World Health Organization announces coronavirus variants will now be named after Greek letters, a new coronavirus variant is discovered in Vietnam, and more.

• The World Health Organization (WHO) on Monday announced variants of the coronavirus will now be named after letters of the Greek alphabet, to simplify the variants' names and avoid names that can be stigmatizing to a country. According to the new naming system, the variant B.1.1.7, which was first discovered in the United Kingdom, will now be called Alpha; the B.1.351 variant first discovered in South Africa will be called Beta; and the B.1.617.2 variant first discovered in India will be called Delta. Once all 24 letters of the Greek alphabet have been used, WHO said it will announce another naming system (Weise, USA Today, 6/1; Davies, Bloomberg, 6/1; Branswell, STAT News, 5/31).

• CDC on May 17 updated its testing guidance saying vaccinated people can forgo Covid-19 testing in most situations, including exposure to someone who tested positive for the coronavirus. However, fully vaccinated people should still get tested if they're experiencing Covid-19 symptoms, CDC said. While fully vaccinated people can potentially develop Covid-19, they're at a small risk of developing a serious case of the disease, the Associated Press reports, and some experts say the cost of getting a Covid-19 test outweighs the benefits for vaccinated people. "At this point, we really should be asking ourselves whether the benefits of testing outweigh the costs—which are a lot of disruptions, lots of confusion, and very little clinical or public health benefit," A. David Paltiel, from Yale University's School of Public Health, said (Bean, Becker's Hospital Review, 5/24; Perrone, Associated Press, 5/23).

• Although children who develop Multisystem Inflammatory Syndrome in Children (MIS-C), a rare Covid-related inflammatory syndrome, may be able to fight off their most serious symptoms within six months, they may still have weakness in their muscles and emotional difficulties, according to a new study in The Lancet Child and Adolescent Health. For the study, researchers looked at the health status of 46 children hospitalized for MIS-C between April 4 and Sept. 1, 2020. Six months after the children were discharged, the researchers found that just one still had systemic inflammation, two had heart abnormalities, and six had gastrointestinal symptoms; no children had passed away. However, 18 children were still experiencing muscle weakness and fatigue, and 15 were experiencing emotional difficulties, such as anxiety or severe mood swings (Belluck, New York Times, 5/24; Christensen, CNN, 5/25).

• Certain Covid-19 mitigation measures, such as masking requirements, improved ventilation, and frequent surveillance testing, could help schools keep Covid-19 cases down, according to two new studies. One of the studies, published in CDC's Morbidity and Mortality Weekly Report, looked at 169 elementary schools in Georgia that offered in-person education in the fall of 2020. Researchers found that the presence of the coronavirus was 35% lower at schools with improved ventilation than those without, and 48% lower in schools that combined improved ventilation with the use of HEPA air filters. In addition, the presence of the coronavirus was 37% lower in schools that required adults to wear masks. Meanwhile, a second study from researchers at the Utah Department of Health and the University of Utah, found that between Jan. 4 and March 20, 2021, 28 high schools saw sizable Covid-19 outbreaks. Of those 28 schools, 15 moved to remote learning and 13 conducted surveillance testing. Of the more than 13,000 students tested, just 0.7% tested positive, and all 13 schools were able to remain open (Anthes, New York Times, 5/21; Turner, NPR, 5/21; Coleman, The Hill, 5/21).

• The Vietnamese Health Ministry on Saturday announced that a new variant of the coronavirus has been discovered and is believed to have caused a recent surge in Covid-19 infections in the country. According to Health Minister Nguyen Thanh Long, the new variant is a mixture of the variant first discovered in India with mutations belonging to the variant first discovered in the United Kingdom (Vella, The Hill, 5/29).

• NIH on Tuesday announced it has started an early-stage clinical trial looking at the immune responses in fully vaccinated adults after they receive booster shots of a different brand of Covid-19 vaccine than the one they initially received. The study will look at the safety of mixing vaccines and the efficacy of the booster shots against emerging coronavirus variants, NIH said. The study will include 150 participants who have received one of the three Covid-19 vaccines authorized for use in the United States (Lovelace, CNBC, 6/1; Falconer, Axios, 6/2; Loftus, Wall Street Journal, 6/1).

• Francis Collins, director of NIH, on Tuesday published a blog post saying that two recent studies of both Pfizer and Moderna's Covid-19 vaccines show the vaccines are "completely safe" and effective for pregnant people. According to Collins, the studies found both vaccines produced the levels of antibodies and immune cells necessary to protect against Covid-19. The vaccines were also likely to provide protection to infants as well as the vaccinated person, Collins said (Kindelan, ABC News, 6/1).