WASHINGTON, DC - Secretary of War Pete Hegseth (Photo by Anna Moneymaker/Getty Images)

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On Tuesday, April 20, Secretary of War Pete Hegseth announced new guidance on influenza vaccination. His memo states: “Effective immediately, the annual influenza vaccine is voluntary for all Active and Reserve Component Service members and Department of War civilian personnel.”

Whether this policy change was Sec. Hegseth’s idea or originated in the White House is unclear. Either way, it ignores the devastating impact flu had on our armed forces in 1918 and it contradicts 249 years of U.S. military doctrine regarding the importance of preserving the fighting strength of U.S. forces.

Politics Prevail

The administration’s hostility to vaccines is well known. One week after President Trump returned to the Oval Office, he signed Executive Order 14184. It allowed military servicemembers who had been voluntarily or involuntarily discharged for refusing COVID-19 vaccination to be reinstated with restored rank, back pay, and correction of their military records. RFK Jr. has gone out of his way to undermine trust in vaccines. When (not if) the next pandemic strain of influenza takes hold, mRNA is the only known technology capable of quickly producing an effective vaccine. But in Aug 2025, HHS canceled nearly $500 million in contracts that were funding mRNA vaccine development.

The “Spanish Flu” (1918-1919)

The flu pandemic of 1918-1919 was one of the deadliest in world history. Because the first reports of widespread illness and death originated in Spain, it became known as the “Spanish Flu.” The only reason is the major warring nations (the U.S., U.K., France and Germany) suppressed reports to preserve morale, but Spain, a neutral country, did not. As a result, the public assumed that it originated in Spain.

In fact, the deadly strain probably emerged in Haskell County, Kansas, in January 1918. In March, the first documented cases were identified at Camp Funston (now Fort Riley), Kansas. From there, it quickly spread through crowded barracks and troop trains traveling across the U.S. Cases appeared in France, Great Britain, and Germany in April 1918. Within two years, nearly a third of the global population were infected. 50-100 million died.

With no vaccine to protect against infection and no antibiotics to treat complications, disease control was limited to isolating victims, quarantining close contacts, occasional mask-wearing, use of disinfectants and restricting public gatherings – all of which were applied unevenly.

Most flu outbreaks harm the very young and the very old. The 1918-1919 flu targeted young adults. By the end of 2018, influenza killed nearly as many U.S. soldiers—about 45,000—as the number that died in combat (53,402). In the U.S., so many young adults died that life expectancy dropped by 12 years.

Health Protection Preserves Fighting Strength

Throughout its history, the U.S. military has valued health protection. In 1777, General George Washington ordered the innoculation of the Continental Army against smallpox. In a letter to the director of the Continental Army’s medical department Washington explained his reasoning: “Necessity not only authorizes but seems to require the measure, for should the disorder [smallpox] infect the Army in the natural way, and rage with its usual Virulence, we should have more to dread from it than from the sword of the enemy.”

Union Major Jonathan Letterman, is widely regarded as the “Father of Battlefield Medicine." Shortly after the Civil War, he observed: “A corps of medical officers was not established solely for the purpose of attending the wounded and sick. The leading idea is to strengthen the hands of the Commanding General by keeping his army in the most vigorous health, thus rendering it, in the highest degree, efficient for enduring fatigue and privation, and for fighting.”

Health protection is so important that the U.S. military monitors every unit’s disease and non-battle injury (DNBI) rate to evaluate its leadership and medical support.

When health protection fails, the consequences can be grave. Less than 3 weeks after Chinese officials reported a cluster of flu-like illnesses in Wuhan, the USS Theodore Roosevelt (TR), a nuclear-powered aircraft carrier, deployed from San Diego on Jan. 17, 2020. During a port visit to Danang, Vietnam in March, some of the crew were exposed to COVID-19; all are quarantined. Despite taking every precaution to prevent transmission, the disease ultimately infected more than 1200 sailors, killed one, and forced the ship to dock in Guam for two months while extensive and costly measures were taken to deal with the outbreak. All of this unfolded 6+ months before the first mRNA vaccine against COVID-19 was available.

Unit Cohesion Is Essential

War has become so technologically advanced that crews, units and special ops teams rely on one another to accomplish their mission. If several fall ill, the unit quickly loses its effectiveness. The TR is an extreme example, but there are many others.

Vaccinating against flu and other dangerous diseases not only protects the health of the individual soldier, sailor, airman or Marine; it also protects the health of their unit. GEN George Washington understood this. Apparently, Sec. Hegseth does not. Allowing Servicemembers to opt out of something as simple, safe and effective as a flu shot might also lead other members of the unit to question their commitment to the team and the mission.

A Possible Way Out

Hegseth’s memo allows the Services and their component commands to request exceptions to this policy within the next 15 days. In light of his recent sacking of Army Chief of Staff Randy George, few may be willing. If, however, most do, it will send a powerful message to Pentagon leadership, and hopefully, inspire the SECWAR to rethink his decision.