LIB and LEITV Laboratories, Instituto Gonçalo Moniz, Fiocruz, Salvador, Bahia, Brazil.
Universidade Federal de Bahia (UFBA), Salvador, Bahia, Brazil.
PLoS Med. 2023 Jan 11;20(1):e1004156. doi: 10.1371/journal.pmed.1004156. eCollection 2023 Jan.
Brazil and Scotland have used mRNA boosters in their respective populations since September 2021, with Omicron's emergence accelerating their booster program. Despite this, both countries have reported substantial recent increases in Coronavirus Disease 2019 (COVID-19) cases. The duration of the protection conferred by the booster dose against symptomatic Omicron cases and severe outcomes is unclear.
Using a test-negative design, we analyzed national databases to estimate the vaccine effectiveness (VE) of a primary series (with ChAdOx1 or BNT162b2) plus an mRNA vaccine booster (with BNT162b2 or mRNA-1273) against symptomatic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection and severe COVID-19 outcomes (hospitalization or death) during the period of Omicron dominance in Brazil and Scotland compared to unvaccinated individuals. Additional analyses included stratification by age group (18 to 49, 50 to 64, ≥65). All individuals aged 18 years or older who reported acute respiratory illness symptoms and tested for SARS-CoV-2 infection between January 1, 2022, and April 23, 2022, in Brazil and Scotland were eligible for the study. At 14 to 29 days after the mRNA booster, the VE against symptomatic SARS-CoV-2 infection of ChAdOx1 plus BNT162b2 booster was 51.6%, (95% confidence interval (CI): [51.0, 52.2], p < 0.001) in Brazil and 67.1% (95% CI [65.5, 68.5], p < 0.001) in Scotland. At ≥4 months, protection against symptomatic infection waned to 4.2% (95% CI [0.7, 7.6], p = 0.02) in Brazil and 37.4% (95% CI [33.8, 40.9], p < 0.001) in Scotland. VE against severe outcomes in Brazil was 93.5% (95% CI [93.0, 94.0], p < 0.001) at 14 to 29 days post-booster, decreasing to 82.3% (95% CI [79.7, 84.7], p < 0.001) and 98.3% (95% CI [87.3, 99.8], p < 0.001) to 77.8% (95% CI [51.4, 89.9], p < 0.001) in Scotland for the same periods. Similar results were obtained with the primary series of BNT162b2 plus homologous booster. Potential limitations of this study were that we assumed that all cases included in the analysis were due to the Omicron variant based on the period of dominance and the limited follow-up time since the booster dose.
We observed that mRNA boosters after a primary vaccination course with either mRNA or viral-vector vaccines provided modest, short-lived protection against symptomatic infection with Omicron but substantial and more sustained protection against severe COVID-19 outcomes for at least 3 months.
自 2021 年 9 月以来，巴西和苏格兰一直在各自的人群中使用 mRNA 加强针，随着奥密克戎的出现，加速了他们的加强针计划。尽管如此，这两个国家最近都报告了大量的 COVID-19 病例增加。针对奥密克戎症状病例和严重结果的加强针保护持续时间尚不清楚。
我们使用了一种阴性对照设计，分析了国家数据库，以估计在奥密克戎占主导地位期间，与未接种疫苗的个体相比，用 ChAdOx1 或 BNT162b2 进行初级系列（加用 BNT162b2 或 mRNA-1273）加 mRNA 疫苗加强针（用 BNT162b2 或 mRNA-1273）对有症状的严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）感染和严重 COVID-19 结局（住院或死亡）的疫苗有效性（VE）。此外的分析包括按年龄组（18 至 49 岁、50 至 64 岁、≥65 岁）进行分层。在巴西和苏格兰，所有年龄在 18 岁或以上、在 2022 年 1 月 1 日至 4 月 23 日期间报告急性呼吸道疾病症状并接受 SARS-CoV-2 感染检测的个体都有资格参加这项研究。在接受 mRNA 加强针后 14 至 29 天，用 ChAdOx1 加 BNT162b2 加强针的 VE 对有症状的 SARS-CoV-2 感染为 51.6%（95%置信区间[51.0，52.2]，p < 0.001）在巴西，为 67.1%（95%置信区间[65.5，68.5]，p < 0.001）在苏格兰。≥4 个月后，对有症状感染的保护作用减弱至 4.2%（95%置信区间[0.7，7.6]，p = 0.02）在巴西，37.4%（95%置信区间[33.8，40.9]，p < 0.001）在苏格兰。在巴西，接种加强针后 14 至 29 天，对严重结局的 VE 为 93.5%（95%置信区间[93.0，94.0]，p < 0.001），下降至 82.3%（95%置信区间[79.7，84.7]，p < 0.001）和 98.3%（95%置信区间[87.3，99.8]，p < 0.001），至 77.8%（95%置信区间[51.4，89.9]，p < 0.001）在苏格兰同期。用 BNT162b2 加同源加强针的初级系列也得到了类似的结果。本研究的潜在局限性是，我们假设根据优势期和加强针后有限的随访时间，分析中包括的所有病例都是由于奥密克戎变异引起的。
我们观察到，在接受 mRNA 或病毒载体疫苗的初级疫苗接种后使用 mRNA 加强针，对奥密克戎症状感染提供了适度的、短暂的保护，但对严重 COVID-19 结局提供了实质性的、更持久的保护，至少持续 3 个月。
