How much shelf life must remain on delivery?

What remaining shelf life measures

How much shelf life must be remaining on delivery of medicines is a question WHO answers in months rather than in percentages. Technical Report Series No. 1044, Annex 8 defines remaining shelf life as the period remaining from the date of delivery to the expiry date, retest date, install-by date or other use-before date established by the manufacturer. Two things follow from that wording.

The first is that the period is measured from delivery. Not from the date the certificate was issued, and not from the date you are reading it. The second is that it does not always run to an expiry date. Where a material carries a retest date instead, the retest date is the end point, and a passed retest date means something different from a passed expiry date.

Delivery is itself a defined term in the same glossary, and it is not a fact about the shipment. It is the date a medical product is delivered as specified, for example at the port, at the point in-country after customs clearance, or at the end user, and as defined in the agreement between relevant parties. The delivery point is settled by contract. A requirement stated without one is incomplete.

The months the example table asks for

Appendix 1 of the annex carries a single table of minimum remaining shelf life at three points: dispatch from the manufacturer's premises, delivery at a country's port of entry, and delivery at end user level. The figures are months, banded by the product's total shelf life.

What the table is, and what it is not

The table carries one further band, for a total shelf life of 12 months or less. It has no figures at all, only the line that special arrangements and conditions apply.

Read the status of the document before using its numbers. It is titled Points to consider. Appendix 1 is headed as an example. The table's own caption says the figures rest on the outcome of a risk assessment. None of that makes the table unusable; it makes it a reference point rather than a limit.

Section 5.1 asks for remaining shelf life to be set realistically and adapted to each importer after a thorough risk assessment, taking account of the category and type of product, inventory level, manufacturing and transit lead time, local release lead time, storage conditions, the delivery chain, and resources in the recipient country or region. It also asks for agreements between suppliers, purchasers and recipients covering each party's responsibilities, including remaining shelf life or expiry date. The annex recommends that its content be considered for inclusion in national policy, which is an invitation rather than a rule already in force.

The table is also not new. This annex is an edit and republication of the same guidance issued as Annex 8 to Technical Report Series No. 1025 in 2020, with an appendix on emergency health kits added. The month figures in Appendix 1 are the same in both documents.

Why a percentage rule cannot reproduce the table

Some contracts state the requirement as a fraction of total shelf life instead: two-thirds remaining, or 85% remaining. A fraction and a fixed number of months are different tests, and they disagree in ways that depend on the product.

Working the port-of-entry column back into percentages shows why. Each band spans a range of total shelf lives, so one month figure represents a different fraction at each end of its band. The percentages below are arithmetic performed on the published months. They appear nowhere in the annex.

The step at each band boundary

Across the four bands the port-of-entry figure runs from roughly 29% to roughly 67% of total shelf life. No single percentage reproduces it. A two-thirds clause is stricter than the table almost everywhere in that range, and an 85% clause is stricter than it everywhere.

Banding also produces a step at every boundary. A product with a total shelf life of 36 months sits in the band asking for 15 months remaining at the port of entry. A product with 37 months sits in the band above it, which asks for 24. One month more total shelf life, nine months more on arrival. Where a product sits close to a boundary that step decides the outcome, and a percentage clause has no equivalent of it.

A worked example

Take a consignment of an oral solid product with a total shelf life of 36 months, manufactured in March and expiring 36 months later. It is delivered at the port of entry 14 months after manufacture, with 22 months remaining.

Against the annex, the product falls in the band above 24 and up to 36 months, where the example figure at port of entry is 15 months. Twenty-two months clears it, with seven months of margin.

Against a contract clause requiring two-thirds of total shelf life, the requirement is 24 months. Twenty-two months does not clear it. The consignment is two months short. Same batch, same arrival date, opposite answers, and neither test is wrong on its own terms.

