Psaki said she has mild symptoms and is working from home.
As the COVID-19 pandemic has swept the globe, more than 4.9 million people have died from the disease worldwide, including over 744,000 Americans, according to real-time data compiled by Johns Hopkins University's Center for Systems Science and Engineering.
Just 67.7% of Americans ages 12 and up are fully vaccinated against COVID-19, according to data from the U.S. Centers for Disease Control and Prevention.
The European Medicines Agency on Monday approved the Moderna booster (which is a half dose of the initial booster) for people 18 and older.
The booster "given 6 to 8 months after the second dose led to a rise in antibody levels in adults whose antibody levels were waning," the EMA said.
-ABC News' Christine Theodorou
The federal government on Monday released more details about how foreign tourists and other non-citizen, non-immigrant people flying to the U.S. can comply with recently-announced rules requiring them to be fully vaccinated.
These rules go into effect on Nov. 8.
People will be able to submit proof of vaccination to airlines electronically or via paper, an official said.
All vaccinated people -- Americans and non-Americans -- need to show proof of a negative test taken within three days before departure.
For unvaccinated people -- both Americans and non-Americans -- you need to show proof of a negative test within one day before. Children ages 2 to 17 must take a test but those under 2 don’t need to test.
Vaccine exemptions include: children under 18; some medical exemptions; and people traveling on non-tourist visas from countries with low availability of vaccines (signified by a country having a vaccination rate less than 10%). The U.S. will follow a list maintained by the WHO and these people will need have a “specific, compelling reason” for coming to the U.S., a senior administration official said.
The exemptions will represent a “very, very small number” of travelers to the U.S., a senior administration official said.
-ABC News' Ben Gittleson
In the last month, the daily case average in the U.S. has dropped by nearly 43% thanks to falling metrics in states like Florida, Mississippi and Louisiana, which have all seen their case averages drop by nearly 90% or more since August, according to federal data.
But in recent weeks, cases have been creeping up in several states in the Northeast and the upper Midwest, including Minnesota and Michigan.
Alaska currently has the country's highest infection rate, followed by Montana, Wyoming, Idaho and North Dakota, according to federal data.
About 52,000 COVID-19 patients are currently hospitalized across the U.S., a major drop from the 104,000 hospitalized patients in late August.
But the U.S. death toll remains persistently high, with nearly 1,300 new deaths being reported each day, according to federal data.
-ABC News' Arielle Mitropoulos
Moderna has announced that its vaccine produces a strong immune response for children 6 to 11 and appears safe.
The study, which included 4,753 kids, found that side effects were generally consistent with those seen in adolescents and adults, such as fatigue, headache, fever and sore arm.
Moderna said it plans to submit this data to the FDA soon.
Meanwhile, FDA advisors are planning to meet this week to discuss Pfizer's vaccine for children ages 5 to 11. Full authorization is possible by early November.
-ABC News' Sony Salzman
