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One probable reason why the efficacies recorded by these trials vary so much is that the results from Turkey and Indonesia were based on far fewer participants and fewer recorded cases of covid-19 than those from Brazil. This makes it hard to work out accurate figures for them. Trials in different countries also differ in the way they are run—another possible source of inconsistent findings.

這些試驗記錄的效果差異如此之大的一個可能原因是，土耳其和印度尼西亞疫苗接種者和記錄的新冠病例遠少于巴西，這導(dǎo)致這兩個國家很難計算出準確的數(shù)字。不同國家的臨床試驗的進行方式也有所不同，這可能是導(dǎo)致不同結(jié)果的另一個原因。

The Brazilian trial is the largest, and probably the best run, of the bunch. It involved more that 10,000 volunteers who were health-care workers. Maurício Nogueira, a professor of virology at a state medical school in S?o Paulo, who is one of the principal investigators involved in this trial, points out that 50% is a conservative estimate of the vaccine’s efficacy. He offers three reasons.

• best of the bunch: 一批中最好的

巴西的臨床試驗規(guī)模最大，也可能是最好的。有1萬多名志愿者參與，他們是醫(yī)療工作者。Maurício Nogueira是位于圣保羅的一所國立醫(yī)學(xué)院的病毒學(xué)教授，也是參與這項臨床試驗的主要研究者之一，他指出疫苗效果的保守估計是50%，他給出了三個理由。

One is that, because of the trial participants’ professions, they were more frequently exposed to high concentrations of virus than was the average Brazilian. A second is that health-care workers are more likely than others to notice that they have a symptom of covid-19. The third is that the trial used a particularly sensitive definition of what constituted a potential case of the disease that should therefore be put forward for testing. This was that participants should be tested after reporting only one symptom, rather than three, as demanded by some other trials. The trial’s organisers say that if these “very mild” cases of covid-19 are ignored, and only “mild”, “severe” and “fatal” cases considered, then the vaccine’s efficacy reaches 78%.

一種是，由于臨床試驗參與者的職業(yè)，他們比一般巴西人更頻繁地暴露在高濃度的病毒中。第二，醫(yī)療工作者比其他人更有可能注意到他們有新冠癥狀。第三，該臨床試驗使用了一個特別敏感的定義，即在什么樣的潛在（新冠）疾病癥狀需要進一步測試。這就是說，參與者只有在出現(xiàn)一種（新冠）癥狀后就要進行測試，而不是像其他一些臨床試驗要求的那樣，出現(xiàn)三種癥狀才需上報。臨床試驗的組織者表示，如果忽略這些“非常輕微”的新冠病例，只考慮“輕微”、“嚴重”和“致命”病例，那么疫苗的有效性將達到78%。