The research, released as a preprint that has not yet been peer-reviewed, indicates that a flu vaccine against the influenza virus may also trigger the body to produce broad infection-fighting molecules that combat the pandemic-causing coronavirus. Workers who received a flu vaccine, the researchers found, were 39 percent less likely to test positive for the coronavirus as of June 1, 2020. These findings do not prove that flu vaccines prevent COVID-19, however. In Netea’s new study, he and his team exposed a subset of immune cells to the BCG vaccine before the flu vaccine. They found that exposure to both vaccines increased cytokine production even more than the flu vaccine alone.