At the start of the flu season, the current strain may signal a risk to young people; doctors ask for injections

NEW YORK — Doctors are urging Americans ages 6 months and older to get flu shots after an early and unusual surge in cases on the West Coast that virologists are still working to understand.

It could be the strain itself. The predominant flu strain this year is H1N1, which caused the 2009 swine flu pandemic and is now an integral part of the flu vaccine. But this year’s version of the virus has a new mutation called G155E.

People who have already been exposed to H1N1, either through infection or vaccination, would only benefit from some “residual protection against older versions”, the scientists say.

“What people are a little concerned about is that this year the H1N1 strain hasn’t been seen by a lot of young people, so it might be more serious in them,” said Dr. Jennifer Duchon, a pediatric infectious disease expert at Mount Sinai Children’s Hospital in New York, adding that her hospital has started seeing cases of the flu.

The 2026-2027 flu vaccines, approved by the FDA in August, target H1N1, H3N2, the dominant strain of last flu season, and an influenza B virus.

Although most children recover, the flu can be deadly, especially among younger children and those with underlying health conditions.

Promotion of flu shots has been scaled back under Health Secretary Robert F. Kennedy Jr., a longtime anti-vaccine activist who engineered an overhaul of long-standing childhood immunization schedules.

The American Medical Association recommends the injection for everyone 6 months and older.

Vaccine effectiveness varies depending on its compatibility with circulating flu strains months in advance. Over the past 10 years, it has been between 30% and 60% effective in reducing hospitalizations and deaths from the flu. Last year, an estimated 32 million Americans had the flu, 390,000 were hospitalized, and 24,000 died.

Scott Hensley, a microbiologist at the University of Pennsylvania, said two of the three components of this year’s vaccine appear to be very well matched to circulating flu strains.

However, the H1N1 mutation could affect antibodies in younger people, and with flu season accelerating, “it’s probably a good idea to get vaccinated early,” Hensley said by email.

Geographic changes

Typically, flu cases start in the Southern states and move north. This year, it’s coming from the west, said Caitlin Rivers, an epidemiologist at Johns Hopkins who tracks pathogens in a weekly newsletter called Force of Infection.

“I don’t have any clear reason why that would be the case,” Rivers said.

As last year was dominated by H3N2, there could be an “immunological gap” as immunity to the H1N1 virus is not as recent. Or, it could be the new mutation, she said.

Jeanne Marrazzo, executive director of the Infectious Diseases Society of America, said studies of antibodies from people exposed to the flu last year found they did not recognize this new mutation. This was especially true for antibodies from adolescents and young adults.

Marrazzo said small studies are something to be aware of but shouldn’t be cause for alarm.

Decline in vaccinations, increase in flu cases

According to data firm IQVIA, some 58 million U.S. adults received a flu vaccine last season, a drop of more than 20% from the nearly 75 million in the 2019-20 season, the last season before the COVID-19 pandemic changed vaccination patterns.

About half of children were vaccinated against the flu last year, according to CDC data, compared to more than 60% in 2019-20.

Standard flu vaccines are made by GSK, Sanofi and CSL’s Seqirus unit. AstraZeneca makes a nasal spray inoculation called FluMist. A new mRNA vaccine from Moderna is also available.

Vaccine makers say demand has remained consistent with last year. Two pharmacists told Reuters that vaccination rates had not increased significantly.

What worries people a little is that this year, the H1N1 strain has not been seen by many young people, so it could be more serious among them.

–Dr. Jennifer Duchon, Mount Sinai Children’s Hospital

The Centers for Disease Control and Prevention dropped its recommendation for the shot for most children in early 2025, a decision that a court put on hold.

The CDC also dropped its ad campaign to promote flu vaccination in 2025, according to news reports.

Paul Offit, an expert in pediatric infectious diseases at Children’s Hospital of Philadelphia, said he believes vaccination rates have been affected by HHS’s decision to reduce promotion of flu shots, as well as statements by Kennedy himself.

“He did what he could to discourage flu vaccination,” Offit said.

Asked about public health messaging about flu vaccines this season, HHS spokesperson Emily Hilliard pointed to the CDC’s “Respiratory Illness Season Toolkit” on the agency’s website. He says vaccination is the most effective tool to prevent serious illness.

Flu activity is low but has been increasing since late August, according to CDC data.

Positive tests reported to the CDC from clinical laboratories last week hit a 10-year high for this time of year at 5%. ‌On the West Coast, this figure was 10.7%, ⁠compared to 0.5% a year earlier. At the peak of the flu, rates are around 30%.

The numbers are also high in eight Southern states, including Florida and South Carolina, according to Hopkins’ Rivers.

Contribute : Jennifer Rigby