A milestone was reached Friday in the battle against COVID-19. The United States became the first nation in the world to pass 100 million vaccinations.

At least 100M people have received at least one shot of the vaccine. Another 56 million people, 17% of the U.S. population, has now been fully vaccinated. In all, about 40% of American adults are at least partially vaccinated. As that news was released, the White House touted President Biden’s aggressive vaccination program.

The news comes at a time when the nation is at a bit of a crossroads in the COVID fight. The CDC issued new guidance giving the all-clear for fully-vaccinated people to travel again.

But some experts fear that “pandemic fatigue” may lead to people letting their guard down and sparking new wave of outbreaks. And the numbers indicate their concerns are well-founded.

The U.S. is averaging 64,000 cases per day this week, up from a daily average of 55,000 infections just two weeks ago. Deaths have remained steady at around 900 a day. With MLB opening their season up this week, there’s concern the ballparks could become superspreader locations. The Washington Nationals canceled a home game Thursday due to a player testing positive for coronavirus.