Unprotected American tourists are no longer welcome in Denmark or the Netherlands.
Countries announced new vaccination requirements days after the European Union removed the country from its safe travel list earlier in the week due to an increase in COVID-19 cases, according to USA Today.
The move prompted other European Union countries to respond by imposing new restrictions on US visitors.
In addition to banning unvaccinated Americans, the Netherlands will also require American travelers who have received their vaccines to self-isolate, officials said.
The article said Bulgaria will now completely ban travel from the states and Italy has imposed testing and quarantine requirements on US tourists.
According to the Centers for Disease Control and Prevention, the United States has not yet received most European tourists into the country.
Federal health officials reported Saturday that there have been an average of 1,114 daily deaths in all 50 states and more than 150,000 new daily cases in the past week.
Officials said only 53 percent of the US population has been fully vaccinated, compared to about 70 percent of people in the European Union.
