Cars are lined up at the Covid-19 mass vaccination site at Dodger Stadium in Los Angeles, California on February 23. Mario Tama / Getty Images

More than half of Americans said they had already received at least one dose of the Covid-19 vaccine or were getting vaccinated as soon as possible, the Kaiser Family Foundation reported on Friday.

This was the result of a survey by the foundation 55% of U.S. adults surveyed have either received a shot or say they want to be vaccinated ASAP. That’s an increase of 47% in mid-January and 34% in early December. The KFF Vaccine Monitor report on Friday also showed that all populations surveyed are more keen to be vaccinated compared to December.

The KFF Vaccine Monitor survey, conducted February 15-23, included 1,874 adults with over-sampling of approximately 500 black adults and 500 Hispanic adults.

Black and Hispanic adults, and those between the ages of 18 and 29, are most likely to say they’d like to see how the vaccine works in public before receiving it. More than a third of black adults and 26% of Hispanic adults surveyed say they want to wait, compared with 18% of white adults surveyed.

The survey found 22% of respondents are either “definitely not” vaccinated or only given the vaccine when necessary for work, school or other activities. This is in line with the numbers posted in January and December, suggesting that this group holds firm views.

Republicans, key non-healthcare workers, and people living in rural areas most likely said they “definitely won’t” be vaccinated.

“While there has been greater overall buzz for COVID-19 vaccination, the demographics that are most enthusiastic, cautious and resilient remain similar to January,” the researchers wrote in the report.

Given the expected emergency approval from the US Food and Drug Administration for the Johnson & Johnson Covid-19 single vaccine, the survey found that about a quarter of people who would like to “wait and see” before vaccination said they would do more be likely to get a vaccine that only takes one dose.

The survey found that serious side effects are the number one concern people have about receiving the vaccine. More than half of people who have not been vaccinated share this concern.

About a third of people who were not vaccinated said they feared they might get Covid-19 from the vaccine – something that is biologically impossible – because they are working out of their own pocket due to side effects. These fears were more common among black and Hispanic adults.