On Dec. 4, 2020, it was reported in JAMA that high-dose influenza (commonly known as flu) vaccines are no better than regular-dose influenza vaccines in reducing deaths and hospitalizations among patients with underlying heart disease.

The results do not change well-established findings about the value of an annual influenza vaccine for persons with heart disease and other chronic illnesses, and do not change the recommendation for an annual influenza vaccine for most people.

To determine if there is benefit in the higher dose, the NHLBI funded the Influenza Vaccine to Effectively Stop Cardio Thoracic Events and Decompensated heart failure (INVESTED) trial, a randomized, double-blind trial conducted at 157 medical centers in the United States and Canada over three influenza seasons. The trial, which was launched in September 2016, included a total of 5,260 patients who had been recently hospitalized for a cardiovascular event, including heart attack within the previous year or heart failure within the previous two years.

At the end of the study, the composite total of hospitalizations and deaths was roughly equal for both flu vaccine groups. The researchers observed 883 hospitalizations due to cardiovascular or pulmonary causes and 92 deaths from any cause in the high-dose vaccine group, while they saw 846 hospitalizations for these events and 78 deaths from any cause in the regular-dose vaccine group. The difference was not statistically significant.

The study was funded by the National Heart, Lung, and Blood Institute.