On 28 October 2026, PIC/S issued P1058-1 Interpretation of the Most Significant Changes to Annex 1 for the Manufacture of Sterile Medicinal Products. This document entered into force on the same date. Developed jointly by a PIC/S, EMA and WHO working group to align interpretations, the document adopts a Q&A format to clarify critical issues under the revised Annex 1. It delivers a harmonized technical position across the three authorities. This addresses dozens of long-debated industry ambiguities that have persisted since publication of the 2022 version of the sterile Annex 1. Key takeaways are summarised below:
The document clarifies explicitly: VHP is NOT sterilisation
It is repeatedly stated throughout the document that Annex 1 does not classify vapourised hydrogen peroxide (VHP) as a sterilant, due to insufficient robustness and material penetration capability. VHP is only intended for surface bio-decontamination (e.g., material transfer airlocks, isolator systems), which is distinct from sterilisation. Within Annex 1, VHP is categorised as surface bio-decontamination rather than sterilisation.
Lyophiliser decontamination using VHP alone constitutes a deviation
The guidance states that moist heat sterilisation is the preferred method where practicable. Alternative methods may only be considered when moist heat sterilisation is not feasible due to process or material constraints. Lyophilisers shall be designed and operated to permit steam sterilisation. It shall be considered a defect if a lyophiliser is only subjected to VHP bio-decontamination without sterilisation.
Disinfectant rotation is no longer mandatory
The document notes that a disinfectant rotation programme is not a mandatory requirement. However, facilities shall employ more than one class of disinfectant, including periodic use of sporicidal agents. Scheduled rotation of disinfectants and sporicides represents an acceptable approach for cleanroom disinfection. Regardless of whether rotation is implemented, the disinfection programme shall be formally validated to demonstrate efficacy against the expected level of surface bioburden, bacteria and fungi. In addition, ongoing monitoring of disinfection performance forms part of continuous quality management; reviews shall be triggered by major changes, deviations, emerging quality issues and periodic product quality reviews.
Materials may be transferred into Grade C skipping cleanliness grades
In response to the question whether material transfer via airlocks or pass-through chambers must always follow the cleanroom grade gradient sequentially, or whether grade-skipping is permissible under certain conditions (e.g., direct transfer from an unclassified area into Grade C): the response confirms that strict adherence to the cleanliness gradient is not always compulsory for transfer into higher-grade areas. Under conditions fully compliant with Annex 1, grade-skipping is acceptable for material transfer into Grade C.
The A-grade air velocity range of 0.36–0.54 m/s is not an inviolable limit
The guidance clarifies that the uniform air velocity range of 0.36–0.54 m/s for Grade A is advisory, not absolute. Where an operator identifies a potential contamination risk within that range, an alternative air velocity may be adopted following scientific justification within the Contamination Control Strategy (CCS). Such cases shall be supported by airflow visualisation studies correlated with velocity measurements, demonstrating protection of critical operations via first-pass air.
PUPSIT for sterile filters
Clause 8.87 of the document requires that, where practicable, pre-use post-sterilisation integrity testing (PUPSIT) shall be performed on filters used for final sterilisation of solutions and liquids. PUPSIT is not mandatory for other sterile-grade filters deployed for upstream bioburden control within the manufacturing process; their integrity testing shall be risk-based and defined within the CCS. Where redundant filtration is implemented, PUPSIT shall be performed on any filter designated to support batch release. If the redundant filter is not subjected to PUPSIT, a post-use failure of the primary filter cannot be supported by the redundant filter to demonstrate a successful sterile filtration step. Where PUPSIT is impracticable for process-related reasons (rather than design shortcomings), alternative approaches may be acceptable provided they are justified within the CCS, supported by a comprehensive risk assessment prioritising product and patient safety, and accompanied by risk mitigation controls. Risk assessments shall not be inappropriately used to justify omission of PUPSIT.
Contamination Control Strategy (CCS)
Q2 under Section 2.3 states that the CCS is not required to be a single standalone document and no fixed format is specified. Existing controlled quality system documents may be referenced directly without re-writing, provided the CCS defines interfaces between systems to deliver consistent plant-wide contamination control and continuous improvement. Q1 under Section 2.3 recommends CCS effectiveness review at minimum during management review; reviews shall also be conducted upon major changes, deviations, emerging quality issues and periodic product quality reviews. The minimum review frequency is once per year. A CCS remains relevant for non-sterile products where Grade C / Grade D cleanrooms are maintained to achieve low-bioburden product quality.
Environmental monitoring: particle counting at flow rates below 28 L/min is not acceptable
The guidance specifies a minimum sampling flow rate of 28 litres per minute for airborne particle monitoring; lower flow rates are generally unacceptable. The ≥5.0 μm particle limit is not a default classification criterion for Grade A (at rest and in operation) and Grade B (at rest), though these particles shall still be monitored routinely against defined limits.
Environmental monitoring: microbiological testing
For cleanroom re-qualification involving classification (total particle concentration at rest and in operation), active air sampling is not explicitly required. Settling plate limits (Table 6) are defined per plate. Shorter exposure durations (less than 4 hours) do not attract tighter limits, and exposure time shall not be artificially reduced to avoid positive results. Settling plates for Grade A and Grade B shall remain exposed throughout the full duration of critical operations.
Alert and action limits
Annex 1 does not prescribe statistical methods for establishing alert limits; operators may define these methods and document them within their quality system. Where limited historical process data are available, alert limits may initially be established from cleanroom qualification data, then reviewed and adjusted periodically as environmental monitoring datasets mature.
The document contains further Q&A covering facilities, equipment, utilities, personnel, production, environmental monitoring, quality control, specific technologies for sterile manufacture and quality management systems.
