are hospitalized.”

The study was funded through the Vaccine Safety Datalink by the Centers for Disease Control and Prevention.

Other authors of the study include senior author Steven J. Jacobsen, MD, PhD; and Lei Qian, PhD; In-Lu Amy Liu, MS; Hung Fu Tseng, PhD; Lina S. Sy, MPH; and Rulin C. Hechter, MD, PhD, of the Kaiser Permanente Southern California Department of Research & Evaluation; and Bruno J. Lewin, MD, with the Southern California Permanente Medical Group.

Vaccine research is an active area of study at Kaiser Permanente.

About the Kaiser Permanente Southern California Department of Research & Evaluation
The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiologic research, health services research, biostatistics research, and behavioral research as well as clinical trials. Major areas of study include chronic disease, infectious disease, cancer, drug safety and effectiveness, and maternal and child health. Headquartered in Pasadena, California, the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general public. Visit kp.org/research.

About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, Kaiser Permanente has a mission to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 12.2 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal Permanente Medical Group physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to kp.org/share.