Due to the COVID-19 pandemic, this year’s flu shot is seeing its first major change in over a decade. Since 2013, flu shots have included four viral strains. But global travel restrictions reduced spread and may have eliminated one of them. As travel resumes, influenza vaccines remain crucial for controlling spread and preventing illness.
Influenza shots provide the most effective prevention against severe forms of the flu. According to the CDC, everyone six months of age and older should receive the flu vaccine each year. Annual vaccination is a critical to protect vulnerable groups and limit spread.
How Did the COVID-19 Pandemic Affect Flu Strains?
COVID-19 measures, including travel bans and social distancing, helped suppress global flu circulation. These steps reduced the spread of the B/Yamagata flu strain, which disappeared in March 2023. As a result, researchers removed B/Yamagata from this year’s U.S. flu vaccines.
Flu vaccines in the U.S. get updates each year to target strains expected to circulate. From 1978 to 2013, flu vaccines protected against three strains. In 2013, they shifted to a four-strain (quadrivalent) formula. Now, the vaccine returns to a trivalent version.
Doctors will recommend specific vaccines based on age and health needs. The switch to a trivalent vaccine does not change how doctors administer the flu shot.
It’s possible that B/Yamagata still exists in areas with limited flu surveillance. Its disappearance reflects collaboration between countries, including the U.S., China, and Russia. Global flu burden has not decreased despite the stain’s absence.
With fewer virus strains to focus on, vaccine producers may increase manufacturing capacity. A larger vaccine supply could prevent millions of infections, hundreds of thousands of deaths, and billions of dollars lost in healthcare costs and productivity.
This change to a three-strain vaccine also benefits workers involved in vaccine production. Removing the B/Yamagata strain reduces accidental exposures to live viruses during manufacturing. By focusing on fewer strains, the vaccine production process becomes safer.
How Could Lifted COVID-19 Travel Bans Affect Global Flu Transmission?
As global travel resumes, once isolated flu strains may begin circulating again. During the pandemic, reduced exposure to the flu lowered natural immunity levels. These tendencies will increase future flu severity and transmission.
The two remaining A strains and one B strain of influenza now show less genetic diversity. Due to the COVID-19 pandemic, each strain prevailed in specific regions. A strains dominate South and Southeast Asia and West Africa, and the B strain has a strong foothold in China.
Isolated flu pockets may develop unique mutations. The effectiveness of current vaccines diminishes as mutated strains begin circulating.
People born in the 2020s may be more vulnerable to seasonal influenza due to a lack of natural exposure. Compounding the issue, the remaining B strain, B/Victoria, may begin to evolve faster. B/Yamagata offered some cross-protection against B/Victoria. Its absence may speed up B/Victoria’s development and spread.
Researchers are exploring new ways to prevent the flu, including universal flu vaccines. New technology, like the mRNA platforms used in COVID-19 vaccines, show promise for the flu. This mRNA technology could enable faster production and adaptation to new flu strains.
Conclusion
Even with recent changes, flu vaccination prevents severe illness and protects public health. This year’s flu shot, now trivalent, is a streamlined but effective tool against seasonal flu. Vaccination remains our best defense against the global, viral illness.
Have an upcoming trip? Passport Health offers a wide variety of options to help keep you safe from disease, including flu vaccines. Call or book online to schedule your appointment today.
Logan Hamilton is a health and wellness freelance writer for hire. He’s passionate about crafting crystal-clear, captivating, and credible content that elevates brands and establishes trust. When not writing, Logan can be found hiking, sticking his nose in bizarre books, or playing drums in a local rock band. Find him at loganjameshamilton.com.
