The first and second doses of the Pfizer-BioNTech vaccine are approved to be delivered within a 21-day window, while the Moderna injections should be spread over 28 days. When given at those intervals, both vaccines are about 95% effective, according to the respective drugmakers. But the FDA has heard suggestions that the number of limited doses could be stretched by cutting them in half, extending the length of time between doses, or mixing and matching vaccines in order to immunize more people against COVID-19.
NPR： FDA Warns Health Officials Not To Mess With COVID-19 Vaccine Doses Schedule
The U.S. Food and Drug Administration is warning health care workers that any changes to the authorized dosing schedules of COVID-19 vaccines currently being administered significantly place public health at risk and undermine "the historic vaccination effort to protect the population" from the coronavirus pandemic. The first and second doses of the Pfizer-BioNTech vaccine are approved to be delivered within a 21-day window, while the Moderna injections should be spread over 28 days. When given at those intervals, both vaccines are about 95% effective, according to the respective drugmakers. But the FDA has heard suggestions that the number of limited doses could be stretched by cutting them in half, extending the length of time between doses, or mixing and matching vaccines in order to immunize more people against COVID-19.
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这是原文出处，看看无毛断章取义的险恶用心。
FDA Statement on Following the Authorized Dosing Schedules for COVID-19 Vaccines
1/4/2021
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We have been following the discussions and news reports about reducing the number of doses, extending the length of time between doses, changing the dose (half-dose), or mixing and matching vaccines in order to immunize more people against COVID-19. 。。。However, at this time, suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence.
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请用事实反驳。
美国食品及药物管理局（FDA）的顾问委员会于周五（26日）开会，全票通过支持使用美国药厂强生的新冠疫苗，为FDA未来数天正式批准紧急使用铺路。一旦成事，将为美国民众提供莫德纳疫苗、辉瑞与BioNTech疫苗以外的第3个选择。
FDA的疫苗和相关生物制品咨询委员会以22票赞成、零票反对，主张向强生疫苗批出紧急使用授权。虽然委员会的建议没有约束力，但FDA一般会采纳。FDA署理局长伍德考克（Janet Woodcock）、FDA生物制品评估与研究中心主任马克斯（Peter Marks）表示，已通知负责分发疫苗的联邦部门，确保准时分配疫苗。
与接种2剂的莫德纳疫苗及辉瑞疫苗相比，强生疫苗只需接种一剂，整体有效率虽然不及前两款疫苗，且对南非变种病毒防护较弱，但专家指可有效预防死亡及住院。共有19.3万人参与强生疫苗的临床测试，数据显示疫苗对长者、孕妇及艾滋病人安全。