Federal health officials on Wednesday urged Americans to consider wearing two masks as one of several strategies to better protect themselves against the threat of new and more contagious variants of the coronavirus.

“We know that universal masking works,” said John T. Brooks, medical officer for the Centers for Disease Control and Prevention’s covid-19 response. “And now these variants are circulating … whatever we can do to improve the fit of a mask to make it work better, the faster we can end this pandemic.”

Two methods substantially boost fit and protection, according to a CDC report and guidance released Wednesday. One is wearing a cloth mask over a surgical mask. The second is improving the fit of a single surgical mask by knotting the ear loops and tucking in the sides close to the face to prevent air from leaking out around the edges and to form a closer fit.