Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA; Department of Health Systems Science, Kaiser Permanente Bernard J Tyson School of Medicine, Pasadena, CA, USA.
Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA, USA.
Lancet. 2021 Oct 16;398(10309):1407-1416. doi: 10.1016/S0140-6736(21)02183-8. Epub 2021 Oct 4.
Vaccine effectiveness studies have not differentiated the effect of the delta (B.1.617.2) variant and potential waning immunity in observed reductions in effectiveness against SARS-CoV-2 infections. We aimed to evaluate overall and variant-specific effectiveness of BNT162b2 (tozinameran, Pfizer-BioNTech) against SARS-CoV-2 infections and COVID-19-related hospital admissions by time since vaccination among members of a large US health-care system.
In this retrospective cohort study, we analysed electronic health records of individuals (≥12 years) who were members of the health-care organisation Kaiser Permanente Southern California (CA, USA), to assess BNT162b2 vaccine effectiveness against SARS-CoV-2 infections and COVID-19-related hospital admissions for up to 6 months. Participants were required to have 1 year or more previous membership of the organisation. Outcomes comprised SARS-CoV-2 PCR-positive tests and COVID-19-related hospital admissions. Effectiveness calculations were based on hazard ratios from adjusted Cox models. This study was registered with ClinicalTrials.gov, NCT04848584.
Between Dec 14, 2020, and Aug 8, 2021, of 4 920 549 individuals assessed for eligibility, we included 3 436 957 (median age 45 years [IQR 29-61]; 1 799 395 [52·4%] female and 1 637 394 [47·6%] male). For fully vaccinated individuals, effectiveness against SARS-CoV-2 infections was 73% (95% CI 72-74) and against COVID-19-related hospital admissions was 90% (89-92). Effectiveness against infections declined from 88% (95% CI 86-89) during the first month after full vaccination to 47% (43-51) after 5 months. Among sequenced infections, vaccine effectiveness against infections of the delta variant was high during the first month after full vaccination (93% [95% CI 85-97]) but declined to 53% [39-65] after 4 months. Effectiveness against other (non-delta) variants the first month after full vaccination was also high at 97% (95% CI 95-99), but waned to 67% (45-80) at 4-5 months. Vaccine effectiveness against hospital admissions for infections with the delta variant for all ages was high overall (93% [95% CI 84-96]) up to 6 months.
Our results provide support for high effectiveness of BNT162b2 against hospital admissions up until around 6 months after being fully vaccinated, even in the face of widespread dissemination of the delta variant. Reduction in vaccine effectiveness against SARS-CoV-2 infections over time is probably primarily due to waning immunity with time rather than the delta variant escaping vaccine protection.
Pfizer.
疫苗效力研究并未区分 delta（B.1.617.2）变体的影响和观察到的 SARS-CoV-2 感染效力降低与潜在的免疫衰减之间的关系。我们旨在评估大型美国医疗保健系统中成员接种 BNT162b2（tozinameran，辉瑞-生物技术）后，随着时间的推移，针对 SARS-CoV-2 感染和 COVID-19 相关住院的总体和变体特异性效力。
在这项回顾性队列研究中，我们分析了 Kaiser Permanente Southern California（加利福尼亚州，美国）医疗保健组织成员的电子健康记录，以评估 BNT162b2 疫苗对 SARS-CoV-2 感染和 COVID-19 相关住院的效力，最长可达 6 个月。参与者必须在前一年或更长时间内为该组织的成员。结果包括 SARS-CoV-2 PCR 阳性检测和 COVID-19 相关住院。效力计算基于调整后的 Cox 模型的风险比。这项研究在 ClinicalTrials.gov 上注册，NCT04848584。
在 2020 年 12 月 14 日至 2021 年 8 月 8 日期间，对符合条件的 4920549 人进行了评估，我们纳入了 3436957 人（中位年龄 45 岁[IQR 29-61]；1799395 人[52.4%]为女性，1637394 人[47.6%]为男性）。对于完全接种疫苗的人，针对 SARS-CoV-2 感染的效力为 73%（95%CI 72-74），针对 COVID-19 相关住院的效力为 90%（89-92）。感染效力从完全接种疫苗后的第一个月的 88%（95%CI 86-89）下降到第五个月的 47%（43-51）。在测序感染中，完全接种疫苗后的第一个月，针对 delta 变体感染的疫苗效力很高（93%[85-97]），但在第四个月后下降至 53%[39-65]。在完全接种疫苗后的第一个月，针对其他（非 delta）变体的疫苗效力也很高，为 97%（95%CI 95-99），但在 4-5 个月时下降至 67%（45-80）。所有年龄段 delta 变体感染住院的疫苗效力总体上都很高（93%[84-96]），直到 6 个月。
我们的结果支持 BNT162b2 对完全接种疫苗后长达 6 个月的住院治疗具有很高的效力，即使 delta 变体广泛传播也是如此。随着时间的推移，SARS-CoV-2 感染效力的降低可能主要是由于免疫随时间衰减，而不是 delta 变体逃避疫苗保护。
辉瑞。
