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VHP (Vapour Hydrogen Peroxide) Fragility

Posted by: , Posted on: - Categories: Compliance matters, Good manufacturing practice

I have been the chairperson for the revision of Annex 1 of the EU and PIC/S GMPS for the manufacture of sterile medicinal products for a couple of years now. As such I engaged with stakeholders and other regulators to understand their wishes and concerns. One particular topic that has come up as a discussion point at a number of the more recent conferences that gives me great concern, and this is around how to sterilise direct and indirect product contact items in an isolator. I therefore felt it was time to go into print regarding the agency’s view.

A number of manufacturers are looking at isolator technology in new or existing facilities, which is great to hear, but the fly in the ointment, is that the consideration of how to sterilise direct and indirect contact parts does not always form part of the design process. But before I go further I will clarify what I mean by indirect and direct product contact parts:

Indirect product contact parts, as the name implies, are equipment parts that come into contact with items and components, such as stoppers. So, although the equipment itself does not contact the product the items that are “processed” by the equipment do.

Direct contact parts are those that the product passes through, such as filling needles or pumps.

The issue that is arising is that a number of manufacturers are not including robust systems of sterilisation, such as autoclaves, dry heat or offsite irradiation in their facility designs. This leaves a situation where the Agency is being asked, why Vapour Hydrogen Peroxide (VHP) cannot be used for “sterilisation” of these direct and indirect product contact parts. After all, pharmacopeias refer to VHP as a sterilising agent. However, our concern is that although under ideal conditions, VHP can achieve a reduction of biological Indicator spores of up to 6 logs, the process itself is incredibly fragile.

A pile of papers and foldersIf we cast our minds back a number of years, when VHP was being used to decontaminate the internal surfaces of isolators (not the indirect or direct contact parts) there were a number of issues seen with biological indicators failing the process due to clumping of spores at a microscopic level. This led to a number of papers being written (such as “Biological indicators don’t lie, but in sporicidal gassing disinfection cycles do they sometimes confuse the truth?”, European Journal of Parenteral & Pharmaceutical Sciences 2009; 14(1): 5-10 © 2009 Pharmaceutical and Healthcare Sciences Society) that justified biological indicator failure at one or two locations based on statistical analysis. The papers also recommended that a number of indicators (usually 3) be placed at each location to demonstrate a 3 log reduction (which is not a sterilisation process). This, along with other evidence, such as VHP failure due to very minor occlusion, even to the degree that fatty acids from a fingerprint may “protect” contaminating organisms from the VHP demonstrate the true fragility of the process as a sterilant.

If we then consider the design of some of the indirect and direct product contact parts, we find that a number of them are either difficult to achieve VHP penetration, or, damage and wear and tear can leave surfaces that lead to difficulty to clean and therefore potential occlusion.

VHP, when well controlled and validated, is a useful method for the decontamination of the surrounding workspace, e.g. an isolator environment. However, given the above concerns, our current stance is that VHP cannot be used to sterilise critical items. Even if some of the concerns can be removed by well thought out processes, this still leaves the sterilisation at risk of the vagaries of manual process during set up. For instance, how many of us see ‘human error’ as a high percentage of root cause errors during deviation investigations? Therefore, it would be a high risk option and potentially leave the patient at risk from such a fragile process.

So, what are we expecting?

Our expectation is that the contact parts (direct and indirect) are sterilised using a robust sterilisation method that meets the current requirements of annex 1. This means that:

the sterilising agent reaches all of the critical surfaces in a consistent and repeatable manner, typically requiring processes such as moist or dry heat sterilisation.

the item is unloaded from the sterilisation process either wrapped in integral covering or container, or is transferred under grade A conditions, such as a transfer isolator into the manufacturing isolator.

We also expect that the parts are not exposed to the isolator environment until the isolator has been closed and after completion of the work zone decontamination VHP cycle.

