A new medicine that can help infants avoid hospitalization due to respiratory syncytial virus (RSV) has been in short supply as cases of the illness surge in some parts of the country.

The CDC announced that an additional 770,000 doses of a monoclonal antibody treatment, which can be given to babies shortly after birth, are being sent to doctor’s offices and hospitals. The drug is sold under the brand name Beyfortus and can reduce the risk of serious complications from RSV by as much as 75%, the FDA indicated in its July approval announcement.

The preventive treatment is considered a breakthrough because RSV hospitalizes between 1% and 3% of all babies under 1 year old annually. Most children have been infected with RSV by the time they are 2 years old.

Usually, symptoms are mild, such as a runny nose and fatigue. But for some, the virus can lead to pneumonia or bronchiolitis, a dangerous lung condition that causes wheezing and makes it hard to breathe, the CDC says. In severe cases, babies need to be admitted to the hospital to receive additional oxygen, fluids due to dehydration, and sometimes even have a breathing tube inserted or get help breathing from a machine called a mechanical ventilator.

The announcement of additional doses of Beyfortus comes as some areas report overwhelming rates of RSV. In Texas, Cook Children’s Medical Center in Fort Worth posted on Facebook recently that people should expect long wait times at its emergency room as hundreds of people seek care there daily, and the RSV positivity rate reached 33%.

“Many infants are suffering from severe RSV with hospitals struggling to find beds for them all,” read an announcement from Cook Children’s that was published in Spanish. In central North Carolina, a spike in RSV cases prompted the Cone Health system to begin requiring masks and banning children ages 12 and under from visiting vulnerable areas, such as labor and delivery wards and neonatal intensive units, at one of its hospitals and also at a medical center.