Department of Mathematical Sciences, University of Liverpool, Liverpool, UK.
Centre for Global Vaccine Research, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK.
BMC Infect Dis. 2022 Mar 20;22(1):270. doi: 10.1186/s12879-022-07239-z.
From January to May 2021 the alpha variant (B.1.1.7) of SARS-CoV-2 was the most commonly detected variant in the UK. Following this, the Delta variant (B.1.617.2) then became the predominant variant. The UK COVID-19 vaccination programme started on 8th December 2020. Prior to the Delta variant, most vaccine effectiveness studies focused on the alpha variant. We therefore aimed to estimate the effectiveness of the BNT162b2 (Pfizer-BioNTech) and the ChAdOx1 nCoV-19 (Oxford-AstraZeneca) vaccines in preventing symptomatic and asymptomatic infection with respect to the Delta variant in a UK setting.
We used anonymised public health record data linked to infection data (PCR) using the Combined Intelligence for Population Health Action resource. We then constructed an SIR epidemic model to explain SARS-CoV-2 infection data across the Cheshire and Merseyside region of the UK. Vaccines were assumed to be effective after 21 days for 1 dose and 14 days for 2 doses.
We determined that the effectiveness of the Oxford-AstraZeneca vaccine in reducing susceptibility to infection is 39% (95% credible interval [34, 43]) and 64% (95% credible interval [61, 67]) for a single dose and a double dose respectively. For the Pfizer-BioNTech vaccine, the effectiveness is 20% (95% credible interval [10, 28]) and 84% (95% credible interval [82, 86]) for a single-dose and a double dose respectively.
Vaccine effectiveness for reducing susceptibility to SARS-CoV-2 infection shows noticeable improvement after receiving two doses of either vaccine. Findings also suggest that a full course of the Pfizer-BioNTech provides the optimal protection against infection with the Delta variant. This reinforces the need to complete the full course programme to maximise individual protection and reduce transmission.
2021 年 1 月至 5 月，SARS-CoV-2 的 alpha 变体（B.1.1.7）是英国最常见的检测变体。此后，Delta 变体（B.1.617.2）成为主要变体。英国的 COVID-19 疫苗接种计划于 2020 年 12 月 8 日开始。在 Delta 变体之前，大多数疫苗有效性研究都集中在 alpha 变体上。因此，我们旨在估计 BNT162b2（辉瑞-生物科技）和 ChAdOx1 nCoV-19（牛津-阿斯利康）疫苗在英国环境下预防 Delta 变体引起的有症状和无症状感染的有效性。
我们使用联合智能人口健康行动资源，使用匿名公共卫生记录数据与感染数据（PCR）相关联。然后，我们构建了一个 SIR 传染病模型来解释英国柴郡和默西塞德郡地区的 SARS-CoV-2 感染数据。疫苗在接种第一剂后 21 天和第二剂后 14 天被认为是有效的。
我们确定，牛津-阿斯利康疫苗对感染的易感性的降低作用分别为 39%（95%可信区间[34,43]）和 64%（95%可信区间[61,67]），对于一剂和两剂疫苗。对于辉瑞-生物科技疫苗，其有效性分别为 20%（95%可信区间[10,28]）和 84%（95%可信区间[82,86]），对于一剂和两剂疫苗。
接种疫苗可降低 SARS-CoV-2 感染的易感性，两剂疫苗接种后效果明显提高。研究结果还表明，全程接种辉瑞-生物科技疫苗可提供针对 Delta 变体感染的最佳保护。这强化了完成全程接种计划以最大程度地保护个人和减少传播的必要性。
