"Those could be points of confusion in the week ahead as people try to figure out, 'Where am I in line?' " said Dr. Kelly Moore, associate director of immunization education at the Immunization Action Coalition.

--Melanie Evans contributed to this article.

Write to Jared S. Hopkins at jared.hopkins@wsj.com and Arian Campo-Flores at arian.campo-flores@wsj.com

(END) Dow Jones Newswires

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