WASHINGTON (AP) — U.S. health regulators have given full approval to Moderna's COVID-19 vaccine after reviewing additional data on its safety and effectiveness.

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The decision Monday by the Food and Drug Administration comes after many tens of millions of Americans have already received the shot under its original emergency authorization.

Full approval means FDA has completed the same rigorous, time-consuming review for Moderna’s shot as dozens of other long-established vaccines.

Pfizer's COVID-19 vaccine received full approval last summer.

Public health advocates initially hoped the distinction would boost public confidence in the shots.

But there was no discernable bump in vaccinations after the Pfizer decision.

Answers to 25 common COVID-19 vaccine questions

Vaccinations for COVID-19 began being administered in the U.S. on Dec. 14, 2020. The quick rollout came a little more than a year after the virus was first identified in November 2019. The impressive speed with which vaccines were developed has also left a lot of people with a lot of questions. The questions range from the practical—how will I get vaccinated?—to the scientific—how do these vaccines even work?

Keep reading to discover answers to 25 common COVID-19 vaccine questions.