Unvaccinated US tourists are no longer welcome in Denmark or The Netherlands.
The countries announced the new vaccination requirements days after the European Union took the country off its safe travel list earlier in the week over the surge in COVID-19 cases, according to USA Today.
The move led other EU countries to respond with new restrictions on American visitors.
In addition to banning unvaccinated Americans, The Netherlands will also require US travelers who have had their shots to self isolate, officials said.
Bulgaria will now completely ban travel from the states, and Italy imposed testing and quarantine requirements on US tourists, the article said.
The US has yet to welcome most European tourists to the country, according to the CDC.
There have been an average of 1,114 daily deaths across the 50 states over the past week, and more than 150,000 new daily cases, federal health officials reported Saturday.
Only 53 percent of the US population is fully vaccinated, compared to about 70 percent of people in the EU, officials said.