We continue to move increasingly into a pharmaceutical world governed by the principles of quality risk management. We are unable to say that VHP will never be an acceptable approach. However, manufacturers who are considering a different approach to sterilisation, or to any other GMP requirement, seek a dialogue with the agency at an early stage. This may save on costly modification later on in the project and who knows, you may even receive some useful help! The GMP Inspectorate can be approached in a number of ways, one is through the Innovation Office, or by E mail to the GMP Inspectorate directly


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  1. Comment by Sandip V. Patel posted on

    Hi Andew,
    An interesting way it is presented. Thanks for wonderful blog. One statement written as "there were a number of issues seen with biological indicators failing the process due to clumping of spores at a microscopic level." What I believe that isolator when it is cleaned (suppose manually) ,closed and HEPA is continuously ON, it flush away all the particles and have a clean grade A air in the isolator. The limit of viable particle is <1cfu. My thought- When we are claiming it as grade A environment where there is less chance of the microorganism and no chance of spore as a clump (i mean no more than one spore together), and so there could be instance that BI may fail due to clumping of spore while cycle qualification (which can be resolved by Halvorson-Ziegler equation) but in actual routine sterilization it will work. Isn't it?

    • Replies to Sandip V. Patel>

      Comment by Sara Berry posted on

      Dear Sandip,
      The reason for mentioning the spore clumping was not the issue of biologicals indicators per se, but, as a further example of how the process is very weak in terms of penetration and thus the concern is that in adequate cleaning or manual hadnling could cause occlusion of organisms that would go undetected but could cause contamination of the product.
      Kind Regards

  2. Comment by Jugal K Raghuwanshi posted on

    It, S very much informative

  3. Comment by Prakash Deshmukh posted on

    Very useful information
    Thanks for sharing agency's views

  4. Comment by Nicholas Clark posted on

    This is an excellent and very helpful post Andrew. Thank you for taking the time to explain the Agency's thinking and rationale - long may it continue.

  5. Comment by Sandip V. Patel posted on

    Hi Andrew,
    Thanks for wonderful article with good referencing of the facts.
    What about indirect contact parts such as star-wheel/track on filling machine which can not to be sterilized via heat ?. Currently most of the industries are proceed it through cleaning and disinfection with frequent usage of sporicidal agent. Is it necessary to sterilize such items too? How?

    • Replies to Sandip V. Patel>

      Comment by Sara Berry posted on

      As per the article, we are referencing indirect product contact parts that then contact component surfaces that contact product e.g. the inside of stoppers of vials. Generally items like star wheels do not contact a surface that will then contact the product as the tend to contact the outside of vials etc, in this case we would refer to them as change parts and would accept a validated sanitisation/disinfection process, as with a more traditional line. If these parts are contacting internal surfaces then they would need to be sterilised by some method, irradiation, E beam etc could be considered.

  6. Comment by brian fox posted on

    Is there any MHRA view on the use of Enzymatic Indicators (using thermally stable Adenylate Kinase) to verify H2O2 effectiveness ?

    • Replies to brian fox>

      Comment by Sara Berry posted on

      Dear Brian,
      The Inspectorate has seen some information on these systems and generally they seem to offer a reasonable approach especially, as they appear to give a quantitative response rather than just a binary response. This appears to give the potential for a better understanding of the cycles. However, as with all alternative methods, it is for the user to show the appropriateness of the method and suppliers used and capture this (scientific rationale) in their PQS.
      Kind regards

  7. Comment by Simon Rattenbury posted on

    Dear all
    One of the main issues with VHP is that it’s a vapour and does not obay the gas laws like other gaseous sterilants such as formaldehyde , chlorine dioxide (dry) and ethylene oxide.
    Another issue with VHP is inactivated by bacteria producing catalase such as TB, Staphs, etc
    Chlorine dioxide is not affected by these and achieve s a 6 log reduction consistently

  8. Comment by Ravi Menon posted on

    VHP decon is a surface phenomenon and one must expect difficulties in killing when spores in strips clump together forming multi-layers. VHP cannot 'penetrate' multilayers, it can only 'settle'.

    Would a handling approach where there is
    a) A step to wash the stopper contact parts
    b) A step to wrap and sterilize the stopper contact parts
    c) To bring the sterilized parts into the isolator via open door and mount it in position [A sort of Grade A in Grade C assembly]
    d) Close doors and carry out VHP
    work to meet expectations?

    This way the Steam sterilization does the heavy lifting of the microbial kill and the VHP deals only with the minimal potential organisms that could be present due to assembly under Grade A with Grade C surround?

    • Replies to Ravi Menon>

      Comment by Janet Symes posted on

      Dear Ravi
      There may be a number of different approaches that could be possible, but it is not possible to judge and comment on specifics without a significant amount of detail behind the processes stated below. If there is a specific process that you wish to discuss, please contact the inspectorate directly.