Evaluation of the quality, safety and efficacy of mRNA vaccines for the prevention of infectious diseases: regulatory considerations

评估用于预防传染病的 mRNA 疫苗的质量、安全性和有效性：监管方面的考虑因素

 7. Nonclinical evaluation of mRNA vaccines

7.mRNA 疫苗的非临床评估

The nonclinical evaluation of candidate mRNA vaccines should be considered on a product-    specific basis taking into account the intended clinical use. The design, conduct and analysis   of nonclinical studies including selection of appropriate studies relating to the “pharmacology” (in the case of vaccines, immunogenicity and proof-of-concept) and toxicology of the product    should be based on the following WHO guidelines:

候选 mRNA 疫苗的非临床评估应根据产品的具体情况加以考虑，同时考虑到预期的临床用途。非临床研究的设计、实施和分析，包括选择与产品的 "药理学"（就疫苗而言，免疫原性和概念验证）和毒理学有关的适当研究，应遵循以下世卫组织准则：

WHO guidelines on nonclinical evaluation of vaccines (16); and WHO  Guidelines  on  the  nonclinical   evaluation   of  vaccine   adjuvants   and adjuvanted vaccines (17).

世界卫生组织疫苗非临床评估指南 (16)；以及世卫组织疫苗佐剂和佐剂疫苗非临床评估指南 (17)。

 There are several potential concerns that need to be considered during the safety and proof-of-concept evaluations of mRNA vaccines. Because of the novelty of this product type, numerous issues are addressed below which may be relevant to any given mRNA vaccine. However, there may also be future additional concerns that come to light that would need to be taken into consideration when appropriate. Not all of these issues will necessarily be relevant to any given mRNA vaccine, depending on its design. However, it is incumbent upon the vaccine developer/manufacturer to provide evidence demonstrating the proof-of- concept  (for  example,  immunogenicity  and,  if an  appropriate  animal  model  is  available, challenge protection) and safety of their candidate vaccine. The types, design and number of studies expected should be agreed with the NRA.

在对 mRNA 疫苗进行安全性和概念验证评估时，需要考虑几个潜在的问题。由于这种产品类型的新颖性，下文将讨论许多可能与任何特定 mRNA 疫苗相关的问题。不过，未来可能还会出现其他问题，需要在适当的时候加以考虑。并非所有这些问题都与任何特定的 mRNA 疫苗相关，这取决于疫苗的设计。不过，疫苗开发商/生产商有责任提供证据，证明其候选疫苗的概念验证（例如免疫原性，如果有适当的动物模型，还包括挑战保护）和安全性。预期研究的类型、设计和数量应与国家兽医局商定。

7.1     Pharmacology/immunology/proof-of-concept

7.1 药理学/免疫学/概念验证

 In addition to the types of studies discussed in the WHO guidelines above (16, 17), additional issues that the NRA might expect nonclinical studies to address may include:

除了上述世卫组织指南（16、17）中讨论的研究类型外，NRA 可能希望非临床研究解决的其他问题还包括

 a.   Durability of immune responses or immune cell phenotypes that suggest durability, particularly  those  that  are  proposed  to  be  related  to  the  candidate  vaccine’s  induction   of   protection.   To   assess   the    durability   of   immune   responses,  characterization of immune cell phenotypes and/or cytokine expression could be  helpful in investigating persistence and memory responses.

a. 免疫反应或免疫细胞表型的持久性，尤其是与候选疫苗诱导保护有关的表型。 为评估免疫反应的持久性，免疫细胞表型和/或细胞因子表达的特征可能有助于研究持续性和记忆性反应。

b.   Induction  of  innate  immune  responses  by  RNA  (such  as  induction  of type  I interferon), which have been reported to decrease translation of the target antigen or that could affect the need for (or timing of) boosts or subsequent doses.

b. 诱导先天性免疫反应的 RNA（如诱导 I 型干扰素），有报道称这种反应会降低目标抗原的翻译，或可能影响加强或后续剂量的需要（或时间）。

 7.2     Safety/toxicity in animal models

7.2 动物模型的安全性/毒性

In  addition  to  the  expectations  outlined  in  the  WHO  guidelines  listed  above  (16,  17),  consideration should be given to whether studies need to be designed to address the following:

除了上述世界卫生组织指南（16、17）中列出的预期目标外，还应考虑是否需要针对以下方面设计研究：

a.   Biodistribution  and  persistence: developing a database of evidence about this potential  concern will permit the more rapid  development  of future  candidate vaccines (3, 64–69). This potential issue may also depend on whether the vaccine migrates to specific cells or tissues. Nonclinical studies that address whether the mRNA and the LNPs (or lipid components) distribute away from the tissue into which the vaccine was administered, into which tissues they distribute and how long they persist may be expected by the NRA. Agreement on these studies should be sought from the NRA.

