As of Jan. 23, all non-US citizens, including permanent residents, entering the US via land or ferry are now required to show proof of completed COVID-19 vaccination. At press time, the US did not require a booster shot in order to be considered fully vaccinated.
While US citizens are exempt from the vaccination requirement, anyone crossing the border, including US citizens, must present a negative COVID test taken within the last 24 hours, regardless of vaccination status.