Flu shot protects against some severe COVID-19 effects, study claims

Flu shot protects against some severe COVID-19 effects, study claims

New research suggests that patients who received their annual flu vaccine before contracting coronavirus may have some degree of protection against severe effects associated with COVID-19, such as stroke, sepsis and deep vein thrombosis (DVT). 

Data collected from patients around the world and presented at the European Congress of Clinical Microbiology & Infectious Disease (ECCMID) suggests that those who had received a flu vaccine prior to COVID-19 were both less likely to visit the emergency department and less likely to be admitted to the intensive care unit (ICU). 

Researchers from University of Miami Miller School of Medicine created two groups of 37,377 patients that had certain risk factors for severe COVID-19 effects such as age, obesity, pulmonary disease, smoking and other health issues. The first group had received the flu vaccine between two weeks and six months prior to contracting COVID-19, while members of the second group had also contracted COVID-19 but did not receive a prior flu shot. 


The team then compared the incidence rate of 15 adverse outcomes including stroke, sepsis and DVT as mentioned above, as well as pulmonary embolism, acute respiratory failure, acute respiratory distress syndrome, joint pain, renal failure, anorexia, heart attack, pneumonia, emergency department visits, hospital admissions, ICU admission and death within 120 days of testing positive between the two groups. 

Among the COVID-19 group who did not receive a flu vaccine, researchers noted a 20% increased likelihood of being admitted to ICU, a 45% increased likelihood of developing sepsis, a 58% increased likelihood of having a stroke and a 58% increased likelihood of visiting the emergency room. 

The researchers noted the risk of death was not reduced. 


It is not known exactly how the shot provides protection against COVID-19, and the team said their findings bolster the call for more research. 

“Influenza vaccination may even benefit individuals hesitant to receive a COVID-19 vaccine due to the newness of technology,” Susan Taghioff, a research assistant with the University of Miami Miller School of Medicine said. “Despite this, the influenza vaccine is by no means a replacement for the COVID-19 vaccine, and we advocate for everyone to receive their COVID-19 vaccine if able to. Continued promotion of the influenza vaccine also has the potential to help the global population avoid a possible ‘twindemic’ – a simultaneous outbreak of both influenza and coronavirus.” 

Taghioff said regardless of the degree of protection afforded by the shot, “simply being able to conserve global health care resources by keeping the number of influenza cases under control is reason enough to champion continued efforts to promote influenza vaccination.” 


Several ongoing studies or planned research is examining a combination vaccine that would target flu, COVID-19 and other respiratory illnesses at the same time. Moderna, which is currently testing an mRNA flu vaccine in clinical trial participants, is among the companies who have announced future plans to create a combination vaccine.