Background

On July 30, 2021, the administration of a third (booster) dose of the BNT162b2 messenger RNA vaccine (Pfizer–BioNTech) was approved in Israel for persons who were 60 years of age or older and who had received a second dose of vaccine at least 5 months earlier. Data are needed regarding the effect of the booster dose on the rate of confirmed coronavirus 2019 disease (Covid-19) and the rate of severe illness.

Methods

We extracted data for the period from July 30 through August 31, 2021, from the Israeli Ministry of Health database regarding 1,137,804 persons who were 60 years of age or older and had been fully vaccinated (i.e., had received two doses of BNT162b2) at least 5 months earlier. In the primary analysis, we compared the rate of confirmed Covid-19 and the rate of severe illness between those who had received a booster injection at least 12 days earlier (booster group) and those who had not received a booster injection (nonbooster group). In a secondary analysis, we evaluated the rate of infection 4 to 6 days after the booster dose as compared with the rate at least 12 days after the booster. In all the analyses, we used Poisson regression after adjusting for possible confounding factors.

Results

At least 12 days after the booster dose, the rate of confirmed infection was lower in the booster group than in the nonbooster group by a factor of 11.3 (95% confidence interval [CI], 10.4 to 12.3); the rate of severe illness was lower by a factor of 19.5 (95% CI, 12.9 to 29.5). In a secondary analysis, the rate of confirmed infection at least 12 days after vaccination was lower than the rate after 4 to 6 days by a factor of 5.4 (95% CI, 4.8 to 6.1).

Conclusions

In this study involving participants who were 60 years of age or older and had received two doses of the BNT162b2 vaccine at least 5 months earlier, we found that the rates of confirmed Covid-19 and severe illness were substantially lower among those who received a booster (third) dose of the BNT162b2 vaccine.

中文翻译：

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BNT162b2 疫苗增强剂在以色列针对 Covid-19 的保护作用

背景

2021 年 7 月 30 日，以色列批准对 60 岁或以上且曾在至少提前 5 个月。需要有关加强剂量对 2019 年冠状病毒 (Covid-19) 确诊率和重症率影响的数据。

方法

我们从以色列卫生部数据库中提取了 2021 年 7 月 30 日至 8 月 31 日期间的数据，涉及 1,137,804 名 60 岁或以上且至少已完全接种疫苗（即已接种两剂 BNT162b2）的人5个月前。在初步分析中，我们比较了至少 12 天前接受加强注射的人（加强组）和未接受加强注射的人（非加强组）之间的 Covid-19 确诊率和重症率。在二次分析中，我们评估了加强剂量后 4 至 6 天的感染率，并与加强剂量后至少 12 天的感染率进行了比较。在所有分析中，我们在调整可能的混杂因素后使用泊松回归。

结果

加强剂量后至少 12 天，加强剂量组的确诊感染率比非加强剂量组低 11.3 倍（95% 置信区间 [CI]，10.4 至 12.3）；重症率降低了 19.5 倍（95% CI，12.9 至 29.5）。在二次分析中，接种疫苗后至少 12 天的确诊感染率比接种 4 至 6 天后的感染率低 5.4 倍（95% CI，4.8 至 6.1）。

结论

在这项涉及 60 岁或以上且至少 5 个月前接受过两剂 BNT162b2 疫苗的参与者的研究中，我们发现接受加强疫苗的人中确诊 Covid-19 和严重疾病的比率要低得多(第三剂) BNT162b2 疫苗剂量。