A new kind of flu vaccine is set to roll out soon for older adults. On Aug. 5, the Food and Drug Administration approved Moderna’s mRNA influenza vaccine, mFlusiva, for people ages 50 and up. the vaccine is expected to be available in local pharmacies in the U.S. for the 2026-2027 flu season, which typically starts in October.
The Moderna shot was shown to be more effective than the standard flu shot in a trial of more than 40,000 adults ages 50 to 64: Those who received the new vaccine were 27% less likely to get the flu. At the same time, those who took the mRNA vaccine reported more side effects, particularly injection-site pain, fatigue and headaches.
While all adults aged 50 and older can get the shot once it reaches the market, the FDA accelerated its approval for use in people 65 and older: Moderna must still complete a study of how well the vaccine compares with existing flu vaccines for this age group. Moderna also has a study underway in younger adults and a separate one for those ages 9 to 17. But the timelines for all pediatric studies extends as far as 2031, meaning that at least some groups may not receive the vaccine before then.
Despite the promising results of the adult studies, the vaccine may face some other barriers to wide acceptance: Only 30% of adults over 50 think that mRNA vaccines are generally safe, according to polling last year by KFF, a health policy nonprofit. Even among Democrats, only 48% said they were confident of their safety.
Vaccine experts link such doubts to what they see as the unfair criticism that has been focused on mRNA vaccines ever since they were the first approved for use against COVID-19. Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine skeptic, has been particularly dubious about the technology, and in 2025 canceled nearly $500 million in funds for development of mRNA vaccines.
Vaccine researchers say that mRNA vaccines has been shown to be safe and effective, citing comprehensive reviews of the technology.
“These concerns are inaccurate and not factual,” Dr. Stephen Thomas, director of the Global Health Institute at Upstate Medical University in Syracuse, said in an email. “Some people will just continue to not want to adopt this technology, but I believe the clinical data should speak for itself.”
To break down the basics on the new vaccine — and address the confusion and misinformation surrounding mRNA technology — we spoke with Dr. Sharon Nachman, the division chief for pediatric infectious disease at Stony Brook Children’s Hospital on Long Island, where she sees patients and conducts clinical research. Edited excerpts of the conversation are below.
Epicenter NYC: Why is this new mRNA flu vaccine better than our current flu vaccine?
Dr. Nachman: Our current flu vaccines, despite using them for many decades, are suboptimal, for a few reasons.
The first is that we have to predict which flu strains — and always more than one flu strain — will circulate in our winter season based [in part] on what’s circulating in the Southern Hemisphere. That means we have to predict six to eight months ahead of time what’s going to happen in our winter. Sometimes the [strain we’re predicting can be spot on, sometimes it’s not].
The next problem with that flu vaccine, the one that we’ve had for decades, is that it has to be grown in eggs. And the difficulties of growing flu virus in eggs makes making a vaccine from that product incredibly difficult, because sometimes the flu virus doesn’t grow in the eggs, sometimes it grows in the eggs and kills the eggs, so we can’t extract flu virus to make vaccine out of it.
This new flu product avoids problem one and problem two. It avoids having to guess eight months ahead of time which will be the circulating vaccine viruses, the variants, because it can be made in almost real time, looking at closer to the time what are the viruses that are circulating.
The second is the technology that is needed to make mRNA vaccines is instantaneous. You take the flu virus, you break it out into little pieces, and you can make messenger RNA so that your body makes antibodies quickly.
Epicenter NYC: What does the mRNA do once it’s in the body?
Dr. Nachman: mRNA is a signal. It tells your body, “OK, make an antigen.” It’s a script given to yourself about what to do next. It can’t change your DNA. People have this idea that it changes DNA. No, it’s messenger RNA – it just brings you a message. What you do with the message is up to you. So that’s a messenger RNA technology.
That’s very, very different than [with the traditional flu vaccine] me giving you an antigen, a piece of the virus, and telling your body, “Go ahead and make an antibody to it.”
Epicenter NYC: But isn’t that a message to your body in a way as well?
Dr. Nachman: It is, but it’s a different script, a different language. Messenger RNA is a much faster message to yourselves.
Epicenter NYC: Once the mRNA is in the body, does it stay in the body or is it broken down?
Dr. Nachman: No, the message is read and the paper is ripped up. It’s broken down quickly because that’s what your cells do all the time.
It doesn’t just sit around there for eons because you would then be making the same message all the time. That’s what cancer cells do. Remember, cancer cells don’t know how to stop reading a message. They keep reading the message or making the message. And that’s why this mRNA technology works so well in cancer cells, because it says stop reading that message.
Epicenter NYC: And you would still need this mRNA vaccine seasonally, the way you do the standard vaccine?