a. 生物分布和持久性：建立有关这一潜在问题的证据数据库将有助于更快地开发未来的候选疫苗 (3,64-69)。这一潜在问题可能还取决于疫苗是否会迁移到特定的细胞或组织。非临床研究可解决 mRNA 和 LNPs（或脂质成分）是否从接种疫苗的组织扩散、扩散到哪些组织以及持续多久的问题，这可能是国家生物制品监管局所期望的。应就这些研究征得 NRA 的同意。

b.   Inflammation: RNA is inflammatory via a number of pathways, particularly via  the innate immune system with its numerous sensors for RNA. In mRNA vaccines, both the mRNA molecules and the LNPs (which enable successful delivery and  cellular uptake) have properties that can influence and trigger the innate immune  system (70,  71). While some of this activity may be beneficial for the immune  response to the vaccine, it will be important to monitor for both systemic and local  toxicity and inflammatory responses. Nonclinical study design needs to take into  account  any  immune  responses,  reactogenicity  or  toxicities  that  might  predict  immune indicators (70, 71) of serious adverse events or adverse events of special  interest (AESI) in humans. Additionally, other components added to aid delivery,  such as PEG, although relatively benign, can also influence the physicochemical  properties  and  thus   the  safety  profile   (72–75).  It  is  therefore   important  to  understand  the  overall  product  profile  including  the  formulation  and  how  physicochemical properties (which may vary) can influence inflammation and the  safety profile. The choice of animal model will, as always, be critical, recognizing  that   anti-RNA   innate   immune   responses   in   animal   models   are   generally  significantly milder than those observed in humans.

b. 炎症：RNA 可通过多种途径引起炎症，特别是通过先天性免疫系统及其对 RNA 的众多感应器。在 mRNA 疫苗中，mRNA 分子和 LNPs（可成功递送并被细胞吸收）都具有可影响和触发先天性免疫系统的特性（70, 71）。虽然其中一些活性可能有利于疫苗的免疫反应，但监测全身和局部毒性及炎症反应也很重要。非临床研究设计需要考虑到任何可能预测人体严重不良事件或特别关注不良事件（AESI）的免疫指标（70、71）的免疫反应、反应原性或毒性。此外，为帮助给药而添加的其他成分（如 PEG）虽然相对无害，但也会影响理化性质，从而影响安全性（72-75）。 因此，了解包括配方在内的整个产品概况以及理化特性（可能会有所不同）如何影响炎症和安全性概况非常重要。动物模型的选择一如既往地至关重要，因为动物模型中的抗 RNA 先天免疫反应通常比在人体中观察到的反应要温和得多。

 c.   Unexpected  and serious toxicities from modified nucleosides: some antivirals and anti-cancer drugs that contained specific unnatural nucleoside analogues with altered conformation have caused mitochondrial toxicities, resulting in myopathy, polyneuropathy,  lactic  acidosis,  liver  steatosis,  pancreatitis,  lipodystrophy  and even  fatality.  However,  some  of these  clinically  observed  toxicities  were  not observed in the nonclinical animal models used. While the modified nucleosides used in the most advanced mRNA vaccines (against COVID-19) are naturally occurring, future candidate vaccines may contain modifications that are unnatural. Thus,   particularly   for   mRNA   vaccines   that   include   unnatural   nucleoside modifications that have not already been well characterized in other developed nucleic-acid-based products, careful consideration will need to be given to how these potential toxicities might be observed  in  appropriate  animal models  and nonclinical studies during safety evaluation (76–78).

c. 改性核苷的意外严重毒性：一些抗病毒和抗癌药物含有改变构象的特定非天然核苷类似物，会引起线粒体毒性，导致肌病、多发性神经病、乳酸酸中毒、肝脏脂肪变性、胰腺炎、脂肪变性，甚至死亡。 然而，在所使用的非临床动物模型中并没有观察到其中一些临床观察到的毒性。虽然最先进的 mRNA 疫苗（针对 COVID-19）中使用的修饰核苷是天然存在的，但未来的候选疫苗可能含有非天然的修饰。因此，特别是对于含有非天然核苷修饰的 mRNA 疫苗，如果其他已开发的基于核酸的产品尚未对这些修饰进行很好的描述，那么在安全性评估过程中，就需要仔细考虑如何在适当的动物模型和非临床研究中观察到这些潜在的毒性 (76-78)。

 d.   Novel lipids  and  novel LNPs: because the lipids used to formulate the LNPs affect the overall charge of the particle, when using LNPs made with novel lipids or  when  the  LNPs  are  themselves  modified   (for  example,   altered  ratios  or modified processes) and these LNPs have not previously been nonclinically and clinically tested in mRNA products encapsulated in LNPs, then evaluation of the toxicity  of  the  new  formulation  containing  the  novel  lipids  (or  any  novel excipients)  may  be  required.  Furthermore,  the  NRA  may  require  that  the genotoxicity  and  systemic  toxicity  of the  novel  lipid  component  be  assessed, similar to the expectations for novel adjuvants set out in the WHO Guidelines on the  nonclinical  evaluation  of vaccine  adjuvants  and  adjuvanted  vaccines  (17) and/or those for new chemical entities in the ICH guideline S2 (R1)

d. 新型脂质和新型 LNPs：由于用于配制 LNPs 的脂质会影响颗粒的整体电荷，当使用新型脂质制成的 LNPs 时，或当 LNPs 本身经过改良（例如，改变比例或改良工艺）且这些 LNPs 以前未在封装在 LNPs 中的 mRNA 产品中进行过非临床和临床测试时，可能需要对含有新型脂质（或任何新型辅料）的新制剂进行毒性评估。 此外，NRA 可能会要求对新型脂质成分的遗传毒性和全身毒性进行评估，这与世界卫生组织《疫苗佐剂和佐剂疫苗非临床评估指南》(17) 和/或 ICH 指南 S2 (R1) 中对新型化学实体的要求相似。

e.   Novel  formulations:  likewise,  for  formulations  (other  than  LNPs)  containing novel excipients, data on and assessment of the systemic toxicity and genotoxicity of the formulation may be expected.

e. 新型制剂：同样，对于含有新型赋形剂的制剂（LNPs 除外），可能需要提供有关制剂的系统毒性和遗传毒性的数据并进行评估。

It  should  be  noted  that  early  theoretical  concerns  during  plasmid  DNA  vaccine development regarding the potential for integration of vaccine nucleic acids into the host genome do not apply to mRNA vaccines for the following reasons:

值得注意的是，由于以下原因，早期在质粒 DNA 疫苗开发过程中对疫苗核酸可能整合到宿主基因组的理论担忧并不适用于 mRNA 疫苗：

     The only known mechanism by which RNA can integrate into the host genome requires the presence of a complex containing reverse transcriptase and integrase.

