In an update, the agency instructed people to "avoid travel to Canada," adding that if people "must" travel there they should make sure they are fully vaccinated prior to doing so.
"Because of the current situation in Canada, even fully vaccinated travelers may be at risk for getting and spreading COVID-19 variants," the CDC said.
It also advised travelers to follow recommendations or requirements in Canada, including wearing a mask and socially distancing.
"Do not travel internationally until you are fully vaccinated. Getting vaccinated is still the best way to protect yourself from severe disease, slow the spread of COVID-19, and reduce the number of new variants. CDC encourages you get a COVID-19 vaccine booster dose if you are eligible. People who are not fully vaccinated should follow additional recommendations before, during, and after travel," the CDC noted.
In its own post, the U.S. Department of State Bureau of Consular Affairs wrote a similar message.
"The Centers for Disease Control and Prevention (CDC) has issued a Level 4 Travel Health Notice due to COVID-19, indicating a very high level of COVID-19 in the country. Your risk of contracting COVID-19 and developing severe symptoms may be lower if you are fully vaccinated with an FDA authorized vaccine. Before planning any international travel, please review the CDC's specific recommendations for vaccinated and unvaccinated travelers," it said.
According to U.S. Embassy and Consulates in Canada, all travelers in the country must be fully vaccinated in order to travel by most air, rail or passenger vessels.
"In addition, some provinces continue to limit discretionary activities, such as visits to restaurants, bars, gyms and retail shops, to individuals who can provide proof of COVID-19 vaccination," the embassy pointed out.
The Johns Hopkins Coronavirus Resource Center shows Canada reported 29,266 cases in the past day with 93 deaths.
Since the beginning of the pandemic, the nation has reported more than 2.6 million confirmed cases and more than 31,000 deaths.