Since 2010, an average of 45 million people were infected with the flu annually; with hundreds of thousands of those people hospitalized in the United States. During the COVID-19 pandemic, still widespread across the globe, something strange happened: the 2020-21 flu season was almost completely absent. The CDC reports the lowest number of flu hospitalizations, since it began tracking this data in 2005, and has reported only one pediatric death compared to 196 deaths in 2019-20. The next lowest year for seasonal flu was 2011-2012 and so far, this year’s flu season is approximately 2/3 below that rate.

Influenza has been a part of the rhythm of life in this country and around the world since the 1918 H1N1 (Spanish Flu) outbreak. That outbreak lasted over four cycles between 1918 and 1920 and has been estimated to be responsible for 500 million infections and 20 to 50 million deaths. Through reconstruction of the 1918 H1N1 strain, researchers found its virulence may have been attributed to its ability to replicate in the absence of trypsin and other characteristics not evidenced in subsequent strains.  Identifying these characteristics formed the basis of additional research to better prepare for the threat from the likely emergence of another flu virus and to identify the balance between minimizing damage to lung tissues while treating the viral insult. However, the  tragic consequences of the 1918 flu were likely exacerbated by the conditions of World War I. Conditions that included malnourishment, overcrowded medical camps and hospitals, and poor hygiene were common in spite of a general understanding in the medical community of the of the connection between hygiene and health. Germ theory, a product of the 19th century’s cholera outbreak, provided the context for a fundamental shift in disease prevention and treatment during the 20th century; but even with that shift, seasonal flu persists, as does its continual toll on human life.

COVID-19 is the 21st century threat that has led many in public health and beyond to compare it to 1918 because of its overall impact on the global society. As we top 3 million dead, and as countries around the globe struggle to contain the pandemic by introducing strong social and economic measures along with public health messaging, prevention messages such as frequent handwashing and avoiding hand contact with the face prominent for the flu were applied to COVID-19, unsurprisingly, because both are highly transmissible respiratory infections. With COVID-19, the public was also asked or mandated to maintain physical distance from other people indoors and outdoors, avoid large gatherings, use protective face coverings, and avoid unnecessary travel. The virus and these prevention measures in aggregate caused a near absolute disruption of society and economic life.

COVID-19 also spurred the design, development, and first-in-public use of an unprecedented set of new products designed to better track the outbreak and its consequences and prevent transmission. This includes medical countermeasures like nucleic acid vaccines, rapid testing, pre-symptomatic screening, and improved mask designs, built environment interventions like air filtration and UV-C inactivation, and newly validated public health surveillance capabilities like digital contact tracing, genomic surveillance, wastewater screening, and other early-warning systems. 

Since 1945 we have relied on vaccines as the primary public health intervention to reduce flu burden. However, their efficacy and utilization have been limited. Fewer than 50% of Medicare beneficiaries are vaccinated each year, and efficacy hovers around 37%. While the economic and social disruptions required to combat COVID-19 were painful or unacceptable to many, what if we could more precisely and lightly deploy targeted public health interventions, testing, and medical countermeasures to prevent initial spread of flu without disruption?