Rachel V Thomas

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G155E H1N1 Mutation In US Raises Concerns: Can This Year’s Flu Shot Still Protect You?

Scientists have identified a new <span>H1N1</span> mutation, G155E, in US flu samples, raising questions about immunity and vaccine protection as the <a href="https://www.healthandme.com/health-news/flu-activity-rises-early-in-us-uk-and-japan-why-experts-urge-vaccination-before-winter-article-156307089" data-type="tilCustomLink">flu season</a> begins early.

Early laboratory findings suggest the mutation may make some H1N1 strains harder for existing antibodies to recognize. However, the vaccine’s effectiveness specifically against G155E remains uncertain, and there is no evidence yet that the mutation makes the flu shot ineffective.

<h2>H1N1 Becomes The Dominant Flu Strain In US</h2>

According to the US Centers for Disease Control and Prevention’s (<span>CDC</span>) October 2 report, 53 of 55 influenza A samples undergoing subtyping were H1N1, while two were H3N2. No influenza B viruses were reported in this group.

Researchers at the University of Washington identified G155E in 13 of 17 sequenced H1N1 samples collected from hospitals and clinics in the Seattle area.

<h2>Could G155E Affect Flu Shot Effectiveness?</h2>

<strong>Also read: </strong><a href="https://www.healthandme.com/health-wellness/flu-2026-symptoms-to-watch-for-as-new-season-begins-article-156254381" data-type="tilCustomLink">Flu 2026: Symptoms To Watch For As New Season Begins</a>

The 2026-2027 flu vaccines approved by the US Food and Drug Administration target H1N1, H3N2 and an influenza B virus.

Dr. Jennifer Duchon, a pediatric infectious disease expert at Mount Sinai Children’s Hospital, told Reuters that younger people may have had limited exposure to this year’s H1N1 strain.

“What people are a bit worried about is that the H1N1 strain this year hasn't been seen by a lot of younger folk, so it may be more severe in them,” she said.

However, this concern does not establish that G155E causes more severe disease. Flu vaccine effectiveness varies by season and depends partly on how well vaccine strains match circulating viruses. 

Scott Hensley, a microbiologist at the University of Pennsylvania, told Reuters that two of this season’s three vaccine components appear well matched to circulating strains. He also recommended getting vaccinated early.

The American Medical Association also recommends annual flu vaccination for people aged six months and older, unless they have a medical reason not to receive it.

<h2>G155E: Who Could Be More Vulnerable?</h2>

<strong>Read More</strong>: <a href="https://www.healthandme.com/health-wellness/flu-vaccine-why-october-is-a-good-time-to-get-your-family-vaccinated-article-156324870" data-type="tilCustomLink">Flu Vaccine: Why October Is A Good Time To Get Your Family Vaccinated</a>

Antibody studies suggest that people exposed to influenza last year may have antibodies that recognize the new mutation less effectively, particularly among teenagers and young adults.

Researchers at the Fred Hutchinson Cancer Center, including virologist Jesse Bloom, examined antibody responses to influenza A strains carrying mutations such as G155E.

In a preprint posted on bioRxiv, researchers tested antibodies from 260 people in Australia and the US against 148 influenza A strains that circulated through mid-2026. Some G155E-carrying strains were less readily recognized by antibodies, particularly those from younger people.

The researchers suggested that limited previous exposure to similar H1N1 variants could help explain this difference. However, laboratory findings alone cannot establish how likely people are to become infected or develop severe illness.

Flu Vaccine Guide: Best Time to Get Vaccinated & Side Effects | Doctors Explain

The mutation warrants monitoring, but current evidence does not establish that it makes the flu shot ineffective. How well this season’s vaccine protects against G155E remains uncertain.

Annual flu vaccination remains an important preventive measure, particularly for people at higher risk of complications. Regular hand hygiene and other basic precautions can also help reduce the spread of infections.

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Scientists have identified a new H1N1 mutation, G155E, in US flu samples, raising questions about immunity and vaccine protection as the flu season begins early.Early laboratory findings suggest the mutation may make some H1N1 strains harder for existing antibodies to recognize. However, the vaccine’s effectiveness specifically against G155E remains uncertain, and there is no evidence yet that the mutation makes the flu shot ineffective.H1N1 Becomes The Dominant Flu Strain In USAccording to the US Centers for Disease Control and Prevention’s (CDC) October 2 report, 53 of 55 influenza A samples undergoing subtyping were H1N1, while two were H3N2. No influenza B viruses were reported in this group.Researchers at the University of Washington identified G155E in 13 of 17 sequenced H1N1 samples collected from hospitals and clinics in the Seattle area.Could G155E Affect Flu Shot Effectiveness?Also read: Flu 2026: Symptoms To Watch For As New Season BeginsThe 2026-2027 flu vaccines approved by the US Food and Drug Administration target H1N1, H3N2 and an influenza B virus.Dr. Jennifer Duchon, a pediatric infectious disease expert at Mount Sinai Children’s Hospital, told Reuters that younger people may have had limited exposure to this year’s H1N1 strain.“What people are a bit worried about is that the H1N1 strain this year hasn't been seen by a lot of younger folk, so it may be more severe in them,” she said.However, this concern does not establish that G155E causes more severe disease. Flu vaccine effectiveness varies by season and depends partly on how well vaccine strains match circulating viruses. Scott Hensley, a microbiologist at the University of Pennsylvania, told Reuters that two of this season’s three vaccine components appear well matched to circulating strains. He also recommended getting vaccinated early.The American Medical Association also recommends annual flu vaccination for people aged six months and older, unless they have a medical reason not to receive it.G155E: Who Could Be More Vulnerable?Read More: Flu Vaccine: Why October Is A Good Time To Get Your Family Vaccinated Antibody studies suggest that people exposed to influenza last year may have antibodies that recognize the new mutation less effectively, particularly among teenagers and young adults.Researchers at the Fred Hutchinson Cancer Center, including virologist Jesse Bloom, examined antibody responses to influenza A strains carrying mutations such as G155E.In a preprint posted on bioRxiv, researchers tested antibodies from 260 people in Australia and the US against 148 influenza A strains that circulated through mid-2026. Some G155E-carrying strains were less readily recognized by antibodies, particularly those from younger people.The researchers suggested that limited previous exposure to similar H1N1 variants could help explain this difference. However, laboratory findings alone cannot establish how likely people are to become infected or develop severe illness.   Should You Worry About G155E?The mutation warrants monitoring, but current evidence does not establish that it makes the flu shot ineffective. How well this season’s vaccine protects against G155E remains uncertain.Annual flu vaccination remains an important preventive measure, particularly for people at higher risk of complications. Regular hand hygiene and other basic precautions can also help reduce the spread of infections.

g155e h1n1 mutation in us raises concerns: can this year’s flu shot still protect you?

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G155E H1N1 Mutation In US Raises Concerns: Can This Year’s Flu Shot Still Protect You?

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G155E H1N1 Mutation In US Raises Concerns: Can This Year’s Flu Shot Still Protect You?

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