MMWR Morb Mortal Wkly Rep. 2022 Jul 22;71(29):931-939. doi: 10.15585/mmwr.mm7129e1.
The Omicron variant (B.1.1.529) of SARS-CoV-2, the virus that causes COVID-19, was first identified in the United States in November 2021, with the BA.1 sublineage (including BA.1.1) causing the largest surge in COVID-19 cases to date. Omicron sublineages BA.2 and BA.2.12.1 emerged later and by late April 2022, accounted for most cases.* Estimates of COVID-19 vaccine effectiveness (VE) can be reduced by newly emerging variants or sublineages that evade vaccine-induced immunity (1), protection from previous SARS-CoV-2 infection in unvaccinated persons (2), or increasing time since vaccination (3). Real-world data comparing VE during the periods when the BA.1 and BA.2/BA.2.12.1 predominated (BA.1 period and BA.2/BA.2.12.1 period, respectively) are limited. The VISION network examined 214,487 emergency department/urgent care (ED/UC) visits and 58,782 hospitalizations with a COVID-19-like illness diagnosis among 10 states during December 18, 2021-June 10, 2022, to evaluate VE of 2, 3, and 4 doses of mRNA COVID-19 vaccines (BNT162b2 [Pfizer-BioNTech] or mRNA-1273 [Moderna]) compared with no vaccination among adults without immunocompromising conditions. VE against COVID-19-associated hospitalization 7-119 days and ≥120 days after receipt of dose 3 was 92% (95% CI = 91%-93%) and 85% (95% CI = 81%-89%), respectively, during the BA.1 period, compared with 69% (95% CI = 58%-76%) and 52% (95% CI = 44%-59%), respectively, during the BA.2/BA.2.12.1 period. Patterns were similar for ED/UC encounters. Among adults aged ≥50 years, VE against COVID-19-associated hospitalization ≥120 days after receipt of dose 3 was 55% (95% CI = 46%-62%) and ≥7 days (median = 27 days) after a fourth dose was 80% (95% CI = 71%-85%) during BA.2/BA.2.12.1 predominance. Immunocompetent persons should receive recommended COVID-19 booster doses to prevent moderate to severe COVID-19, including a first booster dose for all eligible persons and second booster dose for adults aged ≥50 years at least 4 months after an initial booster dose. Booster doses should be obtained immediately when persons become eligible..
新冠病毒（SARS-CoV-2）的奥密克戎变异株（B.1.1.529）于 2021 年 11 月在美国首次被发现，其 BA.1 亚谱系（包括 BA.1.1）导致了迄今为止最大的 COVID-19 病例激增。奥密克戎亚谱系 BA.2 和 BA.2.12.1 随后出现，截至 2022 年 4 月底，占大多数病例。新出现的变异株或亚谱系会降低 COVID-19 疫苗有效性（VE）的估计值，这些变异株或亚谱系逃避了疫苗诱导的免疫（1）、未接种疫苗者既往 SARS-CoV-2 感染的保护作用（2）或疫苗接种后时间的延长（3）。在 BA.1 和 BA.2/BA.2.12.1 占主导地位的时期（BA.1 期和 BA.2/BA.2.12.1 期）比较 VE 的真实世界数据有限。VISION 网络在 2021 年 12 月 18 日至 2022 年 6 月 10 日期间，对 10 个州的 214487 例急诊/紧急护理（ED/UC）就诊和 58782 例 COVID-19 样疾病住院病例进行了检查，以评估 2、3 和 4 剂 mRNA COVID-19 疫苗（BNT162b2[辉瑞-生物技术]或 mRNA-1273[莫德纳]）与无免疫功能低下状况的成年人未接种疫苗相比的 VE。在 BA.1 期，接受第 3 剂后 7-119 天和≥120 天，与 BA.2/BA.2.12.1 期相比，COVID-19 相关住院的 VE 分别为 92%（95%CI=91%-93%）和 85%（95%CI=81%-89%）；在 BA.1 期，ED/UC 就诊的模式类似。在≥50 岁的成年人中，接受第 3 剂后≥120 天 COVID-19 相关住院的 VE 为 55%（95%CI=46%-62%），接受第 4 剂后≥7 天（中位数=27 天）的 VE 为 80%（95%CI=71%-85%）。在 BA.2/BA.2.12.1 占主导地位期间。免疫功能正常的人应接种推荐的 COVID-19 加强针，以预防中度至重度 COVID-19，包括所有符合条件的人接种第一针加强针，以及至少在初始加强针接种后 4 个月为≥50 岁的成年人接种第二针加强针。当符合条件时，应立即接种加强针。
