WASHINGTON (AP) — A new global plan aims to end most cases of polio by late next year, and essentially eradicate the paralyzing disease by 2018 — if authorities can raise the $5.5 billion needed to do the work, health officials said Tuesday.

Part of the challenge will be increasing security for vaccine workers who have come under attack in two of the hardest-hit countries. And the plan calls for changing how much of the world protects against polio, phasing out the long-used oral vaccine in favor of a pricier but safer shot version.