All those flu shots you gave? Here’s how they helped your patients

“Does it really work?” It’s a common question every year during flu shot season. Now, a new systematic analysis shows all those needles in all those arms are effective in reducing severe illness should an influenza infection occur. The systematic review by Canadian researchers provides more evidence that the seasonal influenza vaccine is effective in reducing hospitalization, pneumonia, ICU admission and death. The researchers examined data from 165 test-negative design studies, where patients hospitalized for respiratory illness are tested for influenza and then compared based on vaccination status. There were more than 670,000 patients included in the studies. Read: Influenza: High-dose vaccine may reduce inflammatory heart disease risk in seniorsInfluenza vaccines were effective in reducing influenza-associated hospitalization by 42%. Vaccination reduced the risk of death by 36% and the risk of pneumonia, ICU admission and need for a ventilator by more than 50% each. The vaccine effectiveness for preventing hospitalization and the need for ICU or ventilation was higher in some seasons than others, depending on how close the vaccine matched the circulating strain.Vaccine effectiveness for preventing hospitalization was highest in children under 17 years old. It was greater against H1N1 subtypes compared to H3N2 subtypes and quadrivalent vaccines had a higher vaccine effectiveness against hospitalization (45%) compared to trivalent formulations (36%). “This was a very, very comprehensive study. Previous work like this has looked at relatively few outcomes, but ours looked at several hard outcomes beyond just hospitalization and did so across a vast body of literature. Doing so revealed a strong bottom line: The seasonal flu shot reduces very severe influenza-related outcomes,” said senior author Dr. Mark Loeb, an infectious disease physician and a professor in McMaster University’s department of pathology and molecular medicine, in a university press release.The researchers were inspired to conduct the meta-analysis after the experience with COVID-19 vaccines, showing immunization reducing hospitalizations even after new variants emerged and breakthrough infections became more common, Matthew S. Miller said. Miller is executive director of Global Nexus and scientific director of the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University.“That experience really changed the global mindset around what we should look for in vaccines—it helped us recognize that keeping people alive and out of the hospital is a critically important property of an effective vaccine.”The researchers wanted to investigate if influenza vaccines also helped reduce severe outcomes of the flu. Their findings support the results of other systematic reviews. The paper was published in Clinical Microbiology and Infection as a journal pre-proof, meaning it has been peer reviewed by may have additional copyediting prior to final publication.

All those flu shots you gave? Here’s how they helped your patients

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