What to Know About mFlusiva, the New mRNA Flu Vaccine

Sep 15, 2026 | Cold and Flu, Family Medicine, Featured, Infectious Diseases, Vaccines, Your Health

For the first time, adults age 50 and older in the United States can get an mRNA flu vaccine.

The U.S. Food and Drug Administration (FDA) approved mFlusiva®, the first mRNA flu vaccine, in August 2026. Moderna makes mFlusiva. It uses the same basic vaccine technology as mRNA COVID-19 vaccines. But it targets influenza.

Unlike traditional flu vaccines, mFlusiva does not contain a live or killed influenza virus, or pieces of the virus. Instead, it uses messenger RNA (mRNA). This gives temporary instructions to your immune system, your body’s natural defense system. The instructions help it learn to recognize influenza.

This new approach might even have an edge over traditional flu vaccines.

“There is some evidence that suggests mFlusiva may offer somewhat better protection against the flu than traditional flu vaccines,” says Rebecca Choudhury, MD, Assistant Professor of Medicine (Infectious Diseases), Icahn School of Medicine at Mount Sinai.

How does mFlusiva work? How well does it protect against the flu? What do we know about safety and side effects? Dr. Choudhury explains the new mRNA flu vaccine and gives advice on getting your flu shot.

Rebecca Choudhury, MD, Assistant Professor of Medicine (Infectious Diseases), Icahn School of Medicine at Mount Sinai

How does mFlusiva work, and how is it different from traditional flu vaccines?

Traditional flu vaccines show the influenza virus or parts of it to the immune system. This teaches the immune system to recognize and fight the virus later. Depending on the vaccine, that may mean a killed virus, a weakened virus, or pieces of the virus.

mFlusiva is an mRNA vaccine. It does not contain a living or dead virus. It also does not contain viral parts. The vaccine uses messenger RNA designed to produce influenza surface proteins called hemagglutinin.

An image of the mFlusiva mRNA flu vaccine. Image credit: Moderna

It’s the same basic principle used by mRNA COVID-19 vaccines. But the target is different. COVID-19 vaccines tell cells to make the coronavirus spike protein. mFlusiva tells cells to make an influenza surface protein.

“This flu vaccine is creating a different protein, but the principle of how it works is the same,” says Dr. Choudhury.

Is mFlusiva more effective than traditional flu vaccines?

In one trial in adults age 50 and older, about 2 percent of people who received mFlusiva developed influenza confirmed by lab testing within six months of vaccination. By comparison, 2.8 percent of people who received a standard-dose flu vaccine developed influenza. The mFlusiva group had a 27 percent lower rate of flu.

For adults 65 and older, there is an important caveat. People in this age group typically receive a high-dose or adjuvanted flu vaccine rather than the standard-dose vaccine used in this trial. An adjuvanted vaccine has an added ingredient that helps the vaccine work better.

Studies comparing the immune response to mFlusiva with a high-dose flu vaccine have been encouraging. Immune response means how the body reacts to a vaccine to build protection.

“However, a stronger immune response does not necessarily mean better protection against actually getting the flu,” Dr. Choudhury notes.

Another study is expected to directly compare clinical outcomes between mFlusiva and a high-dose flu vaccine in adults 65 and older.

Is mFlusiva safe? What are the side effects?

Clinical trials so far suggest mFlusiva has a safety profile similar to traditional flu vaccines for serious adverse events. These are harmful or unexpected medical problems or side effects.

In a trial comparing mFlusiva with a standard-dose flu vaccine, serious vaccine-related adverse events were very rare. They occurred at similar rates in both groups.

Researchers also looked closely at heart-related events because of concerns previously raised about mRNA COVID-19 vaccines.

One participant who received mFlusiva developed cardiomyopathy and pericarditis. These are two heart-related conditions. This happened about three months later. It was unclear whether the vaccine caused them. One participant in the traditional flu vaccine group also developed pericarditis.

Dr. Choudhury says current data do not show a higher risk of these events with mFlusiva than with traditional flu vaccines.

The main difference so far is short-term side effects. Injection-site reactions, headaches, body aches, and fatigue occurred more often with mFlusiva than with traditional flu vaccines. This was seen across multiple studies.

“These symptoms are generally relatively mild, they go away on their own without any sort of treatment,” Dr. Choudhury says.

What are the advantages of an mRNA flu vaccine?

“The advantages are less so in how the vaccine itself works, and more so in how the vaccine is made,” Dr. Choudhury says.

Each year, scientists must predict which influenza strains will circulate months before flu season. Traditional flu vaccines take several months to produce. That can make it hard to change the vaccine if the strains that circulate are different from those expected.

Because mRNA vaccines do not rely on growing influenza virus in a lab, they can be produced more quickly. Dr. Choudhury says this could give vaccine makers more flexibility. They can update an mRNA vaccine when an unexpected flu strain begins circulating.

That flexibility could help produce flu vaccines that more closely match the strains actually circulating. It could also potentially improve how well seasonal flu vaccines protect people.

