Moderna

As the Food and Drug Administration weighs approval of COVID-19 vaccinations for children under age 5, Florida Surgeon General Joseph Ladapo is opposed to the potential change.

The "bivalent" vaccine — meaning it targets two different antigens — is Moderna's leading candidate to have an effective booster ready for fall of 2022, the company said.

The company says a low-dose version of its vaccine triggers an immune response in children ages 6 months to less than 6 years equivalent to what has protected older children and adults.

Health officials argue the protection of the COVID vaccine booster wanes over time and say some people need a second booster. But other infectious disease experts say three shots are enough for now.

No deaths were reported in tests, and there were no signs of myocarditis, or heart inflammation, as a side effect.

If approved, this would be the second booster shot Moderna has issued for people ages 18 and up.

The consensus has been that Pfizer and Moderna are most protective. But a study looking at 5 vaccines — including Russia's Sputnik V and two Chinese types — offers an unexpected finding.

Some countries are moving ahead with plans to offer a fourth dose of COVID-19 vaccine. But studies are raising questions about the potential advantages of this extra booster.

Though people who are vaccinated and boosted appear to be better protected against omicron, the highly contagious variant has still led to breakthrough cases and a surge in infections worldwide.

Now, both the Pfizer and the Moderna booster shots can be given five months after the second dose of vaccine — down from six months.

Moderna says the FDA is looking into reports of a rare side effect — myocarditis, or the inflammation of the heart muscle — in those who've gotten the shot.

The U.S. has pledged to deliver 1.1 billion doses of COVID vaccines to countries in need. Billions more are needed. NPR interviewed the State Department's global vaccine coordinator to learn more.