FluMist, the only needle-free flu vaccine on the market, won a lukewarm recommendation from federal vaccine advisers Wednesday.

The nasal spray vaccine has been off the U.S. market for two years because it barely worked against one common strain of flu in kids. The company that makes it, MedImmune, says it has reformulated the vaccine and thinks it will work better next year.

“This is not an easy decision,” said Dr. Nancy Bennett, chair of the Advisory Committee on Immunization Practices (ACIP), whose decision guide which vaccines are available on the U.S. market.

ACIP voted 12-2 to add FluMist back to the mix of flu vaccines that doctors and clinics can use.

The vaccine experts on the committee weakened their usual recommendation to make it clear they were not ready to strongly endorse FluMist. They changed the wording to say it's up to doctors to choose.

There are several different formulations of influenza vaccine. FluMist is known as live attenuated influenza vaccine or LAIV. Injected vaccines use either inactivated virus — they’re called IIV for short — or genetically engineered (recombinant) virus, known as RIV for short.

“For the 2018-19 season, immunization providers may choose to administer any licensed, age appropriate, influenza vaccine (including LAIV, IIV and RIV). LAIV4 is an option for influenza vaccination for persons for whom it is otherwise appropriate,” the new recommendation reads.

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This wording puts FluMist on the “recommended” list, which means insurance companies have to pay for its use, without being a strong endorsement. FluMist never lost its approval from the Food and Drug Administration, but vaccine providers usually don't even make a product available unless it has an ACIP endorsement.

ACIP members voted against recommending injected vaccines over FluMist.

There is real worry among flu experts that the poor effectiveness of flu vaccines, especially this past season, may make Americans less willing to get it. The Centers for Disease Control and Prevention recommends that everyone over the age of 6 months get a flu vaccine every year, but fewer than half of all Americans do.

“There is potential for harm if the new formulation of (FluMist) is recommended and used and is not effective,” the CDC’s Dr. Lisa Grohskopf, who is not a member of ACIP and who led a team reviewing FluMist’s past effectiveness, told the committee.

Two panel members said they were worried about hurting children and further undermining the public’s perception of the safety of flu vaccines if FluMist comes back on the market and does not work well.

“I have real mixed emotions about this because I think we want to protect as many people as we can, particularly, as a pediatrician, for children,” said Dr. Henry Bernstein, a professor of pediatrics at Cohen Children’s Medical Center in New York.

But others said they were equally worried that kids are not being vaccinated against flu because the needle-free option is not available, and they noted that FluMist is clearly better than not getting vaccinated at all. It works well against H3N2 flu virus, which has been the dominant virus making people sick during the current severe flu season.

“It’s better than nothing,” said Dr. Grace Lee, a professor of pediatrics at Stanford University School of medicine.

(ACIP) declined to recommend FluMist in 2016 and again for this season, citing studies that showed it only reduced the risk of getting influenza by 3 percent over the past three flu seasons. It’s been off the U.S. market since then, although it is still used in other countries, including Canada and the European Union.

Grohskopf said a thorough CDC review confirmed FluMist did not work well against H1N1 in recent years, although it was effective against the other flu strains.

AstraZeneca, which makes FluMist at its MedImmune subsidiary outside Washington, D.C., said it reformulated the H1N1 component of the vaccine and presented evidence that it now works better.

But Grohskopf pointed out that no one can know that until there’s a flu season in which H1N1 is the dominant strain. This past year, H3N2 has dominated. The CDC says influenza has killed 84 kids so far this year and says H1N1, H3N2 and influenza B strains have all killed children.

“None of us knows what is going to happen,” she said.

All flu vaccines are a cocktail, made using three or four strains of the most common circulating flu viruses. They must be reformulated every year for the upcoming influenza season.

FluMist is a little different from other vaccines because not only is it spritzed up the nose, but it uses “live” flu virus. For that reason, some kids, such as those with asthma, usually cannot be administered FluMist, anyway.

AstraZeneca says it will supply FluMist to the U.S. market next season.