Dr. Nachman: Correct. Which is perfectly fine because there’s a new virus next year coming down the pike.
Epicenter NYC: Should people think of this as a complete replacement for the traditional flu shot or as another option?
Dr. Nachman: I think it’s another option, but it’s a much better option.
Epicenter NYC: Is there any reason someone who qualifies for the mRNA vaccine would choose a traditional flu vaccine instead, or that you would recommend it?
Dr. Nachman: At this point I would not think so. If you said to me, “I’m allergic to mRNA vaccine; in the past I got one and I can’t” — OK. If you said to me, there was some other issue with it that we’re not appreciating right now, OK.
It’s not like I’m giving you the flu virus. This is not a live vaccine. Is it possible that someone has some underlying immune issue that [means] they can’t take it? Maybe — [and if so] they should talk to their doctor.
But for the American general public, this is probably a much better vaccine. Because you’re closer to the circulating strains out there and that makes a big difference.
Epicenter NYC: Do you expect other doctors to recommend mRNA vaccines, and that it will eventually become the standard flu vaccine?
Dr. Nachman: I suspect that mRNA vaccines will replace the standard technology because at the end of the day, if you’re getting a vaccine, you’re actually going to want the better product. But that might happen over time.
Epicenter NYC: What do you think would be the incentive for some folks to take the standard flu vaccine, or for doctors to recommend it for someone who’s otherwise eligible for the mRNA vaccines?
Dr. Nachman: It’s going to be about trust. I also don’t know the pricing or insurance coverage for it, so that may be an issue also. This is a great question to bring up with your physician and check your insurance.
Epicenter NYC: Why start with adults 50 and older? What is it about that group that’s considered vulnerable?
Dr. Nachman: Older adults are the ones who get sickest with the flu, because they come to us with underlying comorbidities, etc. If we’re going to see a signal that this is a better vaccine, you go to the population that gets the sickest more often.
Epicenter NYC: Because people associate mRNA so strongly with COVID-19 vaccines, what questions or concerns have you heard from patients?
Dr. Nachman: There was the whole question about cardiac side effects from mRNA [COVID-19] vaccines. And the answer was they were mild.
These side effects did not last long. It was a younger population, not the older population. And more importantly, those side effects were quite similar to the immune response side effects that same group experienced when they got COVID. In other words, when they were not vaccinated.
Epicenter NYC: What are some of the most common misconceptions you’re expecting to hear about this mRNA vaccine?
Dr. Nachman: I think one is that, “oh, it’s changing my DNA.” That can’t happen. And understanding that messenger RNA, once it’s read, is [broken down quickly in the body].
Epicenter NYC: How much of the perception around the mRNA vaccine do you think is complicated by the experience of COVID-19 and misinformation around the COVID-19 vaccine?
Dr. Nachman: Unfortunately, I think the majority of it is. And the unwillingness to hear what mRNA science is, is our biggest problem.
In other words, it’s one thing to be scared, and I appreciate that, when something new comes by, a new medicine, new vaccine, you’re scared. That’s OK. And then you hear misinformation and that ratchets up your fear, and I understand that.
The most important thing you could do is listen because the solution to fear is knowledge. And it’s not safe, it’s not healthy to sit and fear when actually you could understand the real information and that would put your fears at rest.
Epicenter NYC: What do you think doctors and scientists can do differently this time to build trust?
Dr. Nachman: It really gets down to, it’s a one-by-one kind of thing, and talking about, “Here’s your 10th-grade biology teacher. Let them explain it to you, not me.”
It’s really all about talking to families in a language they hear and understand. If you don’t trust the fancy scientist and the academic center that you don’t know, go back to 10th grade. That’s what you learned in school. Those facts are still true now. They didn’t change.
Epicenter NYC: Are there any lessons from the COVID-19 vaccine rollout, including confusion around safety, around pregnancy, around changing recommendations, that public health officials should also consider now when they’re communicating about this vaccine?
Dr. Nachman: The problem is data does not settle people’s fears. Only people do. So I think our better way of solving this is having community talk to community. Having people who got the vaccine say, “No, it didn’t change my DNA.” People who did not get the vaccine saying, “I wish I had got the vaccine.” And people who got the vaccine and didn’t have side effects explaining how they felt.
Epicenter NYC: How should people separate the political debate from the underlying science of mRNA technology?
Dr. Nachman: It’s really important to understand who is the best advocate for you and your family medically. And the answer is it’s your physician. That’s really who it is.
I tell families, when you have a very fancy car and it makes that funny noise, are you going to go to Joe Mechanic? Or are you going to go to the expert in your car, the fancy car person whose only expertise is in your car? And the answer is, you paid a lot of money for that car. You’re going to go to the expert. Why would you do differently about your health and your child’s health?
