Fewer Americans are reluctant to get a COVID-19 vaccine than just a few months ago, but questions about side effects and how the shots were tested still hold some people back. That’s according to a new poll that highlights the challenges at a pivotal moment in the U.S. vaccination campaign. The survey by The Associated Press-NORC Center for Public Affairs Research finds that just 11% of people who remain unvaccinated say they definitely will get the shot, while 34% say they definitely won’t. That leaves a large swath of Americans in the middle who might still roll up their sleeves.