RNA 与宿主基因组整合的唯一已知机制要求存在包含逆转录酶和整合酶的复合物。

     Further, the design of candidate mRNA vaccines should be considered so that they do not include specific RNA-binding sites for primers required for the reverse transcriptase to  initiate  transcription.  In  addition,  the  RNA  would  have  to  be relocated to the nucleus after reverse transcription for the resulting product to be integrated.

此外，在设计候选 mRNA 疫苗时应考虑到它们不包括反转录酶启动转录所需的引物的特定 RNA 结合位点。 此外，反转录后的 RNA 必须转移到细胞核中，才能整合所产生的产物。

     Finally, the vaccine mRNA degrades within a relatively short time once taken up by the body’s cells, as does the cell’s own mRNA. During that entire time, the mRNA vaccine is expected to remain in the cytoplasm, where it will be translated and then degraded by normal cellular mechanisms.

最后，疫苗的 mRNA 一旦被人体细胞吸收，就会在相对较短的时间内降解，细胞自身的 mRNA 也是如此。在整个过程中，mRNA 疫苗预计会留在细胞质中，在那里进行翻译，然后被正常的细胞机制降解。

 Therefore, nonclinical studies do not need to be performed to specifically address integration or genetic risks for mRNA vaccines.

因此，无需针对 mRNA 疫苗的整合或遗传风险开展非临床研究。

As with any vaccine that is anticipated to be used widely in pregnant women or women  of  childbearing  potential,  the  guidance  provided  in  section  4.2.2  of  the  WHO Guidelines  on  nonclinical  evaluation  of  vaccines   (16)  and  section  D.2.3  of  the  WHO Guidelines on the nonclinical evaluation of vaccine adjuvants and adjuvanted vaccines (17) should be consulted. The necessity for such studies will be based on the target population for the given clinical indication of the vaccine. Often, if required, these studies are performed during  or  after  pivotal  clinical  trials  have  been  performed  with  the  candidate  vaccine produced using commercial manufacturing methods and scale. As a result, data should be available at the time of filing for marketing authorization on populations that include women of childbearing potential, and such data should be evaluated prior to the intentional enrolment of pregnant women in clinical studies.

对于任何预计将广泛用于孕妇或有生育能力妇女的疫苗，都应参考《世界卫生组织疫苗非临床评估指南》 (16) 第 4.2.2 节和《世界卫生组织疫苗佐剂和佐剂疫苗非临床评估指南》(17) 第 D.2.3 节中提供的指导。此类研究的必要性取决于疫苗特定临床适应症的目标人群。如果需要，这些研究通常会在使用商业生产方法和规模生产的候选疫苗进行关键临床试验期间或之后进行。因此，在申请上市许可时，应获得包括育龄妇女在内的人群数据，并在有意让孕妇参与临床研究之前对这些数据进行评估。

If  clinical   data   from   similar  candidate  vaccines  based  on  the  same  platform technology are available, then agreement should be reached with the NRA on whether or not such data are scientifically sufficient to preclude the need for further nonclinical studies. If nonclinical  safety  data  from  similar  candidate  vaccines  based  on  the  same  platform technology are available, agreement should also be reached with the NRA on whether or not such  data  are  scientifically  sufficient  to  preclude  the  need  for  further  nonclinical  safety studies. Likewise, nonclinical safety data (and if available, clinical data) from a monovalent drug product formulation can support the clinical development of a multivalent drug product formulation (for example, for different strains of the same disease antigen) or combination vaccine (different disease antigens) in cases where the same LNP with the same molar and mRNA–lipid ratios is used, and where the sum of all the mRNAs in the multivalent drug product  formulation  will  be  no  more  than  the  highest  dose   shown  to  be   safe  in  the monovalent nonclinical safety study.

如果可以获得基于相同平台技术的类似候选疫苗的临床数据，则应与 NRA 就这些数据在科学上是否足以排除进一步非临床研究的必要性达成一致。如果有基于相同平台技术的类似候选疫苗的非临床安全性数据，也应与 NRA 就这些数据是否科学地足以排除进一步非临床安全性研究的必要性达成一致。同样，来自单价药物产品制剂的非临床安全性数据（如有，临床数据）也可支持多价药物产品制剂的临床开发（例如，用于同一疾病不同菌株的抗病毒药物）、同样，如果使用相同摩尔比和 mRNA 脂质比的相同 LNP，且多价药物产品制剂中所有 mRNA 的总和不超过单价非临床安全性研究中显示的最高安全剂量，则多价药物产品制剂（例如，针对同一疾病抗原的不同菌株）或联合疫苗（不同疾病抗原）的临床开发也可得到支持。

