What Moderna’s New mRNA Flu Shot Offers Adults 50 and Older

The 2026-27 flu season arrives with a new choice for protection: the first messenger RNA flu vaccine available in the United States. In August 2026, the FDA approved mFLUSIVA, Moderna’s mRNA-based vaccine, for adults 50 and older. The approval expands beyond traditional shots to include a vaccine that trains immune cells to recognize influenza by delivering genetic instructions rather than using a weakened virus. As the flu season peaks in the months ahead, health officials urge Americans to understand their options and get vaccinated before widespread transmission begins.

Flu poses particular risks for older adults. From 2024 to 2025, flu hospitalizations reached a 15-year high, with flu-related deaths clustering heavily in older age groups. The CDC estimates that 70 to 85 percent of seasonal flu-related deaths occur in people 65 and older, a consequence of age-related immune decline and chronic conditions that complicate recovery. For this reason, federal guidance emphasizes vaccination as the primary defense—especially before October ends.

How the mRNA vaccine differs

mFLUSIVA works by a different mechanism than traditional flu shots. Standard flu vaccines contain inactivated (killed) flu virus or viral proteins, which the body recognizes as foreign. mFLUSIVA, by contrast, delivers genetic instructions—messenger RNA—that direct a person’s own cells to produce flu-virus proteins. The immune system then builds antibodies against these proteins without any actual flu virus ever entering the body. The mRNA itself breaks down quickly and does not persist in the bloodstream.

This approach offers a manufacturing advantage. Traditional flu vaccines require about six months to produce because they rely on growing viruses in eggs. mRNA vaccines take only two to three months to manufacture, allowing public health officials to select flu strains closer to flu season based on emerging virus patterns. The 2026-27 flu vaccines—including mFLUSIVA—were updated to better match the flu strain that spread widely during the previous season.

The numbers
In a clinical trial of over 40,000 adults, about 2 percent of mFLUSIVA recipients contracted confirmed flu, compared with 2.8 percent receiving the standard-dose vaccine—a 27 percent relative reduction in risk.

Effectiveness and who should consider it

In clinical trials involving over 40,000 adults aged 50 and older, mFLUSIVA proved more effective than standard-dose flu shots. About 2 percent of vaccine recipients contracted confirmed flu, compared with 2.8 percent of those who received the standard vaccine. This represents roughly a 27 percent relative reduction in risk—a meaningful advantage, though not absolute protection.

For adults 65 and older, the FDA based approval partly on immune response data from nearly 3,000 participants, which showed mFLUSIVA generated stronger antibody levels than high-dose traditional vaccines. The agency noted that ongoing research will confirm clinical benefits in this older age group.

The vaccine is authorized only for adults 50 and older. Within that group, it serves as an option alongside other effective choices. For adults 65 and older, the CDC recommends preferentially receiving one of several higher-dose or adjuvanted vaccines: Fluzone High-Dose (a traditional inactivated vaccine), Flublok (a recombinant vaccine made without eggs), Fluad (an adjuvanted traditional vaccine). Adults aged 50 to 64 for whom standard-dose vaccines remain appropriate can also choose mFLUSIVA if they prefer.

Side effects and safety considerations

Common side effects from mFLUSIVA mirror those of other vaccines but appear somewhat more frequently. These reactions typically included injection-site pain, fatigue, headache, muscle or joint aches, and chills. The FDA characterizes most side effects as mild to moderate, and they generally resolve within two days.

Severe allergic reactions are rare but possible with any vaccine. Such reactions, if they occur, typically develop within minutes to one hour after injection. People with a history of severe allergic reactions to vaccine ingredients, those who have experienced Guillain-Barré syndrome after a flu vaccine, or anyone who has fainted with injections should discuss mFLUSIVA with a healthcare provider before proceeding. Pregnant women, those who are breastfeeding, and immunocompromised individuals should also consult their doctor.

The CDC estimates that 70 to 85 percent of seasonal flu-related deaths occur in people 65 and older.

Timing and access to the vaccine

The CDC advises that most people receive their flu vaccine during September or October to build immunity before flu spreads widely. It takes approximately two weeks after vaccination for antibodies to reach protective levels. Early vaccination during summer months is generally discouraged for older adults because immunity can wane over a long winter and spring season, though exceptions exist for pregnant women in their third trimester.

Vaccination remains beneficial throughout the flu season if someone misses the September-October window. However, delaying vaccination into November or later means waiting longer for immunity to develop while transmission risk increases.

Medicare Part B covers FDA-approved seasonal flu vaccines with no out-of-pocket cost for eligible beneficiaries. Most private insurers are expected to cover mFLUSIVA as well. Without insurance, mFLUSIVA costs approximately $171 per dose. CVS has begun stocking the vaccine, and Walgreens expects to receive shipments soon, though in limited quantities this season.

Who needs protection most

Everyone aged 6 months and older without contraindications should receive an annual flu vaccine, according to CDC guidance. This includes pregnant women, healthcare workers, and people who care for high-risk individuals. However, certain groups benefit from enhanced protection. Adults 65 and older face the highest risk of serious complications and death. People with chronic conditions such as asthma, diabetes, or heart disease, those with weakened immune systems, and residents of long-term care facilities also warrant priority attention.

The flu vaccine does not guarantee immunity, but it substantially reduces the risk of infection and typically lessens severity if infection occurs.

Photo: Bill Branson (photographer) · Public domain · via Wikimedia Commons