预计拜登政府最快将于本周宣布一项推广计划所有人的加强注射得到辉瑞或Moderna的美国人冠状病毒肺炎疫苗八个多月前。
任何计划都将取决于联邦机构是否同意，这些机构表示仍在审查数据。
以下是关于助推器的五件事:
加强注射最早可能在9月中旬开始
去年12月，也就是8个月前，美国第一批疫苗注射给了健康护理人员和养老院居民。
预计这些都是一样的高风险、高优先级群体假设联邦监管机构同意签署，将在9月份率先进行强化注射。
美国美国食品药品监督管理局已经为免疫功能严重受损的人第三次注射开了绿灯。但是这个群体，例如接受癌症治疗或经历过器官移植的患者，被认为一开始就不太可能产生免疫反应。
只有在美国食品和药物管理局同意疫苗制造商和独立研究表明免疫力确实在下降的情况下，才需要为更广泛的公众打预防针。
8个月并不能准确衡量免疫力何时下降
一个人的免疫系统是一个复杂的难题，一个人血液中的抗体只是其中的一部分。
科学家们表示，他们也在寻找其他线索，包括密切关注接种疫苗者的COVID相关住院情况。
辉瑞和BioNTech合作开发了该国的第一种疫苗，该公司表示，有早期数据表明，初始疫苗接种后6至12个月的加强剂量将有助于保持高水平的保护。他们的数据尚未公开分享。
特别是，该公司表示，与接受最初两剂疫苗的人相比，一个人在第一剂疫苗注射后8至9个月注射了增强剂，显示出更高的针对δ变体的中和抗体水平。
但辉瑞和BioNTech也在一份联合声明中表示，他们正在等待更多数据，然后才正式提交允许加强注射的请求。
新的住院数据可能包含更多关于疫苗免疫的线索
接种疫苗的人因COVID相关并发症而住院的人数是疫苗效果如何的重要线索。
如果接种疫苗的人感染了病毒，但没有得重病，也没有将病毒传染给他人，那么疫苗仍然有效。但是，如果卫生官员开始报告越来越多的接种疫苗患者住院，这可能表明接种疫苗人群的免疫力开始下降。
到目前为止，疾病控制和预防中心表示不需要加强剂，估计97%的新冠肺炎住院患者没有接种疫苗。
但这一估计是基于医院报告的春季数据，在三角洲变异开始广泛传播之前。疾控中心表示，它还没有准备好发布更新的数字，但正在努力更清楚地了解达美对疫苗的影响。
食品和药物管理局和疾病预防控制中心仍然需要签字
辉瑞和BioNTech已经向FDA提交了早期数据，但仍在追踪接种疫苗的人。当这些结果最终确定后，预计这些公司将要求美国食品和药物管理局批准第三次注射。
如果美国食品和药物管理局同意，疾控中心的一个独立咨询小组可能会召开会议，讨论到底应该向美国人推荐什么。这将为疾病预防控制中心的官方建议铺平道路，同时为医生和患者提供服用增强剂的建议。
美国食品和药物管理局和疾病预防控制中心此前曾表示，还不需要对更广泛的人群进行强化注射。但是乔·拜登总统的高级医学顾问安东尼·福奇博士称这种可能性是不可避免的，因为随着时间的推移，这种保护可能会减少。
人们对接种强生疫苗的人知之甚少
到目前为止，推出助推器的计划主要集中在依赖类似技术的辉瑞和Moderna疫苗上。
人们对强生疫苗知之甚少，该疫苗的推出时间晚于辉瑞和Moderna，接种人数也少得多。
政府官员表示，预计未来几周将会有更多关于J&J到底允许多少保护的数据，这些信息对于决定J&J接收国是否需要加强保护至关重要。
5 things to know about Biden's plan to roll out COVID boosters this fall
The Biden administration is expected to announce, as soon as this week, a plan to roll outbooster shots for allAmericans who got Pfizer or ModernaCOVIDvaccinesmore than eight months ago.
Any plan would be contingent upon getting a green light from federal agencies who say they are still reviewing the data.
Here are five things to know about boosters:
Booster shots could begin as early as mid-September
The first vaccine shots in the U.S. were given out last December -- exactly eight months ago -- tohealthcare workers and nursing home residents.
It's expected these samehigh-risk, high-priority groupswould be first in line for booster shots come September, assuming federal regulators agree to sign off.
The U.S. Food and Drug Administration has already given the green light for a third shot for people who are severely immunocompromised. But this group -- patients getting treated for cancer or having experienced an organ transplant, for example -- was considered less likely to have developed an immune response in the first place.
Booster shots for the broader public would only be called for if the FDA agrees with vaccine makers and independent studies that immunity is indeed waning.
8 months isn't a precise measure of when immunity wanes
A person's immune system is a complicated puzzle, with antibodies in a person's blood stream as only one piece.
Scientists said they are looking at other clues too, including closely watching COVID-related hospitalizations involving vaccinated people.
Pfizer and BioNTech, which partnered to develop the nation's first vaccine, said it has early data suggesting that a booster dose anywhere from six to 12 months after the initial vaccination will help maintain a high level of protection. Their data have not been shared publicly yet.
In particular, the company said a person getting a booster between eight and nine months after their primary shot showed higher neutralizing antibody levels against the delta variant, compared to people who received the original two doses.
But Pfizer and BioNTech also said in a joint statement that they are waiting for more data before officially submitting a request to allow for booster shots.
New hospitalization data might hold more clues on vaccine immunity
The number of vaccinated people winding up in the hospital with COVID-related complications is an important clue to how well the vaccines are working.
If a vaccinated person becomes infected with the virus but does not become seriously ill or transmit the virus to others, then the vaccine is still working well. But if health officials start reporting a rising number of hospitalizations involving vaccinated patients, that could signal that immunity among vaccinated populations is beginning to wane.
So far, the Centers for Disease Control and Prevention has said boosters aren't needed, estimating that 97% of people hospitalized with COVID-19 are unvaccinated.
But that estimate was based on hospital-reported data from spring, before the delta variant began spreading wildly. The CDC said it's not ready to release updated numbers yet, but is working on getting a clearer picture of delta's impact on the vaccines.
The FDA and CDC still have to sign off
Pfizer and BioNTech have submitted early data to the FDA, but are still tracking people who got the vaccine. When those results are finalized, the companies are expected to ask the FDA to green light the third shots.
If the FDA signs off, an independent advisory panel to the CDC will likely convene to discuss what exactly should be recommended to Americans. That would then pave the way for an official recommendation by the CDC, along with advice to doctors and patients on getting a booster.
undefinedMORE: More kids are getting sick from COVID. Is it delta?
The FDA and CDC have said previously that booster shots for broader populations aren't needed yet. But Dr. Anthony Fauci, the top medical adviser to President Joe Biden, has called the possibility inevitable because of the likelihood that protection would diminish over time.
Less is known about people who got the Johnson & Johnson vaccine
So far, the plan to roll out boosters is focused on Pfizer and Moderna vaccines, which rely on similar technology.
Less is known about the Johnson & Johnson vaccine, which rolled out later than Pfizer and Moderna and has been given to considerably fewer people.
Government officials say more data are expected in coming weeks on precisely how much protection J&J allows -- information that will be critical in determining whether J&J recipients might need a boost.
