Background

Information regarding the protection conferred by vaccination and previous infection against infection with the B.1.1.529 (omicron) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is limited.

Methods

We evaluated the protection conferred by mRNA vaccines and previous infection against infection with the omicron variant in two high-risk populations: residents and staff in the California state prison system. We used a retrospective cohort design to analyze the risk of infection during the omicron wave using data collected from December 24, 2021, through April 14, 2022. Weighted Cox models were used to compare the effectiveness (measured as 1 minus the hazard ratio) of vaccination and previous infection across combinations of vaccination history (stratified according to the number of mRNA doses received) and infection history (none or infection before or during the period of B.1.617.2 [delta]–variant predominance). A secondary analysis used a rolling matched-cohort design to evaluate the effectiveness of three vaccine doses as compared with two doses.

Results

Among 59,794 residents and 16,572 staff, the estimated effectiveness of previous infection against omicron infection among unvaccinated persons who had been infected before or during the period of delta predominance ranged from 16.3% (95% confidence interval [CI], 8.1 to 23.7) to 48.9% (95% CI, 41.6 to 55.3). Depending on previous infection status, the estimated effectiveness of vaccination (relative to being unvaccinated and without previous documented infection) ranged from 18.6% (95% CI, 7.7 to 28.1) to 83.2% (95% CI, 77.7 to 87.4) with two vaccine doses and from 40.9% (95% CI, 31.9 to 48.7) to 87.9% (95% CI, 76.0 to 93.9) with three vaccine doses. Incremental effectiveness estimates of a third (booster) dose (relative to two doses) ranged from 25.0% (95% CI, 16.6 to 32.5) to 57.9% (95% CI, 48.4 to 65.7) among persons who either had not had previous documented infection or had been infected before the period of delta predominance.

Conclusions

Our findings in two high-risk populations suggest that mRNA vaccination and previous infection were effective against omicron infection, with lower estimates among those infected before the period of delta predominance. Three vaccine doses offered significantly more protection than two doses, including among previously infected persons.

中文翻译：

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防止监狱系统中的 Omicron 接种疫苗和既往感染

背景

关于疫苗接种和既往感染对严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) B.1.1.529 (omicron) 变体感染所提供的保护的信息有限。

方法

我们评估了 mRNA 疫苗和先前感染对两个高危人群（加利福尼亚州监狱系统的居民和工作人员）感染 omicron 变体的保护作用。我们采用回顾性队列设计，使用 2021 年 12 月 24 日至 2022 年 4 月 14 日收集的数据来分析 omicron 波期间的感染风险。加权 Cox 模型用于比较有效性（以 1 减去风险比衡量）疫苗接种史（根据接受的 mRNA 剂量数分层）和感染史（在 B.1.617.2δ-变体优势期间或之前无感染或感染）组合的疫苗接种和既往感染情况。二次分析采用滚动匹配队列设计来评估三种疫苗剂量与两种疫苗剂量相比的有效性。

结果

在 59,794 名居民和 16,572 名工作人员中，在 Delta 优势之前或期间感染过的未接种疫苗的人中，先前感染对 omicron 感染的估计有效性范围为 16.3%（95% 置信区间 [CI]，8.1 至 23.7）至 48.9 %（95% CI，41.6 至 55.3）。根据之前的感染状况，两种疫苗的疫苗接种有效性（相对于未接种疫苗和之前没有记录的感染）的估计有效性范围为 18.6%（95% CI，7.7 至 28.1）至 83.2%（95% CI，77.7 至 87.4）不同剂量的疫苗接种率分别为 40.9%（95% CI，31.9 至 48.7）至 87.9%（95% CI，76.0 至 93.9）。对于之前没有记录的人来说，第三次（加强）剂量（相对于两次剂量）的增量有效性估计范围为 25.0%（95% CI，16.6 至 32.5）至 57.9%（95% CI，48.4 至 65.7）感染或在 Delta 优势期之前已被感染。

结论

我们在两个高危人群中的研究结果表明，mRNA 疫苗接种和既往感染对 omicron 感染有效，在 delta 优势期之前感染的人群中估计值较低。三剂疫苗比两剂疫苗提供了明显更多的保护，包括对以前感染过的人。