In the coming months, America could reach a point when it has more Covid-19 vaccines than people want.

Between efforts from the federal government and drug companies to step up manufacturing and distribution, the US’s vaccine supply is truly increasing: At least 150 million doses are expected through March — a rate of more than 3 million shots a day, the kind of speed the country needs to reach herd immunity, when enough people are protected against the virus to stop its spread, this summer.

But public health experts are increasingly warning of what may come as America inches closer to the finish line in its vaccine campaign: After the majority of people who want a vaccine get one, there’s a large minority of people who have voiced skepticism in public surveys. And if these people don’t change their minds in the coming months, they could doom any chance the US has of reaching herd immunity.

“There’s going to be a point … where there’s going to be vaccine available, and getting people to take it will be the primary issue,” Emily Brunson, a medical anthropologist at Texas State University, told me.

To reach herd immunity, experts generally estimate that we’ll need to vaccinate at least 70 to 80 percent of the population — though it could be more or less, because we don’t really know for sure with a new virus. Yet according to a recent AP-NORC survey, 32 percent of Americans say they definitely or probably won’t get a Covid-19 vaccine. If that holds and the herd immunity estimates are correct, it would make herd immunity impossible.

Public health experts say there are ways to make people more willing to get vaccinated, but such efforts have to be flexible to match the different concerns about a vaccine different communities and individuals may hold. What might sway skeptical white Republicans who don’t see Covid-19 as a threat won’t necessarily work for Black communities that are distrustful of a medical establishment that has long neglected and even abused them.

Whatever anti-hesitancy campaigns take shape, though, must happen quickly. With every day the coronavirus continues to spread across America, the country sets itself up for hundreds if not thousands more deaths a day — not to mention the constant need for social distancing, a weakened economy, and potentially harsher restrictions on daily life. Each day of uncontrolled spread also brings the risk of new, more dangerous coronavirus variants, as each replication of the virus carries the risk of a mutation that catches on more widely.

Now, the days when hesitancy becomes the top vaccine problem may still be up to months away. But if the pandemic should have taught us anything, it’s that it’s better to be proactive than reactive. It’s not too late to get ahead of this problem before it becomes the next major bottleneck in America’s efforts to end its outbreak.