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 introduced new guidelines concerning the influenza vaccine. The directive states: “Effective immediately, the annual influenza vaccine is voluntary for all Active and Reserve Component Service members and Department of War civilian personnel.”
The origin of this policy shift, whether from Secretary Hegseth or the White House, remains uncertain. Regardless, it overlooks the severe impact the flu had on the military in 1918 and contradicts 249 years of U.S. military policy aimed at safeguarding the fighting capability of American forces.
Politics Prevail
The administration’s skepticism towards vaccines is well-documented. Shortly after President Trump returned to the Oval Office, he enacted Executive Order 14184. This order allowed military personnel discharged for refusing the COVID-19 vaccine to be reinstated with their rank and pay restored, along with corrections to their military records. RFK Jr. has actively worked to diminish confidence in vaccines. In the event of another influenza pandemic, mRNA technology is the only known method to rapidly produce an effective vaccine. However, in August 2025, the HHS terminated nearly $500 million in contracts for mRNA vaccine development.
The “Spanish Flu” (1918-1919)
The 1918-1919 flu pandemic ranks among the most lethal in history. Initially reported in Spain, it became known as the “Spanish Flu.” This name arose because the warring nations of the U.S., U.K., France, and Germany suppressed reports to maintain morale, while neutral Spain did not, leading to the misconception that the outbreak began there.
The deadly strain likely originated in Haskell County, Kansas, in January 1918, with the first recorded cases appearing at Camp Funston (now Fort Riley), Kansas, in March. It swiftly spread across crowded barracks and troop trains in the U.S. and reached France, Great Britain, and Germany by April 1918. Over two years, nearly a third of the global population was infected, resulting in 50-100 million deaths.
Without a vaccine or antibiotics to combat complications, control measures included isolating victims, quarantining contacts, occasional mask-wearing, using disinfectants, and limiting public gatherings, all inconsistently applied.
Unlike typical flu outbreaks that affect the very young and old, the 1918-1919 flu targeted young adults. By the end of 2018, influenza had killed nearly as many U.S. soldiers—around 45,000—as those who died in combat (53,402). The high death toll among young adults in the U.S. led to a 12-year drop in life expectancy.
Health Protection Preserves Fighting Strength
Historically, the U.S. military has prioritized health protection. In 1777, General George Washington mandated smallpox inoculations for the Continental Army, reasoning that unchecked smallpox posed a greater threat than the enemy’s sword.
Union Major Jonathan Letterman, known as the “Father of Battlefield Medicine,” emphasized that medical officers were established not just to treat the sick but to maintain the army’s health, thereby enhancing its effectiveness in combat and endurance.
Health protection is crucial, as the U.S. military tracks disease and non-battle injury rates to assess leadership and medical support. When health protection fails, the consequences can be severe. Shortly after reports of flu-like illnesses in Wuhan, the USS Theodore Roosevelt deployed from San Diego, and during a visit to Danang, Vietnam, the crew was exposed to COVID-19. Despite precautions, over 1,200 sailors were infected, one died, and the ship was forced to dock in Guam for two months, all before the first mRNA COVID-19 vaccine was available.
Unit Cohesion Is Essential
Modern warfare relies heavily on unit cohesion, with teams depending on one another to complete missions. If multiple members fall ill, the unit’s effectiveness is compromised. The USS Theodore Roosevelt is an extreme example, but there are others.
Vaccinations against flu and other diseases protect not only individual soldiers but also the health of their units. General Washington recognized this importance, which appears to be overlooked by Secretary Hegseth. Allowing servicemembers to opt out of a simple, safe, and effective flu shot could lead others to question their dedication to the team and mission.
A Possible Way Out
Hegseth’s memo permits the Services and their component commands to request exceptions to this policy within the next 15 days. However, following the recent dismissal of Army Chief of Staff Randy George, few might be willing. If many do request exceptions, it could send a strong message to Pentagon leadership and potentially prompt the Secretary of War to reconsider his decision.