Who can get mFlusiva, and who may want to consider it?

mFlusiva is approved for adults age 50 and older. Based on the evidence so far, Dr. Choudhury says adults ages 50 to 64 may have the clearest reason to consider it.

People ages 50 to 64 typically receive a standard-dose flu vaccine. That was the same type used in the clinical trial. The trial found a lower rate of influenza among mFlusiva recipients.

Dr. Choudhury says mFlusiva may be especially worth considering for adults ages 50 to 64 with long-lasting (chronic) health conditions. These conditions can raise the risk of severe influenza. They include high blood pressure (hypertension), diabetes, chronic kidney or liver disease, obesity, or chronic lung disease.

Adults 65 and older can also receive mFlusiva. However, researchers are still gathering stronger clinical evidence. The studies compare mFlusiva with the high-dose or adjuvanted flu vaccines typically recommended for this age group.

Still, choosing between vaccines should not stop you from getting vaccinated.

“Ultimately, the best flu vaccine is the flu vaccine that you can get,” Dr. Choudhury says. If mFlusiva is not easy to get, she recommends getting an appropriate flu vaccine from your doctor’s office, pharmacy, or workplace rather than going without vaccination.

Can an mRNA flu vaccine change your DNA?

No. The mRNA in mFlusiva cannot change your DNA. It also cannot become part of your genetic code.

Dr. Choudhury says this has confused some people. Some worry that mRNA could reprogram their genetic code. But that’s not how the technology works.

Like other mRNA vaccines, mFlusiva gives cells temporary instructions to make a specific protein. Here, that protein is an influenza surface protein. The mRNA is then quickly broken down by the body.

“The mRNA in mFlusiva cannot become part of your genome,” says Dr. Choudhury.

When should you get your flu shot?

Flu season typically begins around October. Infections often peak around December. But the timing can vary from year to year.

Your immune system needs about two weeks after vaccination to build protection. Dr. Choudhury recommends planning ahead. The same timing applies to mFlusiva.

“I typically get the flu vaccine myself around early October,” Dr. Choudhury says.

Getting vaccinated is important even if you don’t consider yourself at high risk for serious problems from the flu. Influenza can cause severe illness that requires a hospital stay. Even a less serious case can leave you sick in bed for a week or longer.

“Getting your flu shot is a very easy, safe and effective step you can take to reduce your risk of getting sick and reduce your risk of making others sick,” Dr. Choudhury says.

Have questions about the new vaccine? Talk with your doctor.

Here’s What You Should Know About the New Hepatitis B Vaccine Recommendation

Jan 5, 2026 | Children's Health, Family Medicine, Featured, Infectious Diseases, Pediatrics

For several decades, federal guidelines regarding hepatitis B vaccination for infants in the United States had been unchanged and consisted of a first shot given at birth, a second at 1-2 months, and a third at 6-18 months.

In December 2025, the Centers for Disease Control and Prevention (CDC) announced new recommendations for hepatitis B vaccinations. For infants born to mothers who test negative for hepatitis B, the agency recommended the initial shot only at two months or after, and for infants to undergo antibody testing to determine whether the second and third shots are needed.

“The medical community hasn’t changed its stance on hepatitis B vaccinations, however,” says Daniel Caplivski, MD, Professor of Medicine (Infectious Diseases) at the Icahn School of Medicine, and Director of the Icahn School of Medicine Travel Medicine Program.

Daniel Caplivski, MD, Professor of Medicine (Infectious Diseases) at the Icahn School of Medicine at Mount Sinai (left), and Roberto Posada, MD, Professor of Pediatrics (Infectious Diseases) at the Icahn School of Medicine at Mount Sinai (right).

“Hepatitis B is a virus that, for many people, once they get the infection, they have it for the rest of their lives,” says Roberto Posada, MD, Professor of Pediatrics (Infectious Diseases) at the Icahn School of Medicine at Mount Sinai. “It can lead to cirrhosis of the liver and liver cancer, both of which are very preventable through childhood vaccination.”

Why are medical experts recommending that infants receive hepatitis B vaccinations at birth and to receive all shots? Drs. Caplivski and Posada explain the rationale behind the schedule and other facts about the virus.

Why should babies be vaccinated for hepatitis B at birth?
Dr. Posada: This recommendation had been in place since 1991. There are a few reasons why medical experts had pushed for hepatitis B vaccination for infants at birth. Usually, we check pregnant women for hepatitis B. But some people might not have access to full prenatal care, or the check sometimes gets missed. A mother in that situation can unknowingly pass hepatitis B on to the child. Vaccination at birth can prevent that.

Another reason is that the opportunity to protect the child is highest at the moment of childbirth. Once a child and mother are discharged, they might not return for follow-up appointments, or do so at the appropriate times. Thus, giving the hepatitis B vaccination right at childbirth at least provides that initial protection.