Now change only the delivery point. If delivery in that contract means the end user rather than the port, the annex's figure for the band is 6 months, and the consignment has 16 months of slack in which to reach the end user. The number and the point it attaches to have to be agreed together.

• Fix the delivery point in the contract before the goods move: port of entry, in-country after customs clearance, or end user.
• Convert any percentage clause into months for the specific product before agreeing it, and check the result against the annex.
• Treat products whose total shelf life sits just below a band boundary as a separate case. The step at the boundary is large.

Retesting to extend a date

Section 5.3 is short and firm. Products with an expiry date should not be subjected to retesting by the purchaser or recipient for the purpose of extending shelf life. Only in exceptional cases, such as product shortages, should a recipient consider extending the expiry date of received batches, and then subject to conditions: available scientific data, the application of risk management principles, and approval from the national regulatory authority. The new expiry date should be reflected on the packaging.

Two things are allowed. Where a manufacturer or supplier has obtained approval from a national regulatory authority for a new or extended shelf life, that may be applied. And products with a retest date allocated by a manufacturer, such as chemicals and reagents, may be retested and used if the quality parameters are met.

That is the dating distinction doing its work again. An expiry date is a boundary the buyer cannot move on its own evidence. A retest date is a scheduled question the buyer can answer with a test.

Section 5.1 allows deviations from the policy to be negotiated between suppliers, recipients and national authorities where justified, on two conditions: that stock with a shorter remaining shelf life than the policy stipulates will be consumed before expiry, and that the product reaches end users with enough remaining shelf life to be confident there is time to use it. A deviation carries a consumption plan behind it. It is not an exception granted by asking.

What the certificate settles, and what it does not

The certificate of analysis supplies the inputs, not the answer. It carries the manufacturing date and the expiry or retest date, and total shelf life and the end point both follow from those. It knows nothing about when the goods will arrive, so remaining shelf life is arithmetic done at the border against a date the document cannot contain.

That makes the dates on the certificate worth checking before anyone computes anything from them. A missing manufacturing date is a request rather than a dead end: the annex notes that the manufacturing date should be defined by the manufacturer and provided if requested. A date that contradicts another date on the same document is a finding in itself, and a shelf life calculation built on it means nothing.

It is worth being plain about the annex's scope as well. It governs how much of a product's assured period should be left when the goods arrive. It says nothing about whether the batch met its specification when it was made. That question is answered by the results on the certificate, against the limits that apply to them.

Definitions

Remaining shelf life

WHO TRS 1044 Annex 8 glossary: the period remaining from the date of delivery to the expiry date, retest date, install-by date or other use-before date established by the manufacturer.

Shelf life

WHO TRS 1044 Annex 8 glossary: the period of time, from the date of manufacture, that a product is expected to remain within its approved product specification while handled and stored under defined conditions.

Upon delivery

WHO TRS 1044 Annex 8 glossary: the date a medical product is delivered as specified, for example at the port, at the point in-country after customs clearance, or at the end user, and as defined in the agreement between relevant parties.

Expiry date

WHO TRS 1044 Annex 8 glossary: the date placed on the container or labels of a medical product designating the time during which it is expected to remain within established shelf-life specifications if stored under defined conditions, and after which it should not be used.

Retest date

WHO TRS 1044 Annex 8 glossary: the date when a material should be re-examined to ensure that it is still suitable for use.

Sources

1. WHO Technical Report Series No. 1044 (2022), Annex 8: Points to consider for setting the remaining shelf-life of medical products upon delivery, World Health Organization (glossary, sections 5.1 to 5.3, and Appendix 1 Table 1)
2. WHO Technical Report Series No. 1025 (2020), Annex 8: Points to consider for setting the remaining shelf-life of medical products upon delivery, World Health Organization (Appendix 1 Table A8.1, the predecessor edition of the same table)

Primary sources are cited in preference to summaries. Where a source is licensed (for example a pharmacopoeial monograph) the reference is given and the text is not reproduced.

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