The Food and Drug Administration announced Monday it had approved a new kind of immunization to protect babies from RSV, or respiratory syncytial virus. The drug, nirsevimab, is one of two new options doctors hope could soon prevent the leading cause of hospitalization facing American infants.

The Centers for Disease Control and Prevention issued a health advisory last month that respiratory syncytial virus, or RSV, is unexpectedly spreading in Southern states. RSV, which usually spikes during winter, can cause severe illness in kids and older adults and kills up to 500 children under age 5 each year.

Annual outbreaks of RSV occur in the late fall through early spring months, but in 2022, outbreaks began earlier than usual. The Centers for Disease Control (CDC) has issued a health advisory regarding higher instances of the virus and stressing the importance of preventative measures.

Today, the U.S. Food and Drug Administration approved Arexvy, the first respiratory syncytial virus (RSV) vaccine approved for use in the United States. Arexvy is approved for the prevention of lower respiratory tract disease caused by RSV in individuals 60 years of age and older.

In the most recent fortnightly data release, 6,356 infections were reported across the country. That's a slight increase from the previous fortnight, when 6,292 cases were reported. The database also shows that most cases were in children aged four or younger: that's 19,641 cases for 2023 to May 12, out of 32,259 total cases — almost two-thirds.