Carazo Sara, Skowronski Danuta M, Brousseau Nicholas, Guay Charles-Antoine, Sauvageau Chantal, Racine Étienne, Talbot Denis, Ionescu Iulia Gabriela, Fafard Judith, Gilca Rodica, Phimmasone Jonathan, De Wals Philippe, De Serres Gaston
Biological risks unit. Institut national de santé publique du Québec, Quebec City, Quebec, Canada.
Department of social and preventive medicine, Faculty of medicine, Laval University, Quebec City, Quebec, Canada.
PLoS One. 2025 Jun 3;20(6):e0325269. doi: 10.1371/journal.pone.0325269. eCollection 2025.
Vaccine formulations targeting contemporaneous subvariants have been developed to respond to SARS-CoV-2 virus evolution. Updated monovalent COVID-19 vaccines targeting the Omicron XBB.1.5 variant (XBB-vaccines) were administered in the province of Quebec, Canada, during 2023 autumn and 2024 spring vaccination campaigns. Our objective was to evaluate mRNA XBB-vaccine effectiveness (VE) against COVID-19 hospitalizations among adults aged ≥60 years overall during a ten-month follow-up period, by subvariant predominant period, and by time since vaccination.
We conducted a test-negative case-control study using Quebec population-based administrative data. Specimens collected from individuals aged ≥60 years tested at an acute-care hospital from October 2023 to August 2024 were considered test-positive cases if hospitalized for COVID-19, or controls if test-negative for SARS-CoV-2. Vaccination was defined by receipt of at least one mRNA XBB-vaccine (autumn or spring) dose. Subvariant predominant periods were defined according to whole-genome sequencing data from provincial laboratories: XBB or EG.5 and subvariants (XBB period), BA.2.86, JN.1 or subvariants (JN period), and KP.2 or KP.3 and subvariants (KP period). Multivariable logistic regression analyses estimated VE relative to several comparator groups, primarily those last-vaccinated in 2022, by subvariant period, by time since XBB-vaccination and by number of XBB-vaccine doses (KP period).
Participants overall and by XBB, JN and KP periods included: 5532 (4.9%) test-positive cases (1321, 1838 and 1372, respectively) and 108473 (95.1%) test-negative controls (12881, 53414 and 28595, respectively); 14584 specimens were collected during periods of subvariant cocirculation. By subvariant period, 3322 (25.8%), 27041 (50.6%) and 15401 (53.9%) controls, respectively, were considered XBB-vaccinated. Overall VE was 30% (95%CI:24-35) and by XBB, JN or KP period: 54% (95%CI:46-62), 23% (95%CI:13-32) and 0% (95%CI:-18-15), respectively. During each subvariant period, the hospitalization risk was reduced only during the first four months post-vaccination.
Among individuals aged 60 years or older, mRNA XBB-vaccination provided meaningful, albeit limited to first four months post-vaccination, protection against COVID-19 hospitalization due to XBB, JN and KP subvariants. Better vaccines are needed to effectively protect older adults against COVID-19 hospitalizations.
为应对严重急性呼吸综合征冠状病毒2（SARS-CoV-2）病毒的进化，已研发出针对同期亚变体的疫苗配方。2023年秋季和2024年春季疫苗接种活动期间，加拿大魁北克省接种了针对奥密克戎XBB.1.5变体的更新单价新冠疫苗（XBB疫苗）。我们的目标是评估在10个月的随访期内，mRNA XBB疫苗对≥60岁成年人新冠住院治疗的有效性（VE），按亚变体主导期以及自接种疫苗后的时间进行评估。
我们利用基于魁北克省人群的行政数据开展了一项检测阴性病例对照研究。2023年10月至2024年8月在急症医院接受检测的≥60岁个体所采集的样本，如果因新冠住院则视为检测阳性病例，如果SARS-CoV-2检测为阴性则视为对照。接种疫苗定义为接受至少一剂mRNA XBB疫苗（秋季或春季）。亚变体主导期根据省级实验室的全基因组测序数据定义：XBB或EG.5及其亚变体（XBB期）、BA.2.86、JN.1或其亚变体（JN期），以及KP.2或KP.3及其亚变体（KP期）。多变量逻辑回归分析估计了相对于几个比较组的VE，主要是那些在2022年最后接种疫苗的组，按亚变体期、自XBB疫苗接种后的时间以及XBB疫苗剂量数（KP期）进行分析。
总体参与者以及按XBB、JN和KP期划分的参与者包括：5532例（4.9%）检测阳性病例（分别为1321例、1838例和1372例）和108473例（95.1%）检测阴性对照（分别为12881例、53414例和28595例）；在亚变体共同流行期间采集了14584份样本。按亚变体期划分，分别有3322例（25.8%）、27041例（50.6%）和15401例（53.9%）对照被视为接种了XBB疫苗。总体VE为30%（95%置信区间：24 - 35），按XBB、JN或KP期划分分别为：54%（95%置信区间：46 - 62）、23%（95%置信区间：13 - 32）和0%（95%置信区间：-18 - 15）。在每个亚变体期，住院风险仅在接种疫苗后的前四个月降低。
在60岁及以上个体中，mRNA XBB疫苗接种为预防因XBB、JN和KP亚变体导致的新冠住院提供了有意义的保护，尽管这种保护仅限于接种疫苗后的前四个月。需要更好的疫苗来有效保护老年人预防新冠住院。