 7.3     Accelerating  nonclinical   evaluation  in  the  context  of  rapid  vaccine development against a priority pathogen during a public health emergency In the case of the rapid development of vaccines against a priority pathogen during a public health emergency and when the new candidate vaccines are based on a given manufacturer’s platform technology, consideration may be given to an abbreviated nonclinical programme as follows:

7.3 在突发公共卫生事件期间针对重点病原体快速开发疫苗的情况下加快非临床评估 在突发公共卫生事件期间针对重点病原体快速开发疫苗的情况下，当新的候选疫苗基于特定制造商的平台技术时，可考虑缩短非临床计划，具体如下：

     Where changes are made to the sequence of the target antigen  encoded in an mRNA vaccine that has already been clinically tested (for example, in the case of a pandemic influenza strain when a seasonal or other potential pandemic strain antigen has been tested, or where a variant SARS-CoV-2 spike protein arises), where the same LNPs are used (that is, same lipid composition and mRNA–lipid ratio, and where the total amount of mRNAs and LNPs per dose remain equal to or below that clinically tested) and where an approved manufacturing process is used, then, depending on NRA requirements, the nonclinical programme might be limited to an immunogenicity study (or studies) or a challenge-protection study (or studies) in a relevant animal model, if available. As much safety information as  feasible  should  be  collected  during  these  immunogenicity  or  challenge- protection  studies  on  the  understanding  that  such  nonclinical  proof-of-concept studies  are  generally  performed  without   full  compliance  to  good  laboratory practices (GLP). If safety information on veterinary vaccines expressing related antigens is available, this might also be useful and should be provided. Any other information concerning the safety of the platform technology used should also be provided for NRA consideration, for example, prior toxicology and biodistribution study data.

如果已通过临床试验的 mRNA 疫苗中编码的目标抗原序列发生变化（例如，在大流行流感病毒株的情况下，季节性或其他潜在的大流行病毒株抗原已通过试验，或出现了变异的 SARS-CoV-2 尖峰蛋白），使用相同的 LNPs（即相同的脂质成分和 mRNA 脂质比、如果使用相同的 LNPs（即相同的脂质成分和 mRNA 脂质比，每剂量的 mRNA 和 LNPs 总量等于或低于临床测试的总量），并采用经批准的生产工艺，那么，根据非驻地机构的要求，非临床计划可能仅限于在相关动物模型中进行免疫原性研究（或多项研究）或挑战保护研究（或多项研究）（如果有的话）。在这些免疫原性或挑战保护研究中应收集尽可能多的安全性信息，但有一项谅解，即此类非临床概念验证研究通常是在不完全符合良好实验室规范 (GLP) 的情况下进行的。如果可以获得表达相关抗原的兽用疫苗的安全性信息，这可能也是有用的，应予以提供。还应提供与所用平台技术的安全性有关的任何其他信息，例如先前的毒理学和生物分布研究数据，以供国家生物资源管理局考虑。

     Where the LNPs have been tested clinically with an unrelated mRNA such that the target antigen is novel (that is, not related to another antigen that has been clinically  tested),  then  the  approach  of  limiting   nonclinical   studies   to  an immunogenicity  or  challenge-protection  study  might  not  be  sufficient.  The decision regarding what type of nonclinical safety/toxicology information should be required might be guided by consideration of what and how much is known about  the  natural  disease  in  terms  of  its  pathology.  If  the  natural  disease  is associated  with  immunopathology  due  to  cross-reactivity,  molecular  mimicry, autoimmunity,  allergenicity  or  immunity-associated  disease  enhancement,  then toxicology studies would likely be needed to ensure that the novel target antigen was  not  associated  with  these  effects.  It  should  be  noted  that  it  may  not  be possible to investigate autoimmunity in nonclinical studies (16). Where natural disease is not associated with immunopathology or where little is known about the natural  disease,  discussion  with  the  NRA  should  be  undertaken  on  how  the nonclinical programme might be abbreviated.

如果 LNP 已经用一种不相关的 mRNA 进行了临床测试，而目标抗原又是新的抗原（即与另一种已经过临床测试的抗原无关），那么将非临床研究局限于免疫原性或挑战-保护性研究的方法可能就不够充分了。 在决定需要哪种类型的非临床安全性/毒理学信息时，可以考虑从病理学角度对自然疾病的了解程度。 如果自然疾病与交叉反应、分子模拟、自身免疫、过敏性或免疫相关疾病增强等免疫病理有关，则可能需要进行毒理学研究，以确保新型目标抗原与这些效应无关。 需要注意的是，在非临床研究中可能无法调查自身免疫（16）。如果自然疾病与免疫病理无关，或对自然疾病知之甚少，则应与非临床研究机构讨论如何缩短非临床研究计划。

     Finally, where the LNPs and the encoded target antigen (and hence the mRNA structure  and  sequence)  are  both  novel,  nonclinical  evaluation  may  be  more complex and more extensive studies may be required; thus, discussion with the NRA  should  also  be  undertaken  and  it  may  not  be  possible  to  significantly abbreviate the nonclinical programme. However, it may be possible to initiate clinical studies while some of the required nonclinical studies are being performed in parallel with (or slightly ahead of) clinical development.

