Just two months have passed since the U.S. Centers for Disease Control and Prevention relaxed its guidelines on mask wearing.
But, the CDC on Tuesday changed its stance, and recommended that even those vaccinated should wear masks indoors.
This comes as the U.S. has seen more than 57-thousand cases of COVID-19 a day on average, over the past week, mainly due to the impact of the Delta variant.
"Information on the Delta variant from several states and other countries indicates that in rare occasions, some vaccinated people infected with the Delta variant after vaccination may be contagious and spread the virus to others. This new science is worrisome and unfortunately warrants and update to our recommendation."
The CDC also recommended all students and teachers at schools to wear masks for the upcoming Fall semester, regardless of their vaccination status.
The Delta variant is also spreading quickly in Japan, as Tokyo alone confirmed 3-thousand 1-hundred 77 new cases on Wednesday, the highest number since the start of the pandemic.
The number of cases on Wednesday beat the city's previous record set on Tuesday of 2,848.
The surrounding prefectures of Saitama, Chiba and Kanagawa, have also accounted for a big proportion of the country's total cases.
A top Japanese government official on Wednesday said the government is working closely with Tokyo's neighboring prefectures to issue a state of emergency if requests are made.
"We will keep cooperating, and in case we receive a request from the neighboring prefectures, we will take it into consideration immediately and make judgments on issuing a state of emergency in accordance with our basic policy."
In regards to whether the Olympics should be called off, though, Japanese Prime Minister Yoshihide Suga said there was no need to worry as fewer people are moving around and most are working remotely.
Shin Ye-eun, Arirang News.