In May of last year, the U.S. government announced Operation Warp Speed, an initiative aiming to speed up the production and administration of COVID-19 vaccines. Seven months later, and the Food and Drug Administration, or FDA, cleared two COVID-19 vaccines — one produced by Pfizer-BioNTech and one produced by Moderna — for emergency-use authorization. Finally, the 20 million Americans that the Operation hoped to reach before the year’s end could be vaccinated.

But that’s not what has happened. Since the two vaccines were approved in mid-December, only 2.1 million people in the United States have been vaccinated, despite 14 million vaccine doses having been distributed across the country.

Most frustrating of all the reasons that vaccine administration stalled — snowstorms, holidays, inexperience with pandemic response — is people’s hesitancy to take it. Despite leading the world in both total cases (more than 25 million) and deaths (more than 419,000), just 65% of Americans say they would take the vaccine today if it were free of charge. While this figure represents the most support among Americans for a vaccine dating back to the polio vaccine in the 1950s, it’s only average when compared to the international community. Furthermore, even though 65% population vaccination falls in the range of early estimates needed to achieve herd immunity, many experts now believe a percentage closer to 90% vaccination is more accurate.

One significant contributor to vaccine hesitancy seems to be intense partisan division. Following the results of the 2020 election, Democratic confidence in the vaccine rose sharply while Republican confidence waned slightly. A recent Gallup Poll found that 83% of Democrats were willing to receive the vaccine but just 45% of Republicans expressed the same sentiment. Prior to the election, Democratic trust in the vaccine sat at 53% while Republican trust was at 50%. This drop might be attributed to former president Donald Trump’s promise to deliver the vaccine by Election Day, which caused many Democrats to feel the scientific process was being excessively rushed. Thus, the restoration of faith in the vaccine could be a byproduct of election results, signaling confidence that a new administration would more seriously respect the scientific process.

This data seemingly reflects the effects of President Trump’s past political rhetoric. Among those Americans unwilling to take the vaccine, 21% say their primary reasoning is “not [being] enough at risk from COVID-19,” and 19% oppose vaccines in general. Both of these sentiments have been echoed by Trump in the past. Throughout the course of the pandemic, Trump downplayed the risks of COVID-19, justifying his actions by claiming that he didn’t want to create panic. On top of this, Trump spent years casting doubt on childhood vaccines before he became president, asserting that they caused autism despite receiving strong scientific pushback.

But partisan division isn’t the only impetus behind vaccine hesitancy amongst Americans. 57% of those unwilling to take the vaccine cite fear of the possible side effects as their primary reason for not taking the vaccine. This reasoning seems to be one of the driving factors behind the slow vaccination rollouts, as many with priority access to vaccines are refusing to get them.

In California, a state leading the nation in cases and second in deaths, frontline workers in heavily impacted counties like Los Angeles and Riverside are refusing the vaccine in large numbers. Somewhere between 20 and 40% of Los Angeles health workers declined the vaccine. About 50% of Riverside health workers did the same. Overall, the Kaiser Family Foundation reports that around 29% of healthcare workers are vaccine hesitant. Healthcare workers are not the only ones to have refused the vaccine with priority access, though. Approximately 25% of California nursing home staffers are also refusing the vaccine, despite the fact that nursing homes account for approximately 35% of COVID-19 deaths in the state.

Sadly, simply vaccinating more willing groups first may prove more difficult than it seems.

Online servers indicate that having priority access may be the cause of some of these workers’ reluctance to take the vaccine, as many associate it with experimentation. Additionally, some health care workers feel uncertainty as they, too, must contend with widespread misinformation campaigns sowing doubt in the vaccine.

Sadly, simply vaccinating more willing groups first may prove more difficult than it seems. In spite of the fact that support for the vaccine is historically high, as many as 62% of Americans say they would be uncomfortable forming part of the first group of vaccine recipients. This mirrors the sentiment of 53% of vaccine-hesitant Americans who say the vaccine is too new and they want to see how it works for other people.

Part of the trouble seems to be that the lack of a unified message surrounding the vaccine has caused mistrust throughout the American public. Leading government organizations providing vaccine information, such as the Centers for Disease Control and Prevention, or CDC, and the FDA, currently experience wide gaps in trust across both partisan and racial/ethnic splits.

For example, the CDC is trusted by 88% of Democrats but just 57% of Republicans. This divide in trust deepens even further when politicians serve as sources of information on the COVID-19 vaccine, swinging as much as 71% in some instances across party lines and 29% across racial lines. By far, respondents to a survey by the Kaiser Family Foundation ranked personal doctors or health providers as their most trusted source of information on the COVID-19 vaccine across both political and racial/ethnic divides with 85% overall trust.

In order to safely return to normal life, Americans must make gains in vaccine willingness across all demographics. Ideally, the nation could accomplish this goal through unified messaging from politicians and government organizations alike. However, a more realistic solution may be something closer to a concerted effort to combat misinformation and vaccine hesitancy among health care workers themselves, helping instill trust in the general public. After everything, it would be a shame to make a preventable trip over the final hurdle of vaccination.