辉瑞mRNA原来是打一针能到52%，打两针能到95%。不知中国灭活疫苗是否也是这么计算的？
新英格兰医学如此描述有效率：
The Pfizer and BioNTech covid-19 vaccine may provide some early protection, starting 12 days after the first dose, the peer reviewed results of a phase III trial have found.
The study, published in the New England Journal of Medicine,1 found that vaccine efficacy between the first and second doses was 52% (95% credible interval 29.5% to 68.4%), with 39 cases of covid-19 in the vaccine group and 82 cases in the placebo group.
Seven or more days after the second dose, vaccine efficacy then rose to 95% (90.3% to 97.6%), with eight covid-19 cases reported in the vaccine group and 162 cases in the placebo group.
The vaccine has so far been approved in Canada and in the UK, where it is already being rolled out to people over 80 and healthcare workers. In the US the Food and Drug Administration’s independent panel has voted in favour of emergency use authorisation for the vaccine, and the agency is expected to approve it within days.2
Participants
From July to November 2020, 43 448 adults were randomly assigned at 152 sites worldwide (including in Argentina, Brazil, Germany, South Africa, Turkey, and the US) as part of the phase II/III trial of the BNT162b2 vaccine. A total of 21 720 people received two doses 21 days apart, and 21 728 received a placebo.
科兴生物制药的疫苗在巴西完成三期试验！
Unusual that Brazil released efficacy data ahead of China's Sinovac: Expert - Bing video
https://www.cnbc.com/video/2020/12/24/unusual-that-brazil-released-vaccine-data-before-chinas-sinovac.html
复制以下不是有意揭丑美国。这类疫苗或药物的安全性丑闻在欧美都出现过，这不是中国特产。正因为发生过所以现在药监检控越来越严。中国多年前即全盘引入美国FDA系统并由美国FDA官员常驻中国（现在恐撤回），药物研制中的安全性问题有了很大的进步。对西方药物安全性问题有兴趣的有过生物学基本训练的可以自己查询文献和理解其因果。如有朋友在制药公司做pharmacovigilance工作的更有一手资料向你提供。
PMCID: PMC1383764
The Cutter Incident: How America's First Polio Vaccine Led to a Growing Vaccine Crisis
In April 1955 more than 200 000 children in five Western and mid-Western USA states received a polio vaccine in which the process of inactivating the live virus proved to be defective. Within days there were reports of paralysis and within a month the first mass vaccination programme against polio had to be abandoned. Subsequent investigations revealed that the vaccine, manufactured by the California-based family firm of Cutter Laboratories, had caused 40 000 cases of polio, leaving 200 children with varying degrees of paralysis and killing 10.
J R Soc Med. 2006 Mar; 99(3): 156.
91.25% effective, it's great. I hope all Chinese people can be protected and safe because of effective vaccines, of cause vaccines should be affordable to them.
土耳其研究人员12月24日称，根据在当地第3期临床试验的中期数据显示，北京科兴生物（Sinovac）研发的新冠疫苗（简称“科兴疫苗”）有效率为91.25%。
土耳其研究人员称，除了一人出现过敏反应外，疫苗试验期间没有出现重大副作用事件。他们表示，疫苗引起的常见不良反应是发烧、轻度疼痛及轻度疲劳。
土耳其对科兴疫苗的试验是从9月14日开始，涉及逾7000人，如今这次公布的有效率结果是基于1322人的数据。研究人员又指出，在试验期间有29人感染新冠病毒，其中26人是接受注射安慰剂，试验打算继续进行，直到感染人数升至40人。
当地卫生部长科贾（Fahrettin Koca）表示，“我们现在可以肯定，这款疫苗对土耳其人是有效且安全。”土耳其订购5000万剂科兴疫苗，首批300万剂将在12月28日运抵当地。
在南美国家巴西，当地已完成对科兴疫苗的第3期临床测试，已知通过有效门槛（门槛为有效率起码50%），但科兴12月23日要求押后公布结果15天。《华尔街日报》报道，延后公布结果要求由科兴亲自提出，原因是希望先等待在其他地方测试的结果，再作综合分析后公布。科兴疫苗在巴西、土耳其和印尼都在进行第3期临床测试。
美国辉瑞药厂（Pfizer）之前在11月表示，该药厂研发的疫苗最终数据显示有效率为95%。至于莫德纳（Moderna）疫苗有效率为94%。