For masks to be effective, they must be positioned over the nose and mouth and fit snugly along the sides, with no gaps showing.
That's step one, according to the American Academy of Pediatrics.
The next step is to use it consistently.
"Consistent use of a face mask is one part of a comprehensive strategy... to mitigate risk and help reduce the spread of COVID-19," said a statement on mask recommendations from the AAP, "particularly in those who are not fully vaccinated or not eligible to receive a COVID-19 vaccine."
Other parts of that strategy include vaccination, social distancing, and handwashing, to name a few.
So what type of mask is best? According to Dr. Edith Rosvely Brancho Sanchez, cloth is fine, "as long as your mask is fitting well."
"As long as the mask is taut and you have a good fit at the top and at the bottom you can keep washing it and wearing it," said the pediatrician, who treats patients at the Columbia University Irving Medical Center.
The World Health Organization recommended that for children who are generally in good health, there's no need to wear a medical-grade KN95 mask. A fabric mask should sufficiently keep the virus from spreading, as long as the mask is sized correctly and properly covers the nose, mouth and chin.
However, the WHO said for kids who do have underlying health conditions, a medical mask may be necessary. It's recommended to have a conversation about this with the child's doctor.