A decade after a landmark study proved that feeding peanut products to young babies could prevent development of life-threatening allergies, new research finds the change has made a big difference in the real world.

Peanut allergies began to decline in the U.S. after guidance first issued in 2015 upended medical practice by recommending introducing the allergen to infants starting as early as 4 months. The rate of peanut allergies in children ages 0 to 3 fell by more than 27% after guidance for high-risk kids was first issued in 2015, and by more than 40% after the recommendations were expanded in 2017.