Objective To compare the effectiveness of a primary covid-19 vaccine series plus booster doses with a primary series alone for the prevention of hospital admission with omicron related covid-19 in the United States. Design Multicenter observational case-control study with a test negative design. Setting Hospitals in 18 US states. Participants 4760 adults admitted to one of 21 hospitals with acute respiratory symptoms between 26 December 2021 and 30 June 2022, a period when the omicron variant was dominant. Participants included 2385 (50.1%) patients with laboratory confirmed covid-19 (cases) and 2375 (49.9%) patients who tested negative for SARS-CoV-2 (controls). Main outcome measures The main outcome was vaccine effectiveness against hospital admission with covid-19 for a primary series plus booster doses and a primary series alone by comparing the odds of being vaccinated with each of these regimens versus being unvaccinated among cases versus controls. Vaccine effectiveness analyses were stratified by immunosuppression status (immunocompetent, immunocompromised). The primary analysis evaluated all covid-19 vaccine types combined, and secondary analyses evaluated specific vaccine products. Results Overall, median age of participants was 64 years (interquartile range 52-75 years), 994 (20.8%) were immunocompromised, 85 (1.8%) were vaccinated with a primary series plus two boosters, 1367 (28.7%) with a primary series plus one booster, and 1875 (39.3%) with a primary series alone, and 1433 (30.1%) were unvaccinated. Among immunocompetent participants, vaccine effectiveness for prevention of hospital admission with omicron related covid-19 for a primary series plus two boosters was 63% (95% confidence interval 37% to 78%), a primary series plus one booster was 65% (58% to 71%), and for a primary series alone was 37% (25% to 47%) (P<0.001 for the pooled boosted regimens compared with a primary series alone). Vaccine effectiveness was higher for a boosted regimen than for a primary series alone for both mRNA vaccines (BNT162b2 (Pfizer-BioNTech): 73% (44% to 87%) for primary series plus two boosters, 64% (55% to 72%) for primary series plus one booster, and 36% (21% to 48%) for primary series alone (P<0.001); mRNA-1273 (Moderna): 68% (17% to 88%) for primary series plus two boosters, 65% (55% to 73%) for primary series plus one booster, and 41% (25% to 54%) for primary series alone (P=0.001)). Among immunocompromised patients, vaccine effectiveness for a primary series plus one booster was 69% (31% to 86%) and for a primary series alone was 49% (30% to 63%) (P=0.04). Conclusion During the first six months of 2022 in the US, booster doses of a covid-19 vaccine provided additional benefit beyond a primary vaccine series alone for preventing hospital admissions with omicron related covid-19. Readers’ note This article is a living test negative design study that will be updated to reflect emerging evidence. Updates may occur for up to two years from the date of original publication. No additional data available.

中文翻译：

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初级系列和加强剂量的疫苗对美国 covid-19 相关住院的疫苗有效性：活体测试阴性设计研究

目的 比较在美国，初级 covid-19 疫苗系列加加强剂量与单独初级系列疫苗在预防 omicron 相关 covid-19 入院方面的有效性。采用测试阴性设计设计多中心观察病例对照研究。在美国18个州设有医院。参与者为 2021 年 12 月 26 日至 2022 年 6 月 30 日期间因急性呼吸道症状入住 21 家医院之一的 4760 名成年人，这一时期 omicron 变异占主导地位。参与者包括 2385 名 (50.1%) 经实验室确诊的 covid-19 患者（病例）和 2375 名 (49.9%) SARS-CoV-2 检测呈阴性的患者（对照）。主要结果指标主要结果是通过比较病例与对照中接种每种方案与未接种疫苗的几率，在初级系列加加强剂量和单独初级系列中，针对 covid-19 入院的疫苗有效性。疫苗有效性分析按免疫抑制状态（免疫功能正常、免疫功能低下）进行分层。初步分析评估了所有 covid-19 疫苗类型的组合，二次分析评估了特定的疫苗产品。结果 总体而言，参与者的中位年龄为 64 岁（四分位间距 52-75 岁），994 名（20.8%）免疫功能低下，85 名（1.8%）接种了初级系列疫苗加两支加强疫苗，1367 名（28.7%）接种了初级疫苗系列加一剂加强疫苗，1875 例（39.3%）仅接种初级系列疫苗，1433 例（30.1%）未接种疫苗。在免疫功能正常的参与者中，使用 omicron 相关的 covid-19 进行初级系列加两剂加强疫苗预防入院的疫苗有效性为 63%（95% 置信区间为 37% 至 78%），初级系列加一剂加强疫苗为 65%（58 % 至 71%），单独的初级系列为 37%（25% 至 47%）（与单独的初级系列相比，合并加强方案的 P<0.001）。两种 mRNA 疫苗（BNT162b2 (Pfizer-BioNTech)）的加强方案的疫苗有效性高于单独的初级系列：初级系列加两个加强方案为 73%（44% 至 87%），64%（55% 至 72%） ）对于初级系列加一个加强剂，对于单独的初级系列为 36%（21% 至 48%）（P<0.001）；mRNA-1273 (Moderna)：对于初级系列加两个加强剂为 68%（17% 至 88%） ，初级系列加一个加强剂为 65%（55% 至 73%），单独初级系列为 41%（25​​% 至 54%）（P=0.001））。在免疫功能低下的患者中，初级系列加一剂加强疫苗的疫苗有效性为 69%（31% 至 86%），单独初级系列的疫苗有效性为 49%（30% 至 63%）（P=0.04）。结论 在美国，2022 年前六个月，加强剂量的 covid-19 疫苗在预防 omicron 相关 covid-19 入院方面比单独的初级疫苗系列提供了额外的益处。读者须知本文是一项活体测试阴性设计研究，将进行更新以反映新出现的证据。自原始发布之日起两年内可能会进行更新。没有其他可用数据。