The World Health Organization authorizes the coronavirus vaccine developed by AstraZeneca, the United Kingdom approves a human challenge trial in which volunteers will be infected with the new coronavirus, and more.

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• New research in the New England Journal of Medicine finds that the coronavirus vaccines developed by Pfizer and BioNTech appear to be highly effective against the B.1.1.7 coronavirus variant—first discovered in Britain—but do not appear as robustly effective against the B.1.351 variant, which was first discovered in South Africa. For the study, researchers compared blood samples from 15 people who had received Pfizer/BioNTech's vaccine and found that, against a version of the virus genetically altered to have mutations found in the B.1.351 variant, the immune system had two-thirds less neutralization power compared with other forms of the new coronavirus, but it was still able to neutralize the virus. Scott Weaver, director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch and study author, said, "Although we do not yet know exactly what level of neutralization is required for protection against Covid-19 disease or infection, our experience with other vaccines tells us that it is likely that the Pfizer vaccine offers relatively good protection against [B.1.351]" (Joseph, STAT News, 2/17; Cunningham et al., Washington Post, 2/18; Sealy/Bonifield, CNN, 2/17).

• The United Kingdom has approved a study in which a small group of unvaccinated volunteers will be deliberately infected with small droplets of the new coronavirus in order to gain insights about the immune system's response to the virus. Since researchers will be able to control how much of the virus the participants are exposed to, they hope to learn more about how the immune system responds and develop methods for comparing how effective different treatments and vaccines are (Adam, Washington Post, 2/17; Mueller, New York Times, 2/17).

• The World Health Organization (WHO) on Monday authorized AstraZeneca's coronavirus vaccine, allowing partners of the agency to ship doses to lower- and middle-income countries, as part of WHO's COVAX initiative, which aims to facilitate equitable vaccine distribution. According to Mariângela Simão, assistant director general for access to medicine and health products for WHO, the authorization means that "[c]ountries with no access to vaccines to date will finally be able to start vaccinating their health workers and populations at risk." Meanwhile, AstraZeneca announced that it intends to double its per-month vaccine output to 200 million doses by April. The drugmaker also announced it was aiming to reach production for an adapted vaccine for variants of the novel coronavirus within six to nine months (Mueller, New York Times, 2/15; Cheng, AP/Washington Post, 2/15; Coleman, The Hill, 2/11; Strasburg, Wall Street Journal, 2/11).

• WHO on Friday also announced that preliminary findings suggest that patients who have recovered from Covid-19 have been infected again with the B.1.351 coronavirus variant. Relatedly, Soumya Swaminathan, WHO's chief scientist, noted that vaccines against the novel coronavirus, while not able to shield people completely from infection, do appear to reduce the severity of Covid-19 in those who develop the disease. Swaminathan added that coronavirus vaccines may also decrease spread of variants of the virus. "There are reports now that if you have the vaccine and you get infected, the viral load is much lower," she said. "So the chances of infecting others may be lower" (Miao, CNBC, 2/12).

• Researchers at the Yale School of Medicine have published a study suggesting a particular kind of saliva test, when compared with nasal swabs, may more accurately determine who among those infected with the novel coronavirus will develop severe Covid-19. According to the researchers, the test can determine whether a patient's saliva contains high levels of the coronavirus, which indicates the virus likely has moved to the patient's lungs, where it is most dangerous. Currently, the saliva test examined in the study can be performed only in authorized labs, but the researchers said it may become more widely available if studies prove its efficacy and FDA approves it (Nather, "Vitals," Axios, 2/17).