What was the 2020-2021 flu season like?
Flu activity was unusually low throughout the 2020-2021 flu season both in the United States and globally, despite high levels of testing. During September 28, 2020–May 22, 2021 in the United States, 1,675 (0.2%) of 818,939 respiratory specimens tested by U.S. clinical laboratories were positive for an influenza virus. The low level of flu activity during this past season contributed to dramatically fewer flu illnesses, hospitalizations, and deaths compared with previous flu seasons. For comparison, during the last three seasons before the pandemic, the proportion of respiratory specimens testing positive for influenza peaked between 26.2% and 30.3%. In terms of hospitalizations, the cumulative rate of laboratory-confirmed influenza-associated hospitalizations in the 2020-2021 season was the lowest recorded since this type of data collection began in 2005. For pediatric deaths, CDC received one report of a pediatric flu death in a child during the 2020–2021 flu season. Since flu deaths in children became nationally notifiable in 2004, reported flu deaths in children had previously ranged from a low of 37 (during 2011-2012) to a high of 199 (during 2019-2020).
What are possible explanations for the unusually low flu activity?
COVID-19 mitigation measures such as wearing face masks, staying home, hand washing, school closures, reduced travel, increased ventilation of indoor spaces, and physical distancing, likely contributed to the decline in 2020-2021 flu incidence, hospitalizations and deaths. Influenza vaccination may also contributed to reduced flu illness during the 2020–2021 season. Flu vaccine effectiveness estimates for 2020-2021 are not available, but a
record number of influenza vaccine doses (193.8 million doses) were distributed in the U.S. during 2020-2021.