最后，如果 LNPs 和编码的靶抗原（以及 mRNA 结构和序列）都是新的，非临床评估可能会更复杂，需要进行更广泛的研究。不过，在进行某些必要的非临床研究的同时（或略早于临床开发），也有可能启动临床研究。

 Decisions on abbreviating the nonclinical programme should always take into account what is already known about related and previously tested products, particularly if based on the same platform technology. If clinical data from a related product(s) are available, these data are

在决定缩减非临床计划时，应始终考虑到相关产品和以前测试过的产品的已知情况，特别是基于相同平台技术的产品。如果有相关产品的临床数据，这些数据应

likely to be more meaningful for evaluating the safety of the candidate vaccine in humans than data from any given animal model or from an in vitro human model.

与任何特定动物模型或体外人体模型的数据相比，这些数据可能对评估候选疫苗在人体中的安全性更有意义。

 8. Clinical evaluation of mRNA vaccines

8.mRNA 疫苗的临床评估

 The clinical evaluation expectations for clinical trial authorization or marketing authorization will  be  driven  by  the  disease  against  which  the  mRNA  vaccine  is  being  or  has  been developed and the vaccine mode-of-action (or mechanism-of-action). If an immune correlate of protection has been identified this may change the expectations compared to what might be expected in the absence of such a correlate. Clinical studies should adhere to the principles described   in   the   WHO   Guidelines   for   good   clinical   practice   (GCP)   for   trials   on pharmaceutical products (23) and the WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18). Post-marketing pharmacovigilance is also discussed in the latter guidelines. Furthermore, these same guidelines provide considerations in evaluating dosing regimens, clinical development plans, boosting, collection of safety data, designs for pivotal efficacy   trials   (including   potential   end-points),   standardizing   immunogenicity   assays (including use of IS and reporting of data in IU) and immunobridging to infer efficacy (18). Considerations for studies during pregnancy are also discussed in these same guidelines.

临床试验授权或上市授权的临床评估预期将取决于正在开发或已经开发的 mRNA 疫苗所针对的疾病以及疫苗的作用模式（或作用机制）。如果已经确定了保护的免疫相关因素，与没有这种相关因素时的预期相比，可能会改变预期。临床研究应遵守《世界卫生组织药品试验良好临床实践 (GCP) 指南》(23) 和《世界卫生组织疫苗临床评估指南：监管期望》(18) 中描述的原则。后者还讨论了上市后的药物警戒问题。此外，这些指南还提供了评估给药方案、临床开发计划、强化、安全性数据收集、关键疗效试验设计（包括潜在终点）、免疫原性测定标准化（包括使用 IS 和以 IU 为单位报告数据）以及免疫桥接以推断疗效等方面的注意事项（18）。这些指南还讨论了孕期研究的注意事项。

Clinical trials should capture safety, immunogenicity and efficacy data, as expected for any other type of vaccine, but with particular consideration given to the potential concerns outlined below as these may be more relevant for mRNA vaccines than for other types of vaccines that might already be licensed and with which regulators might be more familiar.

临床试验应获取安全性、免疫原性和有效性数据，与任何其他类型疫苗的预期一样，但应特别考虑下文概述的潜在问题，因为这些问题可能与 mRNA 疫苗相比更相关，而其他类型疫苗可能已获得许可，监管机构可能更熟悉这些问题。

8.1     Safety and immunogenicity evaluation

8.1 安全性和免疫原性评估

 Sufficient data should be obtained from preliminary clinical studies to permit evaluation of the following safety and immunological aspects that may be particularly relevant to mRNA vaccines:

应从初步临床研究中获得足够的数据，以便对以下可能与 mRNA 疫苗特别相关的安全性和免疫学方面进行评估：

 a.   Adverse immune effects

a. 不良免疫效应

Transient decreases in lymphocytes (Grades 1–3) a few days after vaccination were reported in the interim human clinical trial results of an mRNA COVID-19 vaccine, with lymphocytes returning to baseline within 6–8 days in all participants and with no associated clinical observations  (79).  Such transient  drops have been observed for other vaccines and have resulted in no significant deleterious effect on the immune response  (80,  81).  Because  RNA  induces  type   1   interferons,  which  have  been associated with the transient migration of lymphocytes into tissues, the phenomenon of  any   effect  on  lymphocyte  counts  in  blood  may  need  specific  attention  in preliminary clinical trials (67, 82–84). Nonetheless, because this phenomenon may be important for the immune response to the candidate vaccine, it may be important to observe whether changes in leukocyte counts and  subsets are associated with any adverse   clinical   signs   or   symptoms.   Thus,    the    monitoring   of    appropriate reactogenicity parameters  in  the  immediate  post-vaccination  period  is  paramount. Further general guidance on safety evaluation is provided in section 7 of the WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18).

mRNA COVID-19 疫苗的中期人体临床试验结果显示，接种几天后淋巴细胞出现短暂下降（1-3 级），但所有参与者的淋巴细胞均在 6-8 天内恢复到基线水平，且未出现相关临床症状（79）。 其他疫苗也出现过这种瞬时下降，但对免疫反应无明显有害影响（80、81）。 由于 RNA 可诱导 1 型干扰素，而 1 型干扰素与淋巴细胞向组织的短暂迁移有关，因此在初步临床试验中可能需要特别注意对血液中淋巴细胞数量的任何影响（67、82-84）。不过，由于这种现象可能对候选疫苗的免疫反应很重要，因此观察白细胞数量和亚群的变化是否与任何不良临床症状或体征有关可能很重要。 因此，在接种疫苗后的第一时间监测适当的反应性参数至关重要。世卫组织《疫苗临床评价指南：监管期望》（18）第 7 节提供了有关安全性评价的更多一般指导。

