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The Pfizer-BioNTech Covid-19 vaccine loses some potency against the coronavirus variant that first appeared in South Africa, researchers reported Wednesday, based on lab experiments. What the findings mean for how well the vaccine will protect real people from the variant, called B.1.351, is hard to tell. But clinical data from three other vaccines — those from AstraZeneca, Novavax, and Johnson & Johnson — have already shown the shots are not as powerful at blocking symptomatic Covid-19 cases caused by B.1.351 as by other forms of the virus. (Joseph, 2/17)

All of the blood samples from vaccinated patients still showed significant levels of neutralizing antibody against the South Africa variant, the researchers said. The study was conducted by Pfizer, BioNTech and researchers at the University of Texas Medical Branch at Galveston and published in the New England Journal of Medicine. ... What the lab data means in practice remains to be seen. “It is unclear what effect a reduction in neutralization by approximately two-thirds would have” on protection from Covid-19 caused by the South Africa variant, the Pfizer study concluded. (Kresge and Langreth, 2/17)

Because there is no established benchmark yet to determine what level of antibodies are needed to protect against the virus, it is unclear whether that two-thirds reduction will render the vaccine ineffective against the variant spreading around the world. However, UTMB professor and study co-author Pei-Yong Shi said he believes the Pfizer vaccine will likely be protective against the variant. “We don’t know what the minimum neutralizing number is. We don’t have that cutoff line,” he said, adding that he suspects the immune response observed is likely to be significantly above where it needs to be to provide protection. (Erman, 2/17)

Covid-19 variants are threatening to cause another surge of infections, health officials warned Wednesday, and it's now more important than ever for Americans to continue practicing safety measures that work against the spread of the virus. (Maxouris, 2/18)