The U.S. is likely reaching the end of the road on new vaccinations, after the U.S. Supreme Court blocked the Biden administration's vaccine mandate for large employers.

Why it matters: Cash prizes and other incentives barely moved the needle on vaccinations. So the government turned from carrots to sticks — but now it has lost its biggest stick.

• "It is now highly unlikely that the U.S. will hit the ~85-90% of Americans vaccinated to get to the other side of the pandemic," tweeted Celine Gounder, an infectious disease expert and former Biden administration advisory board member.

By the numbers: 63% of eligible Americans are fully vaccinated and about 38% of them have gotten boosted.

• About 75% of Americans have gotten at least one dose of a COVID vaccine, according to the CDC.

State of play: Employers in most of the country are still free to impose their own mandates, if they want to, but there's not much reason to expect that to produce any major increase in vaccinations.

• Only a few large companies, such as United Airlines, have required vaccines. Most employers haven't enacted a mandate, and labor shortages could make them even less likely to do so now.
• Plus, 13 states prohibit employers from enacting vaccine mandates, according to data from KFF.

Between the lines: Early on in the pandemic, many companies tried to entice employees to get shots using cash incentives or paid days off, but found limited success.

• "Mandates appear to be the only way to get to that high a vaccination level, you cannot do it with education or nudges," Jeff Levin-Scherz, a population health leader at Willis Towers Watson, told Axios.

Yes, but: The Supreme Court allowed the federal vaccine mandates for health care facilities to take effect.

• That does, however, raise serious concerns about workforce shortages that could unevenly hit health systems in regions with low vaccination rates, in rural areas where workforces are already much smaller, or among certain job categories where there are alternative jobs paying comparable wages.

What to watch: The court left the door open for narrower regulations, targeted to specific types of workplaces.

• "Likely candidates for regulation include workplaces where social distancing is difficult, such as manufacturing lines, or where mask-wearing is impossible, such as restaurants," Aaron Goldstein, a partner in the firm of Dorsey & Whitney, said in an email.