[ti:US: COVID Shots for Autumn Must Target Omicron] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]The U.S. Food and Drug Administration, or FDA, [00:04.84]says COVID-19 booster shots for autumn [00:08.28]will have to add protection against the latest Omicron sub-variants. [00:15.28]Two widely used COVID-19 shots made by Moderna and Pfizer-BioNTech [00:21.72]have saved millions of lives worldwide in just their first year of use. [00:29.44]The FDA said they would be used for anyone still getting their first shots. [00:37.00]But with immunity waning and the super-contagious Omicron family of variants [00:42.76]getting better at escaping antibodies protection, [00:46.48]the boosters will need an update. [00:50.60]Waning immunity means that the effectiveness of the vaccine decreases over time. [00:58.92]Antibodies are the first layer of defense [01:02.28]that form after vaccination or an infection. [01:07.04]They can prevent infection by recognizing the outer coating [01:11.64]of the new coronavirus -- the spike protein [01:15.00]-- and blocking it from entering your cells. [01:19.40]Separate studies published recently in Nature [01:23.16]and the New England Journal of Medicine [01:25.56]show the newest sub-variants of Omicron [01:28.80]are even better at avoiding antibodies. [01:33.60]The studies showed this happened both in the vaccinated [01:37.48]and in people who recovered from the original Omicron variant. [01:43.20]Drug companies Moderna and Pfizer [01:46.08]said they were already working [01:48.36]on booster shots that add protection against Omicron. [01:54.20]The new combination shots, called "bivalent" by scientists, [01:59.44]showed increased levels of antibodies [02:02.56]against the original Omicron variant. [02:06.72]But they did not provide nearly as many antibodies [02:10.68]against its two sub-variants, known as BA.4 and BA.5. [02:18.68]Scientists support the "bivalent" shot because it combines [02:23.48]the original vaccines' proven benefits [02:26.64]with new protection against other variants. [02:31.32]The Centers for Disease Control and Prevention (CDC) [02:34.80]said the two worrisome sub-variants [02:37.68]now make up half of all infections in the U.S. [02:43.32]Both Moderna and Pfizer said [02:46.16]they will have combination shots to deal with Omicron by October. [02:52.56]A Pfizer spokeswoman told the Associated Press in an email: [02:57.08]"We're continuing to collect more data from our study on BA.4/5 [03:03.12]and will be in touch as soon as we are ready to submit." [03:08.40]But Moderna said changing the shots to target the sub-variants [03:13.00]might delay its version another month. [03:17.84]A third company, Novavax, is awaiting FDA authorization [03:23.32]for its more traditional, protein-based COVID-19 vaccine. [03:29.40]Novavax argued that a booster of its regular vaccine [03:34.24]promises higher immunity against the Omicron variant. [03:39.80]"None of us has a crystal ball" to know the next threatening variant, [03:44.60]said FDA vaccine chief Dr. Peter Marks last week. [03:50.40]The expression having a crystal ball [03:53.16]means having the ability to predict the future. [03:57.96]Marks added that the agency will try [04:00.96]to "bring the immune system closer" [04:03.32]to the new variants rather than the older ones. [04:07.80]"We would obviously like to get it right enough [04:11.16]so that with one more shot we get a full season of protection," he said. [04:17.64]The FDA's order does not guarantee that [04:21.32]those combination shots would be offered in autumn. [04:26.24]Drug makers still must provide data from human trials [04:30.92]before the agency decides whether to authorize the modified boosters. [04:37.84]Then, the CDC would have to decide how they are used. [04:43.68]It is not clear who would be offered a new combination booster shot. [04:49.36]They might be urged only for older adults [04:53.04]or those at high risk from the virus. [04:57.44]Advisers to the World Health Organization (WHO) [05:00.56]recently said Omicron-targeted shots would be most useful as a booster [05:06.24]because they should increase cross-protection against several variants. [05:12.68]Dr. Kanta Subbarao is a virologist who heads the WHO committee. [05:19.56]"We don't want the world to lose confidence in vaccines [05:23.84]that are currently available," she said. [05:27.72]I'm Jonathan Evans. 更多听力请访问51VOA.COM