WASHINGTON - A planned booster shot campaign in the United States is dividing experts, as the Food and Drug Administration's vaccine advisory committee prepares to meet Friday for a nonbinding vote on whether the agency should approve a third dose of the vaccine developed by Pfizer and BioNTech. 

The experts will vote on whether a booster should be approved by FDA, but their recommendation is not binding. The agency typically follows the recommendations of its advisers.

The regulatory and political landscape for booster shots in the United States has been patchy. The Biden administration came out in strong support of giving booster shots to most Americans, and some states have begun preparing to distribute them as soon as next week. Immunocompromised people have been authorized to get booster shots since August - and many people with healthy immune systems have not waited for FDA approval to get theirs.

But the scientific community is split. Two senior outgoing FDA officials recently wrote a review with other scientists that was published in the Lancet medical journal, in which they argued that "current vaccine supplies could save more lives if used in previously unvaccinated populations than if used as boosters in vaccinated populations."

Then there are those who say it is immoral to give people third doses when nearly 58 percent of the world has not even had one. The World Health Organization recently called for a moratorium on booster shots until the end of the year - a call that the White House has characterized as a "false choice" and that several other rich countries have ignored.