 b.   Types and scope of immune responses In  addition  to  the  type  and  scope  of  immunogenicity  described  in  the  WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18), in studies in   which   immunogenicity   is   measured,    additional   facets   of   the    safety   and immunogenicity of mRNA vaccines may include:

b. 免疫反应的类型和范围 除了《世界卫生组织疫苗临床评价指南：监管期望》（18）中描述的免疫原性类型和范围外，在测量免疫原性的研究中，mRNA 疫苗安全性和免疫原性的其他方面可能包括： 1：

     whether the mRNA candidate vaccine biases towards certain types of immune responses, depending on what is known about the natural disease and the vaccine mode-of-action. To date, two clinical studies of COVID-19 mRNA vaccines have noted a Th1-type bias (35, 41). This information may be useful for predicting and understanding the impact of the immune responses for a particular disease.

mRNA 候选疫苗是否会偏向于某些类型的免疫反应，这取决于对自然疾病和疫苗作用模式的了解程度。迄今为止，COVID-19 mRNA 疫苗的两项临床研究已注意到 Th1 型偏向（35、41）。这些信息可能有助于预测和了解免疫反应对特定疾病的影响。

     as with any new vaccine, any instances or evidence of AESI as defined in the WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18) or of any other novel adverse event should be captured in clinical trials and in post-marketing  evaluation.  If so,  then  investigations  should  be  conducted  into associations and potential causes, such as whether unwanted immune responses against vaccine components  (such  as RNA  or lipids)  are generated or,  if pre- existing  in  the  vaccine  recipient,  are  increased  or  exacerbated.  Alternatively, epitope mimicry due to the responses to the expressed antigen(s) may need to be investigated.

与任何新疫苗一样，应在临床试验和上市后评估中捕捉《世界卫生组织疫苗临床评估指南：监管期望》（18）中定义的任何 AESI 或任何其他新型不良事件的实例或证据。 如果是，则应调查其关联性和潜在原因，如是否产生了针对疫苗成分（如 RNA 或脂质）的不良免疫反应，或者如果疫苗受种者体内已经存在不良免疫反应，是否会增加或加剧不良反应。 或者，可能需要对表达抗原的反应引起的表位模仿进行调查。

Consideration  should  also be  given  to the total  dose  of mRNA  (especially  if the vaccine is a multivalent or combination vaccine, or an sa-mRNA vaccine where separate mRNAs are used) and to the total dose of LNPs with regard to the maximally tolerable dose determined  during  the  development  of  an  mRNA  vaccine.  For  platform  technologies,  a maximally tolerable dose for a given population may be suggested by the dose previously determined for vaccines (or candidate vaccines) produced using that platform.

还应考虑 mRNA 的总剂量（特别是如果疫苗是多价疫苗或联合疫苗，或使用单独 mRNA 的 sa-mRNA 疫苗）以及 LNP 的总剂量，并参照 mRNA 疫苗开发过程中确定的最大耐受剂量。 对于平台技术而言，特定人群的最大耐受剂量可参考先前使用该平台生产的疫苗（或候选疫苗）所确定的剂量。

If boosting following a primary dose or series is being considered due to waning effectiveness, careful evaluation of any increased frequency or severity of local or systemic reactions  should  be  performed.  As  with  all  vaccines,  it  is  recommended  that  a  careful exploration of dose, timing and number of immunizations (primary series and boosters if needed),  and  kinetics  and  durability  of  immune  responses  be  performed  in  preliminary clinical trials to guide the design of the efficacy trial(s). Discussion of these issues can be found in section 5.5 of the WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18). In certain situations, a determination that booster doses are needed might not be made until post-marketing data have been collected (for example, indicating waning immunity or protection). The above Guidelines (18) also discuss the boosting of licensed vaccines in section 5.6.1.2.3, which addresses the situation in which an alternative posology to the licensed product may need to be developed for the booster. Waning protection and the necessity for booster doses is then discussed in section 6.3.8. (18). Differences between the vaccine and circulating strains, including the potential need to add or replace strains, are briefly discussed in section 5.3.3 and other sections that discuss influenza vaccines, for which strain changes are frequently made.

如果由于效果减弱而考虑在初次接种或系列接种后加强免疫，则应仔细评估局部或全身反应的频率或严重程度是否增加。 与所有疫苗一样，建议在初步临床试验中仔细探讨免疫剂量、时间和次数（初次免疫和必要的加强免疫），以及免疫反应的动力学和持久性，以指导疗效试验的设计。有关这些问题的讨论可参见《世界卫生组织疫苗临床评估指南：监管期望》（18）第 5.5 节。在某些情况下，可能要等到收集到上市后的数据（例如显示免疫力或保护作用减弱）后才能确定是否需要加强剂量。上述《指南》(18) 还在第 5.6.1.2.3 节中讨论了已获许可疫苗的加强剂量问题，该节讨论了可能需要为加强剂量开发已获许可产品的替代姿势的情况。随后，第 6.3.8 节讨论了保护作用减弱和加强剂量的必要性 (18)。第 5.3.3 节和其他讨论流感疫苗的章节简要讨论了疫苗与流行毒株之间的差异，包括可能需要添加或替换毒株，因为流感疫苗经常会更换毒株。

