WHO produces, or provides links to six principle types of guidance documents for national immunization programmes seeking to select the appropriate immunization devices, for prospective IMD-PQS Prequalification Holders, and for laboratories pursuing accreditation:

• complete guidance for prequalfication applicants, for all categories of cold chain-related products: prequalification guidelines that explains how to apply for prequalification and how to maintain prequalification status.
• performance specifications: published standards which set out the detailed performance requirements for an immunization-related product.
• verification protocols: describe in detail how the performance of a product or device will be tested or otherwise evaluated as part of the product prequalification process.
• target product profiles (TPPs): strategic documents that contain a detailed description of desirable future product characteristics, features or functions. They explain the reason for each desirable characteristic and state the date by which the feature is scheduled to be included in the specification and become a requirement for prequalification.
• standard operating procedures (SOPs): ensure that all tasks related to prequalification of immunization products are carried out consistently and systematically.
• supporting information for national immunization programmes: including product selection and assessment tools, volume and capacity calculator tools, study protocols, installation, use and maintenance manuals for prequalified products, relevant technical studies and other product end-user guidance.

Applicants, as well as testing laboratories pursuing accreditation, should consult the relevant performance specifications and verification protocols to enable them to fully complete their applications for evaluation for prequalification or accreditation.

Applicants are also encouraged to consult the TPPs since these will inform them about desirable future product characteristics, features or functions.

All partners and stakeholders are encouraged to consult the SOPs relevant to their operations as part of the process of familiarizing themselves with WHO prequalification procedures.

These guidance documents are developed by WHO in collaboration with national immunization programmes, industry (Prequalification Holders), accredited testing laboratories and a range of technical specialist organizations.

Standards development and revision

WHO is committed to maintaining product specifications and protocols through a process of review, quality enforcement and, when required, revision based on:

• product field-testing
• ongoing user-feedback on product performance in the operating environment
• Prequalification Holders' feedback on root causes of any product challenges as part of the annual review
• industry innovations and other improvements of relevant technologies.