The spread of the omicron subvariant BA.2 in the United States may be slowing down, a study finds older Covid-19 survivors experience cognitive impairment even a year later, and more in this week's roundup of Covid-19 news.

• Pfizer on Wednesday announced that it will begin phase II/III testing of its Covid-19 antiviral pill, Paxlovid, in children. FDA first authorized Paxlovid in December to treat Covid-19 in high-risk individuals ages 12 and older who weigh at least 88 pounds. According to the Politico, the upcoming phase II/III trials will include around 140 children ages 6 to 17, who will be divided into two groups. The first group will include participants who weigh at least 88 pounds. They will receive the dose of Paxlovid currently authorized for individuals ages 12 and up. The second group will include participants between 44 and less than 88 pounds, who will receive a smaller dose of the drug. Both groups will receive one dose twice a day for five days, or 10 doses in total. "We are proud to expand studies of our novel Covid-19 treatment to include pediatric participants to further evaluate the safety and efficacy of this treatment in this important population," said Mikael Dolsten, Pfizer's chief scientific officer and president of worldwide research, development, and medical. Pfizer expects results from these trials to be available by the end of the year, according to Annaliesa Anderson, who leads the company's Paxlovid research. (Foley, Politico, 3/9; Hopkins, Wall Street Journal, 3/9)

• According to a study from Japan, the omicron variant is at least 40% more deadly than the seasonal flu. The study, which has not been peer reviewed or published, analyzed omicron's case-fatality since January in Japan and compared it to both earlier case-fatality rates during the pandemic and from the seasonal flu. Overall, researchers found that omicron's case-fatality rate was around 0.13%, much lower than the 4.25% rate from earlier in the pandemic but higher than the 0.006% to 0.09% seen with the seasonal flu. "[T]here's a considerable difference in mortality [between the coronavirus and the seasonal flu]," said Takaji Wakita, chair of the Japanese health ministry's advisory board, though he noted that omicron has helped close the gap between the two viruses. More research is also needed to determine how lifting pandemic restrictions will impact Covid-19 case-fatality rates, Wakita said. (Matsuyama, Bloomberg, 3/2)

• The spread of the omicron subvariant BA.2, also known as "stealth omicron," appears to be slowing in the United States, according to new CDC data. Since mid-February, the subvariant's prevalence among U.S. Covid-19 cases had been doubling every week, going from 4.4% the week ending Feb. 19 to 8.3% the week ending Feb. 26. However, this trend may be ending, although its prevalence is still rising. For the week ending March 5, the prevalence of the BA.2 subvariant was 11.6%. Overall, there have been 4,690 confirmed Covid-19 cases attributed to the BA.2 subvariant as of March 8. According to Michael Osterholm, an epidemiologist and the director of the Center for Infectious Disease Research and Policy at the University of Minnesota, it's unclear whether the subvariant will potentially lead to another major surge in Covid-19 cases. (Bean, Becker's Hospital Review, 3/9)

• The World Health Organization's (WHO) advisory group on Covid-19 vaccines on Tuesday said it endorsed widespread use of and access to booster doses. Previously, WHO Director-General Tedros Adhanom Ghebreyesus last year called for a moratorium on booster doses for the general public, saying that wealthy countries should instead donate the doses to poor countries where vaccine access remains limited. However, the advisory group in January said that evidence "supporting the need for [a] booster, particularly for the highest risk groups, has become increasingly clear over the past few months." In a statement, WHO said it "strongly supports urgent and broad access to current Covid-19 vaccines for primary series and booster doses, particularly for groups at risk of developing severe disease." (Doherty, Axios, 3/8; AP/Modern Healthcare, 3/8; Astor, New York Times, 3/8)

• FDA last week rejected Ocugen's application for emergency use authorization of its Covid-19 vaccine for individuals ages 2-18. The vaccine, which is made by the India-based pharmaceutical company Bharat Biotech, has been authorized by around 20 countries and WHO. The vaccine has not been tested in the United States, but a clinical trial from India of participants ages 2-18 found that two doses of the vaccine generated strong immune responses and did not have serious side effects. Ken Inchausti, an Ocugen spokesperson, said the company was "disappointed" by FDA's decision but that it still wants to find a way to authorize the vaccine for 2-to-18-year-olds in the United States. According to the New York Times, Ocugen will continue to seek full FDA approval of its Covid-19 in adults and plans to begin enrolling adult participants in the United States in a clinical trial to evaluate the vaccine's immune response. (Robbins, New York Times, 3/4)

• Older adults who were hospitalized with Covid-19 continued to experience cognitive impairment a year later, according to a new study published in JAMA Neurology. For the study, researchers examined 1,438 Covid-19 survivors ages 60 and older who were discharged from three hospitals in Wuhan, China, between Feb. 10 and April 10, 2020. Patients received follow-up monitoring of their cognitive function at six and 12 months after hospital discharge. Overall, the researchers found that 12.45% reported cognitive impairment 12 months later. Approximately 3% of patients had incident dementia, and 9.1% had mild cognitive decline. Patients with severe Covid-19 were also more likely to experience dementia and mild cognitive impairment at 15% and 26.15%, respectively. According to the researchers, the study's findings "imply that the pandemic may substantially contribute to the world dementia burden in the future." (George, MedPage Today, 3/8)