Original vaccines and "bivalent" vaccines
原始疫苗和二价疫苗
The first COVID-19 vaccines remain protective against serious sickness, hospitalization and death, especially after a booster dose.
第一批新冠疫苗对重症、住院及死亡具有保护作用，尤其是在接种加强针之后。
However, drug companies are facing growing pressure to develop vaccines better at fighting off milder infections.
然而制药公司面临越来越大的压力，要求他们开发出能够更好地抵抗轻症的疫苗。
Updating vaccines to match the latest variants is risky, because future variants could be very different. So, companies are considering something like a flu vaccine, which offers protection against three or four different strains in one shot every year.
更新疫苗以匹配最新变种存在风险，因为未来的变种可能会非常不同。所以，公司正在考虑类似流感疫苗之类的东西，它每年打一针，即可针对3到4种不同毒株的保护。
Moderna and Pfizer are testing 2-in-1 COVID-19 protection that they hope to offer this fall. Each "bivalent" shot would mix the original, proven vaccine with an omicron-targeted version.
莫德纳和辉瑞公司正在测试二合一的新冠保护，他们希望能够在今年秋季提供。每种二价疫苗都会将经过验证的原始疫苗与奥密克戎的靶向疫苗混合起来。
Moderna has some early evidence that the idea could work. It tested a combination shot that targeted the original version of the virus and an earlier variant named beta. It found vaccine recipients developed limited levels of antibodies capable of fighting not just beta but also newer variants like omicron. Moderna now is testing its omicron-targeted bivalent candidate.
莫德纳公司的一些早期证据表明该想法可行。它测试了一种针对病毒原始毒株和早期的贝塔变种的组合针剂。它发现疫苗接种者产生的有限抗体水平不仅能够对抗贝塔，而且还能对抗奥密克戎等新变种。莫德纳现在正在测试其针对奥密克戎的二阶候选疫苗。
Boosters
加强针
Dr. David Kimberlin, a CDC adviser from the University of Alabama at Birmingham, recently suggested that for the average person, two doses of the Pfizer or Moderna vaccine plus one booster — a total of three shots — "gets you set up" and ready for what may become a yearly booster.
来自阿拉巴马大学伯明翰分校的美国疾控预防中心顾问戴维·肯柏林最近建议，对于普通人来说，打两针辉瑞或是莫德纳疫苗，再加一针加强针，总共三针，能让你做好可能每年接种一针加强针的准备。
After that first booster, CDC data suggests an additional dose offers most people a small, temporary benefit.
美国疾控预防中心数据表明，在第一针加强针之后，再接种可以为大多数人提供少量、临时的益处。
Experts recommend three shots because vaccination triggers development of antibodies that can fight off coronavirus infection. Such antibody levels naturally decrease over time.
专家建议注射第三针，因为疫苗接种会引发可以抵抗新冠病毒感染的抗体产生。这种抗体水平会随着时间推移自然降低。
But memory cells jump into action to make new virus-fighters if an infection sneaks in. Rockefeller University researchers found those memory cells may become stronger and able to target more diverse kinds of the virus after the third shot.
但是，如果感染潜入，记忆细胞就会开始行动，制造新的抗体。洛克菲勒大学的研究人员发现，这些记忆细胞可能会更变得更加强大，并且在第三针后能够针对更多种类的病毒。
Even if someone who is vaccinated gets a mild infection, memory cells still help give "time to protect you against severe illness," said Dr. Paul Offit of the Children's Hospital of Philadelphia.
费城儿童医院的保罗·奥菲特博士表示，即使接种疫苗的人会受到轻微感染，记忆细胞仍然有助于“保护你免受重症的侵害”。
But some people — those with severely weakened immune systems — need more doses early on for a better chance of protection.
但是免疫系统严重受损的某些人需要在早期接种更多针以获得更好的保护机会。
Americans 50 and older are being offered a second booster, following similar decisions by Israel and other countries that offer the extra shot to give older people a little more protection.
50岁及以上美国人正在接种第二针加强针，在此之前，以色列等国做出类似决定，为老年人提供额外加强针，以给予更多保护。
The CDC is developing advice to help those eligible decide whether to get an extra shot now or wait. Among those who might want a second booster sooner are the elderly, people with health problems or people who are at high risk of exposure from work or travel.
美国疾控预防中心正在制定建议，以帮助符合条件的人们决定是现在多打一针还是继续等待。老年人、有健康问题的人士或因工作或旅行面临高风险的人士可能需要尽快接种第二针加强针。
Nasal vaccines
鼻用疫苗
It is hard for a shot in the arm to form lots of virus-fighting antibodies inside the nose where the coronavirus latches on. But a nasal vaccine might offer a new way to prevent infections.
手臂接种很难在新冠病毒附着的鼻腔内形成大量抗病毒抗体。但是鼻用疫苗可能会提供一种预防感染的新途径。
"When I think about what would make me get a second booster, I actually would want to prevent infection," said Dr. Grace Lee of Stanford University, who chairs CDC's immunization advisory committee. "I think we need to do better."
美国疾控预防中心免疫咨询委员会主席、斯坦福大学的格蕾丝·李博士表示：“当我考虑什么情况能让我去打第二针加强针时，我实际上是想预防感染。我认为我们需要做得更好。”
Nasal vaccines are difficult to develop, and it is not clear how quickly any could become available. But several are in clinical trials around the world. One in late-stage testing, made by India's Bharat Biotech, uses a chimpanzee cold virus to deliver a harmless copy of the coronavirus spike protein to the lining of the nose.
鼻用疫苗很难开发，而且尚不清楚能有多快上市。但是有几种正在世界各地进行临床试验。印度巴拉特生物技术公司进行的一项后期测试使用黑猩猩感冒病毒将冠状病毒刺突蛋白的无害副本传递到了鼻腔内壁。
"I certainly do not want to abandon the success we have had" with COVID-19 shots, said Dr. Michael Diamond of Washington University in St. Louis. Diamond helped create the candidate that is now licensed to Bharat.
圣路易斯华盛顿大学的迈克尔·戴蒙德博士表示：“我当然不想放弃我们在新冠疫苗方面取得的任何成功。”戴蒙德帮助开发了目前授权给巴拉特公司的候选疫苗。
But "we're going to have a difficult time stopping transmission with the current ... vaccines," Diamond added. "We have all learned that."
戴蒙德表示：“我们将会度过一段利用现有疫苗阻断传播的艰难时期。我们都知道这点。”