It should be noted that during clinical trials or widespread use of COVID-19 mRNA vaccines, immunologically relevant adverse events of particular note (such as anaphylaxis or anaphylactoid reactions) have been observed (85, 86). Anaphylaxis is known to occur very rarely with all vaccines and is not unique to mRNA vaccines. It is not yet known what aspect of the formulation is associated with immunological adverse events and it is advised, as with other vaccines, that individuals with known allergies to specific vaccine components should not  be  vaccinated  with  vaccines  containing  such  components  (87–90).  Myocarditis  and pericarditis have also been observed during COVID-19 mRNA vaccine pharmacovigilance and  appear  to  be  associated  –  though  the  biological  mechanism  and  associated  vaccine component have not yet been  identified  (91,  92).  It  should  further  be  noted  that  recent publications by several regulatory authorities provide useful relevant information, including publications by the European Medicines Agency  (69,  93), the Medicines  and  Healthcare products Regulatory Agency (87, 94) and the US Food and Drug Administration (90, 95).

值得注意的是，在 COVID-19 mRNA 疫苗的临床试验或广泛使用过程中，观察到了一些值得特别注意的免疫相关不良事件（如过敏性休克或过敏性反应）（85、86）。据了解，过敏性休克在所有疫苗中都极少发生，并非 mRNA 疫苗所独有。目前尚不清楚制剂的哪方面与免疫不良反应有关，建议与其它疫苗一样，对特定疫苗成分过敏的人不应接种含有此类成分的疫苗 (87-90)。 在 COVID-19 mRNA 疫苗药物警戒期间也观察到心肌炎和心包炎，似乎与此有关--尽管生物机制和相关疫苗成分尚未确定（91, 92）。 还应指出的是，一些监管机构最近的出版物提供了有用的相关信息，包括欧洲药品管理局（69、93）、药品与保健品管理局（87、94）和美国食品药品管理局（90、95）的出版物。

In  line  with  the  WHO  Guidelines  on  clinical  evaluation  of  vaccines:  regulatory expectations (18), the establishment and implementation of active pharmacovigilance plans are recommended.  In  the  specific  case  of COVID-19  or  other  vaccines  deployed  in  the context of a public health emergency, consideration should also be given to running a public awareness campaign on potential adverse events. As with any new vaccine, all adverse events potentially associated with COVID-19 vaccines are currently being further assessed as part of pharmacovigilance activities.

根据《世界卫生组织疫苗临床评估指南：监管期望》（18），建议制定并实施积极的药物警戒计划。 对于 COVID-19 或其他在公共卫生突发事件中使用的疫苗，还应考虑就潜在的不良事件开展公众宣传活动。与任何新疫苗一样，作为药物警戒活动的一部分，目前正在进一步评估可能与 COVID-19 疫苗相关的所有不良事件。

Given the short period for and limited scope of safety studies as part of the efficacy studies that have led to the current widespread use of COVID-19 mRNA vaccines, and the still unknown long-term safety impacts of mRNAs formulated with LNPs in large human populations, it will be important to continue monitoring and recording rare adverse events that have an unknown relationship with the use of such vaccines. Regulatory agencies should analyze such data for vaccines made by different manufacturers to provide a better clinical understanding  and  a  more  precise  safety  profile  for  mRNA  vaccines  in  the  current formulation designs. Furthermore, manufacturers and public health agencies should consider conducting   post-introduction    vaccine   effectiveness    studies,   addressing    questions    of effectiveness  among  specific  at-risk  groups,  the  duration  of protection,  and  effectiveness against both infection and transmission. As stated above, this is a rapidly evolving area and significant new data are emerging on an ongoing basis.

鉴于作为目前广泛使用 COVID-19 mRNA 疫苗的疗效研究的一部分而进行的安全性研究时间短、范围有限，而且在大量人群中使用 LNP 配制的 mRNA 的长期安全性影响仍然未知，因此必须继续监测和记录与使用此类疫苗有未知关系的罕见不良事件。监管机构应对不同制造商生产的疫苗的此类数据进行分析，以便更好地了解临床情况，并对当前配方设计中的 mRNA 疫苗提供更准确的安全性概况。此外，制造商和公共卫生机构应考虑开展疫苗上市后的有效性研究，解决特定高危人群的有效性、保护持续时间以及预防感染和传播的有效性等问题。如上所述，这是一个快速发展的领域，新的重要数据不断涌现。

When  international  standards  expressed  in  IU  are  available  for  standardizing  the immune assays used in clinical evaluation of the vaccine, they should be used to calibrate internal standards or other working reference materials, and results should be reported in IU to improve the comparability of results across vaccines, across studies and across different assay platforms.

如果有以 IU 表示的国际标准可用于疫苗临床评估中所用免疫测定的标准化，则应使用这些标准校准内部标准或其他工作参考材料，并以 IU 为单位报告结果，以提高不同疫苗、不同研究和不同检测平台结果的可比性。

 8.2     Efficacy evaluation

8.2 功效评估

 Efficacy  evaluation will depend upon the disease against which the candidate vaccine is intended  to protect,  and  the  clinical  indication  determined  in  clinical  trials.  Factors  that should  be  considered  in  the  evaluation  of  vaccine  efficacy  are  described  in  the  WHO Guidelines on clinical evaluation of vaccines: regulatory expectations (18).

