The U.S. Centers for Disease Control and Prevention has upped its travel warning for Singapore to the highest tier, Level 4, urging travelers to avoid visiting the city-state.

Singapore last week announced it would open its Vaccinated Travel Lanes program to several new countries, including the United States, this week, enabling fully vaccinated travelers to visit without quarantine if they follow testing protocols. While Singapore reports a vaccination rate about 82 percent, it has seen a spike in Covid-19 cases in recent weeks, leading the CDC to warn of a “very high” level of Covid-19 in Singapore and a risk for even fully vaccinated travelers to catch and spread Covid-19 variants.

Singapore was the only new country added to the CDC’s Level 4 warning in its most recent update. Three countries were moved down to Level 3 from Level 4—Cyprus, Eswatini and Tunisia—and three were moved up to Level 3 from Level 2: Angola, Djibouti and Hungary.

Bangladesh, Bolivia, Cameroon, Ghana, Kenya, Poland and the Republic of the Congo all moved to Level 2 in the update, and Bhutan, Paraguay, Senegal and Zambia all moved to Level 1.