What’s the risk of waiting to vaccinate infants for hepatitis B?
Dr. Posada: For infants, other than hepatitis B being passed from the mother, the virus can be transmitted to some degree through household exposure to someone who has hepatitis B. For example, sharing utensils, an infant putting a parent’s toothbrush in the mouth—these are not the main ways of contracting the disease, but they can happen. We want to vaccinate the kids in the event there is someone in the household with hepatitis B.

Other than for infants, the main way hepatitis B is transmitted is through sexual transmission or contact with contaminated blood, such as via needles. That’s another reason to vaccinate children before they become sexually active.

Is the hepatitis B vaccine effective at preventing transmission?
Dr. Caplivski: Ever since we adopted the practice of vaccinating infants at birth, the rate of infants and children contracting hepatitis B has dropped to practically zero.

And the success of vaccinating at childbirth has been replicated around the world. In China, after they adopted a three-dose vaccination schedule from birth, the prevalence of hepatitis B carriers under 5 years old fell from 10 percent to around 0.3 percent in 10 years. That’s a lot of lives saved from chronic complications of the disease.

What could be the consequences of contracting hepatitis B?
Dr. Posada: If a baby gets it at birth, they’re very likely to have it for the rest of their life. And because the infection is lifelong, the more chances for cirrhosis, liver failure, or liver cancer to develop in the lifetime. Someone who contracts it at an older age has a higher chance of clearing the infection from the body.

Dr. Caplivski: The long-term consequences of liver failure and cancer are incredibly difficult for a patient. It is a medically intensive disease, but it also has a huge impact on health care expenditures. All of these could be avoided through vaccinations at childbirth.

According to statistics from the CDC, about 9 in 10 infants who become infected go on to develop lifelong chronic infection. The risk goes down as a child gets older. About 1 in 3 children who get infected before age 6 will develop chronic hepatitis B. Approximately 15–25 percent of people with chronic infection develop chronic liver disease, including cirrhosis, liver failure, or liver cancer.
Is it safe for infants to be vaccinated at childbirth?
Dr. Posada: The vaccine is a recombinant vaccine—meaning it is not a live virus; it is only protein from the virus synthesized in the lab. It cannot cause infection. Other than discomfort at the time of injection, we have had decades of data showing that hepatitis B vaccination at childbirth is safe.
Would the new recommendation by CDC create any access changes?

Dr. Caplivski: Historically, insurers have used CDC recommendations to base their coverage of vaccinations. While the federal entity is retreating from actively recommending hepatitis B vaccinations at childbirth, don’t forget that state departments of health can have their own recommendations and intervene if needed. In the case of New York State, there has been no change in guidelines, and we are still actively recommending hepatitis B vaccinations at childbirth.

What the new CDC action might have caused is a worsening of vaccine skepticism. Even in that situation, it is worth speaking with your pediatrician and health provider to learn more about what is the right course of action for you and your child.

Dr. Posada: Besides talking to your pediatrician, there are other sources of information that are well trusted, such as the American Academy of Pediatrics. It has very good information about childhood vaccines. At the end of the day, as doctors, we want your children to be healthy too.

 

Is a Vegetarian Diet During Pregnancy Healthy?

Mar 16, 2015 | Diet and Nutrition, Family Medicine, Health Tips, Women's Health

During pregnancy, a woman is encouraged to follow a healthy lifestyle, including making dietary changes as needed. Women who are vegetarian may become confused about whether continuing their vegetarian diet is actually healthy. Many such women will hear from friends, family, and health care professionals that being vegetarian is “unsafe” for both mother and baby. This can leave them feeling seriously conflicted. For long-time vegetarians, it can be especially disheartening when being vegetarian is not simply a diet, but a lifestyle. (more…)

Typical Communication Development in Children, Part III (Ages 3-5)

Mar 2, 2015 | Family Medicine, Health Tips, Pediatric Care, Pediatrics, Speech Pathology

In previous posts, the benefits of parental familiarity with a growing child’s hearing, speech, and language development were discussed, specifically as guidelines for pediatricians and other health and education professionals with which to monitor the child’s progress or delay, and offer help if necessary. This final post in a three-part series will cover the basic benchmarks of communication for preschool-age children. (more…)

Typical Communication Development in Children, Part II

Nov 24, 2014 | Family Medicine, Pediatric Care, Pediatrics, Speech Pathology

If you are a parent, it is good to be familiar with the basic benchmarks for hearing, speech, and language development as a child gets older. The benchmarks serve as guidelines for pediatricians and other health and education professionals with which to monitor the child’s progress or delay, and offer help if necessary. In this second post of a three-part series, I will cover the basic benchmarks for toddlers. (more…)

Mental Health: It’s an important issue for kids too

May 8, 2014 | Family Medicine, Pediatric Care, Pediatrics

The Substance Abuse and Mental Health Services Administration (SAMHSA) and the U.S. Department of Health & Human Services have designated Thursday, May 8, 2014 as National Children’s Mental Health Awareness Day. The goal is to raise awareness about the importance of children’s mental health and that positive mental health is essential to a child’s healthy development from birth
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