• Confidence in the coronavirus vaccines grew among U.S. adults late last year, with nearly half of Americans indicating in December that they would likely get vaccinated, according to a new CDC study.
• When people who said they were somewhat likely to get vaccinated were included in the count, confidence grew to as high as 68% in December.
• However, confidence differed between demographics, with younger adults, women and Black people, among others, reporting less trust in the shots.

Confidence in the coronavirus vaccine increased among U.S. adults late last year, with nearly half of Americans saying they would likely get vaccinated once the jab is available to them, according to a new federal study published Tuesday.

Before shipments of Covid-19 vaccines from Pfizer-BioNTech and Moderna began making their way to the arms of millions of Americans across the U.S. in December, national polling suggested that many adults were hesitant to get inoculated against the disease.

According to the new study from the U.S. Centers for Disease Control and Prevention, only 39.4% of adult Americans surveyed in September said they were absolutely certain or very likely to get vaccinated. However, that number increased to just over 49% by December as the drugs were granted emergency authorization by the federal government, the CDC found.

When people who said they were somewhat likely to get vaccinated were included in the count, confidence grew to as high as 68% in December. Trust in the drugs grew the most among adults age 65 and older, who have been some of the first Americans in line to receive the shots.

Between September and December, fewer people said they didn't intend to get a vaccine once it's available; "vaccine nonintent" decreased from 38.1% to 32.1%, the study found.

However, confidence differed between demographics. Younger adults, women, Black people, people living in nonmetropolitan areas, and those with lower educational attainment were more likely to say they didn't want the vaccine. People with lower income and those without health insurance also said they didn't intend to get vaccinated, according to the study.

"Although confidence in COVID-19 vaccines increased during September–December 2020 in the United States, additional efforts to tailor messages and implement strategies to further increase the public's confidence, overall and within specific subpopulations, are needed," researchers said in the study.

The CDC surveyed more than 3,500 adults in September and more than 2,000 adults in December. Only 123 people completed both surveys in September and December, according to the study.

So far, the U.S. has delivered more than 59 million doses of Covid-19 vaccines and has administered just over 42.4 million doses, according to recent data from the CDC. A separate study published Feb. 1 found that most of the nearly 13 million people given at least one shot of a Covid-19 vaccine within the first month of the drugs' distribution were women, age 50 or older and likely non-Hispanic and White.

Scientists have warned that new and highly contagious variants of the virus could require more people to be vaccinated to achieve so-called herd immunity. Dr. Jay Butler, the CDC's deputy director for infectious diseases, previously told the Infectious Diseases Society of America that current modeling suggests that 70% to 75% of people would need to be vaccinated for the population to reach herd immunity.

However, if a faster-spreading virus were to become the dominant strain, it would likely push that percentage to as high as 85%, he said.

Earlier on Tuesday, representatives from the White House Covid-19 task force announced they would begin shipping doses of Covid-19 vaccines directly to community health centers to boost equitable access to the shots.

The program, which is in addition to doses sent directly to states and pharmacy chains, is intended to expand vaccine supply to some of the hardest-hit communities, such as people who are homeless, agricultural migrant workers, residents of public housing and those with limited English proficiency, said Dr. Marcella Nunez-Smith, chair of the White House's Covid-19 Health Equity Task Force.

"Equity is our North Star here," Nunez-Smith said during a press briefing. "This effort that focuses on direct allocation to the community health centers really is about connecting with those hard-to-reach populations across the country."