效力评估将取决于候选疫苗旨在预防的疾病以及临床试验中确定的临床适应症。 世卫组织《疫苗临床评估指南：监管期望》（18）中介绍了疫苗功效评估中应考虑的因素。

It should be noted that in countries in which COVID-19 mRNA vaccines are currently being widely used, the use of placebo controls in trials requires special consideration. The ethical considerations regarding the conducting of ongoing COVID-19 vaccine trials with placebo controls were discussed in open public meetings held in December 2020 (96, 97). Trial design issues (including the selection of appropriate comparators) are discussed in the above WHO Guidelines (18). Further guidance is also provided in the outcome document of a WHO Expert consultation on the use of placebos in vaccine trials (98). As with all candidate vaccines, both the scientific merits and ethical considerations should inform the trial design and  decisions must be made  in the  current benefit–risk  context  of the  country  in which regulatory authorization is being sought (99, 100). In addition, WHO has now published more than 70 Guidelines and Recommendations for vaccines against specific diseases, any one or several  of which may provide relevant  guidance  on the  evaluation  of any  given mRNA vaccine.

需要注意的是，在目前广泛使用 COVID-19 mRNA 疫苗的国家，试验中使用安慰剂对照需要特别考虑。2020 年 12 月举行的公开会议讨论了正在进行的 COVID-19 疫苗试验中使用安慰剂对照的伦理考虑因素（96、97）。上述《世卫组织指南》（18）讨论了试验设计问题（包括选择适当的参照物）。世卫组织关于在疫苗试验中使用安慰剂的专家咨询成果文件中也提供了进一步的指导（98）。与所有候选疫苗一样，试验设计应考虑科学价值和伦理因素，并且必须在寻求监管授权的国家当前的收益-风险背景下做出决定（99, 100）。此外，世卫组织现已发布了 70 多项针对特定疾病的疫苗指南和建议，其中任何一项或几项都可为任何特定 mRNA 疫苗的评估提供相关指导。

8.3     Efficacy evaluation in the context of a public health emergency in which immune-escape and other variants arise

8.3 在出现免疫逃逸和其他变异情况下的公共卫生紧急情况下的药效评估

As discussed in section 5.6.2 of the WHO Guidelines on clinical evaluation of vaccines: regulatory  expectations  (18)  it  may be  feasible to  consider immunobridging between the manufacturer’s original candidate vaccine (or subsequently marketed vaccine) and a variant candidate vaccine in order to infer efficacy of the variant mRNA candidate vaccine based on a manufacturer’s given platform technology in which clinical end-point efficacy has been demonstrated for the original candidate (or marketed) vaccine. The immunobridging may have to be supported by justification of how comparable antibody titres for the prototype and variant vaccines would translate into similar efficacy. Consideration must be given to the following  scenarios:  (a)  the  variant  candidate vaccine will  replace the  original  candidate vaccine; or (b) the variant and original candidate vaccines will be combined (that is, in a bivalent or multivalent vaccine) or administered simultaneously or in sequence. Collection of comparative safety data during such immunobridging studies will also be expected. Overall, the considerations for immunobridging studies may depend upon factors such as the disease, pathogen and induced immune response(s) – trial designs and data requirements should thus be decided on an individual case-by-case basis.

正如《世界卫生组织疫苗临床评估指南：监管期望》(18) 第 5.6.2 节中所讨论的，可以考虑在生产商的原始候选疫苗（或随后上市的疫苗）和变体候选疫苗之间进行免疫桥接，以便根据生产商的给定平台技术推断变体 mRNA 候选疫苗的功效，其中原始候选疫苗（或上市疫苗）的临床终点功效已得到证实。在进行免疫桥接时，可能需要说明原型疫苗和变体疫苗抗体滴度的可比性如何转化为相似的疗效。必须考虑以下情况： (a) 变体候选疫苗将取代原始候选疫苗；或 (b) 变体疫苗和原始候选疫苗将合并（即二价或多价疫苗）或同时或依次接种。预计在此类免疫桥接研究中还将收集安全性对比数据。总体而言，免疫桥接研究的考虑因素可能取决于疾病、病原体和诱导的免疫反应等因素，因此应根据具体情况决定试验设计和数据要求。

In  the  specific  case  of  COVID-19  vaccines,  consideration  may  be  given  to  the guidance  provided  by  WHO  (101,  102),  the  European  Medicines  Agency  (69,  93),  the Medicines and Healthcare products Regulatory Agency  (87,  94), the US Food  and Drug Administration (90, 95) and other regulatory authorities (103–105).

就 COVID-19 疫苗的具体情况而言，可考虑世卫组织 (101、102)、欧洲药品管理局 (69、93)、药品和保健品监管局 (87、94)、美国食品和药物管理局 (90、95) 及其他监管机构 (103-105) 提供的指导。

Currently, mRNA vaccines  against  influenza  viruses  are  in  development  and  any proposed strain changes may have to take into consideration current practices for inactivated or live attenuated influenza virus vaccines. The WHO recommendations to assure the quality, safety,   and   efficacy    of   influenza   vaccines   (human,    live   attenuated)   for   intranasal administration (106) and WHO Recommendations for the production and control of influenza vaccine (inactivated) (107) should be consulted.

目前，针对流感病毒的 mRNA 疫苗正在开发中，任何拟议的菌株变化可能都必须考虑到灭活或减活流感病毒疫苗的现行做法。应参考世卫组织关于确保鼻内给药流感疫苗（人类，减毒活疫苗）的质量、安全性和有效性的建议 (106) 和世卫组织关于流感疫苗（灭活疫苗）生产和控制的建议 (107)。