Cutting Vaccine Doses Threatens to Create New Virus Strains

Sticking to the two-dose regimen Pfizer Inc. and Moderna Inc.'s vaccines could help shield against the creation of new variants by offering the fullest protection against the virus, Anthony S. Fauci said Monday.

President Joe Biden‘s chief medical adviser responded to questions over whether the U.S. should focus its distribution efforts on getting out the first dose and put less emphasis on the second one.

Lowering the level of protection in the community increases the chance the virus will mutate because it has a greater chance of spreading. Viruses can’t mutate if they can’t replicate in people.

“If you ...