With a third COVID-19 vaccine now authorized for emergency use, U.S. states are ramping up vaccination efforts to curb coronavirus transmission and the spread of variants.
The U.S. Food and Drug Administration (FDA) authorized Johnson &Johnson's COVID-19 vaccine for emergency use on Saturday.
A day later, the U.S. Centers for Disease Control and Prevention (CDC) recommended the vaccine to be administered for Americans 18 years of age and older.
It is the third COVID-19 vaccine and the first single-dose vaccine authorized in the United States.
The first doses of the Johnson &Johnson's COVID-19 vaccine were administered Tuesday as initial shipments reached states and vaccination sites.
The other two vaccines available in the country are developed by American drugmaker Pfizer in partnership with German company BioNTech, and by American drugmaker Moderna, respectively.
U.S. President Joe Biden said Tuesday the United States would have enough COVID-19 vaccine doses for every adult American by the end of May, which would dramatically accelerate his timeline previously set for the end of July.
Biden announced that Johnson &Johnson will partner with Merck to help accelerate its vaccine production. He hailed the partnership as a way to quickly jumpstart the sluggish vaccine production, likening it to cooperation between corporations during World War II.
Biden also announced he was directing states to prioritize teachers in their vaccine distribution plans in a bid to reopen schools.
While the country are accelerating vaccine efforts, some states, including Texas and Mississippi, plan to drop mask mandates and reopen all businesses at 100 percent capacity.
Biden on Wednesday called it a "big mistake" for states to end mask mandates.
Health experts have cautioned against states reopening too quickly.
The baseline level of coronavirus cases needs to fall further before the country can confidently resume normal activities, even as the vaccine rollout accelerates, said Anthony Fauci, the country's top infectious disease expert.
Fauci noted that in past periods of the pandemic, "when we started to pull back prematurely, we saw the rebound. We definitely don't want that to happen."
Experts are also concerned about some worrisome variants that are in places like California and New York.
CDC Director Rochelle Walensky said the variants appear to spread more easily and are contributing to a large fraction of current infections in those areas, adding urgency to the situation.
The variant in California, known as B.1.427/B.1.429, spreads more easily than its predecessors and is now dominant in the state, according to scientists at University of California, San Francisco.
In laboratory tests, it was shown to be less vulnerable to antibodies generated by COVID-19 vaccines or by prior infections, according to researchers.
The United States has recorded over 28.77 million cases with more than 518,900 related deaths as of Wednesday evening, according to the real-time count kept by Johns Hopkins University.
