The first mRNA-based flu vaccine, Moderna’s mFlusiva, is now available in the United States, but it is only approved for adults aged 50 and older. The vaccine uses messenger RNA (mRNA) technology, similar to the one used in Moderna and Pfizer’s Covid-19 vaccines. The U.S. Food and Drug Administration (FDA) granted full approval for the vaccine for people aged 50 to 64 and accelerated approval for those 65 and older. This means that while the vaccine is approved for all adults 50 and older, Moderna must conduct further trials for the 65+ group. The Centers for Disease Control and Prevention (CDC) has not yet begun tracking flu cases for the upcoming season but advises people to get vaccinated by the end of October. In a late-stage clinical trial published in the New England Journal of Medicine in May, mFlusiva was found to be about 27% more effective than a standard flu shot. The vaccine is a trivalent shot, meaning it targets two strains of the influenza A virus and one strain of the influenza B virus, similar to traditional seasonal flu vaccines. However, unlike traditional flu shots, which use a weakened form of the virus grown in eggs, mFlusiva uses a small piece of genetic code (mRNA) to train the immune system to recognize and fight the flu virus. The mRNA is then broken down by the body and does not remain in the system. The FDA initially had concerns about the trial design when comparing mFlusiva to a standard-dose flu shot in people 65 and older. This is because the CDC typically recommends a high-dose flu shot for that age group. However, the FDA approved the vaccine with the condition that Moderna conduct a post-approval trial. An independent vaccine advisory panel also unanimously supported the vaccine’s approval for older adults. People under 50 cannot receive mFlusiva this season and must use other flu vaccines approved for their age group. It is important to note that mFlusiva is not designed to protect against Covid-19 and is separate from Moderna’s combination vaccine for both flu and Covid-19, which was approved in Europe earlier this year. Insurance coverage for mFlusiva is expected to be available from most private insurers, but it is unclear how widely Medicaid will cover it, as the program usually requires a formal recommendation from the CDC’s vaccine advisory committee. Medicare, on the other hand, is required to fully cover the cost of FDA-approved seasonal flu shots. Without insurance, the vaccine costs about $171 per dose, though some pharmacies may offer it for as low as $154. The availability of mFlusiva depends on local pharmacy stock and delivery schedules. Moderna has started shipping doses nationwide, and both CVS Health and Walgreens have confirmed availability. However, Walgreens expects to have only limited quantities this season. Some pharmacists have noted that demand for mFlusiva is currently low, as most people tend to wait until October to get vaccinated.