Immunogenicity of standard and extended dosing intervals of BNT162b2 mRNA vaccine. Payne et al.

Overview Extension of the interval between vaccine doses for the BNT162b2 mRNA vaccine was introduced in the UK to accelerate population coverage with a single dose. At this time, trial data was lacking, and we addressed this in a study of UK healthcare workers. We aimed to describe the dynamics of T cell and Ab responses after the first dose of BNT162b2 mRNA vaccine over an extended dosing interval, and to compare the magnitude of Ab and T cell responses 4 weeks after dose 2 between short and long vaccination regimens. Human sample and metadata collection HCWs were recruited into the PITCH study at NHS hospitals in five centres in England. All participants received the BNT162b2 Pfizer/BioNTech vaccine at either the "short" dosing interval (3-5 weeks) or "long" dosing interval (6-14 weeks). Peripheral blood was collected and peripheral blood mononuclear cells (PBMCs) and plasma were stored by cryopreservation at -140 oC and -80 oC respectively. Participants were identified as those with samples collected at timepoints of interest (n=589 participants). Long dosing interval accepted timepoints included; - baseline (anytime prior to first dose of vaccine) - 28 days after first vaccine dose (+/- 7 days) - 70 days after first vaccine dose (minimum accepted 40 days. IQR 62/75, range 41 - 129 days), - 28 days after the second vaccine dose (+/- 7 days) - 90 days after the second dose (+/- 7 days) Short dosing interval accepted timepoints included; - baseline (anytime prior to first dose of vaccine) - 7 days after second dose (+ 7days) - 28 days after the second vaccine dose (+/- 7 days) - 90 days after the second dose. Clinical metadata collected included BNT162b2 immunisation dates, date of any prior SARS-CoV-2 infection defined by a positive PCR test and/or detection of antibodies to spike or nucleocapsid protein, presence or absence of symptoms, time between symptom onset and sampling, age, gender and ethnicity of participant. Other metadata included location of study centre. De-identified limited metadata are available here. Options to explore detailed metadata can be sought by contacting the lead author (Paul Klenerman). Data collection Serology and Cellular data were collected from assays using plasma and PBMCs respectively. Serology: MSD and ACE2 assay - Two wells run per test; 1:1000 and 1:10,000 dilution Neutralizing Ab - Serial dilutions were run per test to calculate reduction in number of infected foci - FRNT50 Cellular: ELISpot - Two or three wells run per test ; mean is shown with background subtraction. Total Spike is calculated by adding data from Spike 1 and Spike2 ICS - One run per test compared to positive and negative controls. Results These data on dynamic cellular and humoral responses indicate that extension of the dosing interval is an effective, immunogenic protocol

研究概述
英国为加速单剂BNT162b2 mRNA（messenger RNA）疫苗的人群覆盖范围，推行了延长该疫苗接种间隔的方案。彼时相关临床试验数据尚不完善，本研究针对英国医护人员（healthcare workers, HCWs）展开相关分析以填补这一空白。本研究旨在描述延长接种间隔条件下，首剂BNT162b2 mRNA疫苗接种后T细胞（T cell）与抗体（Antibody, Ab）应答的动态变化，并对比短、长两种接种方案下第二剂接种后4周时抗体与T细胞应答的强度。

人类样本与元数据采集
本研究在英格兰5个中心的英国国民保健署（National Health Service, NHS）医院招募医护人员参与PITCH研究。所有受试者均按照“短间隔”（3~5周）或“长间隔”（6~14周）的接种程序接种BNT162b2辉瑞/百奥泰（Pfizer/BioNTech）疫苗。采集外周血样本，并将外周血单个核细胞（peripheral blood mononuclear cells, PBMC）与血浆分别以-140℃与-80℃冻存。本研究纳入了在关键时间点采集样本的受试者共589例。

长间隔接种组的可接受采样时间点包括：
- 基线期（首剂疫苗接种前任意时间）
- 首剂疫苗接种后28天（±7天）
- 首剂疫苗接种后70天（最低接受时限为40天，四分位距（interquartile range, IQR）为62/75，范围41~129天）
- 第二剂疫苗接种后28天（±7天）
- 第二剂疫苗接种后90天（±7天）

短间隔接种组的可接受采样时间点包括：
- 基线期（首剂疫苗接种前任意时间）
- 第二剂疫苗接种后7天（±7天）
- 第二剂疫苗接种后28天（±7天）
- 第二剂疫苗接种后90天

收集的临床元数据包括：BNT162b2疫苗接种日期、既往任何经PCR阳性检测和/或刺突蛋白或核衣壳蛋白抗体检测阳性定义的严重急性呼吸综合征冠状病毒2（Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2）感染史、有无相关症状、症状发作至采样的时间间隔、受试者年龄、性别与种族。其余元数据包括研究中心所在地点。本数据集提供去标识化的有限元数据，如需查询详细元数据可联系通讯作者Paul Klenerman。

数据采集
分别利用血浆与PBMC样本开展血清学与细胞免疫学检测。
血清学检测：
- MSD与ACE2检测：每份测试设置2个复孔，稀释比例分别为1:1000与1:10000；
- 中和抗体检测：每份测试设置系列稀释样本，以计算感染灶数量的减少幅度，即FRNT50；

细胞免疫学检测：
- ELISpot检测：每份测试设置2或3个复孔，结果以扣除背景后的平均值呈现；总刺突蛋白（Total Spike）的检测结果由刺突蛋白1（Spike1）与刺突蛋白2（Spike2）的数据相加得到；
- ICS检测：每份测试设置1次实验，同时设置阳性与阴性对照。

研究结果
本项关于细胞与体液免疫应答动态变化的数据表明，延长接种间隔是一种有效且具备免疫原性的接种方案。