SEATTLE — There is something different about this year's flu vaccine, and it has the pandemic to thank for it.
For the first time in more than a decade, the shot will target three influenza strains, instead of four. Doctors told KING 5 it is actually a good thing.
It wasn't that long ago when people were collectively asked to mask up and stay indoors to squash the coronavirus. It turns out, those precautions squashed something else along the way.
"The Yamagata strain -- it was already on the decline, and this was just a nail in the coffin for it," said Dr. Matt Gentry, a Washington-based pharmacist for Rite Aid.
He's referring to an influenza strain that has disappeared in recent years.
The U.S. Food and Drug Administration announced in March of this year, the flu vaccine for the 2024-2025 season will be trivalent, which goes after three strains of influenza -- rather than the traditional four strains.
"I was like, you know the flu vaccine is different this year. But not a lot of people know why," Gentry said.
Gentry said the change is exciting.
"The important thing is why it's only three strains this year," Gentry added.
Years of COVID-19 precautions during the pandemic helped prevent the spread of the coronavirus and a particular strain of the flu known as influenza B/Yamagata, which happened to already be on the decline at the time and hasn't been detected since March 2020.
"We eliminated a strain of flu from circulation in the world," Gentry said.
The Centers for Disease Control and Prevention and the World Health Organization said because of the Yamagata strain's absence, it will not be targeted in the flu vaccine this season.
Since the 2012-2013 season, flu shots available were quadrivalent, which targeted four strains: two influenza "A" strains, and two influenza "B" strains.
The CDC said the flu vaccine for the 2024-2025 season will now only target two "A" strains and one "B" strain of the Victoria lineage. The aforementioned B/Yamagata strain is now omitted.
KING 5 talked with Dr. Helen Chu, an infectious diseases professor at UW Medicine's Division of Allergy and Infectious Diseases for further insight.
"Since influenza B is a virus that can only be transmitted person-to-person and doesn't involve pigs or birds, then what happened was that because humans weren't transmitting it to each other, it became completely eliminated," Chu said.
"I think what it tells us is that you can certainly stop transmission of viruses through measures such as masking and staying home while sick. Whether or not we want that level of measures to be taken on a regular basis is probably something to be discussed. But certainly when you have a pandemic and you take those measures, then you can stop transmission of other viruses," Chu said.
While the change in this year's flu shot may seem small to the general public, Gentry said it's huge success.
"All of that pain we went through, it meant something. It mattered," Gentry said.
The CDC can't for sure say the B/Yamagata flu strain is extinct forever. Other B strains of the flu have also disappeared then reemerged. Because of this, the CDC and the WHO will continue to monitor it.
But what about the common cold? The respiratory infections ails countless people during peak season, as well as year-round.
Researchers are better understanding why a person keeps catching a new cold, whereas a person might catch the flu or COVID only once per season.
UW Medicine researchers found it's because there are many different variants of rhinovirus circulating at a given time, which is why a person can catch colds more than once, according to research by Dr. Stephanie Goya, a postdoctoral scientist in laboratory medicine and pathology at UW Medicine.
Goya's research is published in the Journal of Infectious Diseases.
Rhinovirus is the most common virus that causes a cold.
"Each of these versions doesn't mutate, doesn't change very much. So this is very promising to consider the possibility of a vaccine, if we had the chance to know them all," Goya said.
For more information on where to get a COVID or flu vaccine, visit here.