Vaccines are gradually becoming more widely available across the United States. But as the fight to ensure everyone can access them continues, the US is also entering the second phase of its vaccination campaign against Covid-19: the fight against vaccine hesitancy.

About 26 percent of Americans say they won’t take a vaccine, according to an April 21-26 CNN poll. Getting the pandemic under control in the US could be challenging without their buy-in.

Meanwhile, in the United Kingdom vaccine hesitancy sits much lower; government polling shows it’s around 6 percent. This is not necessarily because the British are inherently more enthusiastic about vaccination. Last summer, a poll found that 75 percent of Americans and 71 percent of British people were open to taking a vaccine if one existed and was recommended by their government.

But in the year since then, vaccine hesitancy in the US has stayed about the same, while vaccine hesitancy in the UK has plummeted to the lowest in the world. The UK has administered 75 doses per 100 people, and 95 percent of people over age 50 have gotten their first vaccine dose. To be clear, the US vaccine effort has been going well, too. But there is growing concern that hesitancy might keep the country from reaching herd immunity and slow progress toward normalcy. The UK, apparently, doesn’t face that same challenge.