FDA asks Moderna and Pfizer-BioNTech to expand their clinical trials for children under 12, CDC plans to withdraw emergency use authorization of one of the earliest real-time Covid-19 tests, and more in this week's roundup of Covid-19 news.

• CDC last week announced it would withdraw its emergency use authorization request for one of the earliest real-time Covid-19 tests, the CDC 2019-Novel coronavirus Real-time PCR Diagnostic Panel, from FDA after December 31. In the notice, CDC said it was providing advance notice to clinical laboratories so they would have enough time to select and use alternative FDA-approved diagnostic tests. In addition, CDC encouraged labs to considering using dual tests that would be able to detect both the coronavirus and influenza virus, which the agency said "can save both time and resources as we head into influenza season." (Carbajal, Becker's Hospital Review, 7/26)

• People who received a dose of AstraZeneca's Covid-19 vaccine and then a dose of Pfizer-BioNTech's Covid-19 vaccine developed around six times more neutralizing antibodies compared to those who received two AstraZeneca doses, according to a new study from South Korea. For the study, researchers assessed 499 medical workers, with 100 participants receiving one dose of each vaccine, 200 receiving two doses of the Pfizer-BioNTech vaccine, and the remainder receiving two doses of the AstraZeneca vaccines. According to Reuters, the mixed vaccine regimen resulted in a similar antibody levels as two doses of the Pfizer-BioNTech vaccines. These results provide further support to a British study published last month showing similar information, The Hill reports. (Oshin, The Hill, 7/26; Cha, Reuters, 7/26)

• Coronavirus cases in the country could quadruple in the next four to six weeks due to the spread of the highly contagious delta variant, according to former CDC Director Tom Frieden. "We're heading into a rough time. It's likely, if our trajectory is similar to that in the United Kingdom, that we could see as many as 200,000 cases a day," Frieden said on Monday. He added that although the United States would not be likely to see the "horrific death tolls" it saw earlier in the pandemic—since many of those who are most vulnerable have been fully vaccinated—there will be "a steady increase in … preventable deaths." According to data from Johns Hopkins University, the U.S. averaged 57,300 new cases over the last week, and the last time the U.S. reported more than 200,000 cases in a day was in January. (Lonas, The Hill, 7/27; Holcombe/Almasy, CNN, 7/28)

• Pfizer and BioNTech last week announced they will partner with the Biovac Institute, a biopharmaceutical company in South Africa, to manufacture Covid-19 vaccines for exclusive distribution in the African Union. Under the agreement, Biovac will fill vials with the prepared Pfizer-BioNTech vaccine and ready it for shipment. Production is set to begin in 2022, and the companies said Biovac's facility will produce more than 100 million vaccine doses a year once it is fully operational. According to Axios, currently just 3% of people in Africa have received at least one dose of a Covid-19, and new coronavirus cases throughout the continent have doubled every three weeks amid the spread of the delta variant. (Chen, Axios, 7/21; Wexler/Hopkins, Wall Street Journal, 7/21)

• Moderna and Pfizer-BioNTech are expanding the number of children ages 5 to 11 included in their vaccine clinical trials after FDA indicated that the current size and scope of their studies were not large enough to detect rare side effects, the New York Times reports. According to individuals familiar with both trials, these side effects include myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining around the heart). FDA asked the companies to expand their trials to include 3,000 children between 5 and 11 years old. A federal official, who spoke anonymously to the Washington Post, said the government does not expect there to be problems enrolling more children in the studies and that authorization of a Covid-19 vaccine for children ages 5 through 11 is expected between late October or early November. (Stolberg et al., New York Times, 7/26; McGinley et al., Washington Post, 7/26)