The latest Public Health Alerts report details influenza activity, vaccination rates, and flu-related deaths last season in Massachusetts, noting a record level of influenza-like illness (ILI) and influenza deaths in the 2024-25 season and 10 reported flu-related deaths in children.

Public Health Alerts, a new collaboration between NEJM Evidence and CIDRAP, fills a gap in reliable data, offering expert-reviewed reports that translate frontline observations into actionable public health evidence. An NEJM Evidence editorial  explains the initiative further.

441 deaths overall, 10 in children

The percentage of visits for ILI reported by sentinel sites in Massachusetts peaked at almost 12% in early February 2025 and remained above the epidemic threshold until mid-April. This was the highest rate of ILI in Massachusetts as far back as data are accessible, which was the 2001-02 season.

Among adults 20 to 64 years old, emergency department (ED) visits for flu peaked at 66.8 per 100,000 population. Adults 65 to 79 years had a rate of 1.6 times that, while those 80 and older had a rate 3.0 times higher.

Flu vaccination rates for the 2024-25 season were lower than most previous seasons, at 40.4% by mid-April 2025.

Massachusetts has recorded deaths associated with influenza every year, with total deaths across all age-groups ranging from 18 during the 2020-21 season to 441 during the 2024-25 season. The 10 pediatric deaths were the most since before the 2009 H1N1 flu pandemic.

Seven 7 of the deaths occurred in children with preexisting conditions, and eight of 10 had not received that year’s flu vaccine.