The Food and Drug Administration has approved a new drug from Merck designed to protect infants from respiratory syncytial virus, or RSV, a common but potentially serious seasonal illness.

Merck's shot will compete against a similar blockbuster treatment from Sanofi and AstraZeneca called Beyfortus.

The simplicity of Merck's monoclonal antibody for RSV in infants could be a plus in its competition with AstraZeneca's existing treatment.