Pan American Health Organization · 2023
Guidance for healthcare workers on reading vaccine vial monitors (VVMs) to determine if vaccines have been damaged by heat exposure.
- Issuer
- Pan American Health Organization
- Edition
- 2023
- Audience
- Healthcare workers, immunisation programme staff, cold chain personnel
- Evidence
- Expert consensus and technical specifications
- Reviewed
- 17 Oct 2026 · GMJ
What this guideline says
GMJ summary
Vaccine vial monitors (VVMs) are heat-sensitive labels attached to vaccine vials that change colour irreversibly when vaccines are exposed to cumulative heat. The VVM consists of a square that gradually darkens from light to dark purple as heat exposure increases; when the square matches or exceeds the darkness of the surrounding reference circle (discard point), the vaccine must not be used. VVMs do not detect freezing damage.
There are five types of VVM (VVM2, VVM7, VVM11, VVM14, VVM30) designed to match different vaccine heat stabilities. Each type reaches its discard point at different rates depending on temperature exposure: for example, at 37 °C, VVM30 takes 30 days to reach discard point whilst VVM2 takes only 2 days. Three temperature classes (37 °C, 25 °C, 5 °C) are used to classify vaccine heat stability and assign the appropriate VVM type.
Healthcare workers should use vaccines with minimal colour change first for outreach sessions, prioritise vaccines showing more (but not discard-level) colour change before those with less change, and immediately report to supervisors when multiple vials reach discard point, which may indicate cold chain equipment malfunction or mishandling. The guideline emphasises that VVMs supplement, but do not replace, national temperature monitoring requirements.
Key points
For clinicians — doses and thresholds as stated in the guideline
- Use the vaccine if the VVM square is lighter than the outer reference circle; do not use if the square matches or is darker than the circle (discard point)
- Five VVM types exist: VVM30 (30 days to discard at 37 °C), VVM14 (14 days at 37 °C), VVM11 (11 days at 37 °C), VVM7 (7 days at 37 °C), and VVM2 (2 days at 37 °C)
- VVMs register cumulative heat exposure over time; higher temperatures cause more rapid colour change, which is irreversible
- VVMs do not detect freezing; they only respond to heat exposure above specified thresholds
- Vaccines should be stored under 8 °C according to manufacturer recommendations; VVMs do not immediately change colour with brief moderate heat exposure
- Select vaccines with minimal VVM colour change for outreach sessions; use vaccines showing more colour change (but not at discard point) before those with less change
- When multiple vials reach discard point, investigate cold chain equipment function, refrigerator thermometers, adequate ice pack use, and transport planning
- Healthcare workers who are colour-blind or have visual impairments should not be responsible for VVM interpretation decisions
Vaccine vial monitor (VVM) reaction rates by heat stability category and temperature exposure
Table extracted from the guideline
| VVM Type (Vaccine heat stability) | Maximum time to end point at 37 °C | Maximum time to end point at 25 °C | Time to end point at 5 °C |
|---|---|---|---|
| VVM30 (High stability) | 30 days | 193 days | ≥4 years |
| VVM14 (Medium stability) | 14 days | 90 days | ≥3 years |
| VVM11 (Intermediate stability) | 11 days | 71 days | ≥2.5 years |
| VVM7 (Moderate stability) | 7 days | 45 days | ≥2 years |
| VVM2 (Least stable) | 2 days | 225 days at 25 °C | Not applicable |
Source: Pan American Health Organization, Guidelines for healthcare workers on the proper interpretation of vaccine vial monitors and their use. Reproduced in summary form.
From the guideline
Verbatim
“The VVM is a heat indicator that is triggered by a temperature rise above a specified threshold. Therefore, any change in the color of the VVM indicates that the vaccine vial has been exposed to high temperatures for an undetermined amount of time.”
Editor’s perspective
Why this matters for Georgia and the region
Prof. Giorgi Pkhakadze, MD, MPH, PhD
Editor-in-Chief, Georgian Medical Journal · Chair, Public Health Institute of Georgia · WHO consultant, health and migration
As Chair of Georgia's Public Health Institute and having worked with immunisation programmes across the region, I recognise that VVMs are particularly valuable for our context where peripheral health facilities face electricity interruptions and mobile teams traverse challenging geography from Adjara to Tusheti. The guidance on prioritising partially heat-exposed vaccines (not yet at discard point) before less-exposed ones is operationally important and counters the traditional 'first in, first out' approach. For Georgian health workers, I would emphasise the distinction between the five VVM types: understanding that hepatitis B vaccine (VVM30, stable for 176 days at 25 °C) tolerates heat far better than OPV (20 days at 20 °C) helps staff plan outreach logistics appropriately. The critical implementation challenge is that this guidance explicitly states PAHO has not issued a formal policy statement on VVM use and instructs programmes to continue following national norms on continuous temperature monitoring as the primary standard—so VVMs remain supplementary tools, not replacements for electronic temperature loggers that Georgia's immunisation programme has been deploying under GAVI support since 2016.
ORCID 0000-0001-7609-4515 · Perspective written for the GMJ Guidelines Library, 17 Oct 2026
Applicability
Georgia and the South Caucasus
For Georgia and countries in the South Caucasus and Eastern Europe, this guidance is directly applicable to national immunisation programmes using WHO-prequalified vaccines with VVMs. National programmes must integrate VVM interpretation into existing cold chain monitoring protocols, particularly important given variable electricity supply in rural areas and during transport across mountainous terrain. Training should extend to peripheral health facilities and mobile vaccination teams conducting outreach in remote regions. Programmes should establish information systems to collect and report VVM colour changes as indicators of cold chain integrity, whilst continuing to use continuous temperature monitoring devices as the primary standard. Health workers require training to distinguish VVM colour changes, with alternative supervision arrangements for colour-blind staff.
Questions this guideline answers
Quick answers
Can I still use a vaccine if the VVM has changed colour but hasn't reached the discard point?
Yes. As long as the VVM square is lighter than the outer reference circle, the vaccine can still be used. In fact, vaccines showing some colour change (but not at discard point) should be used before vaccines with less colour change.
Does the VVM tell me if a vaccine has been frozen?
No. VVMs are not affected by freezing temperatures and cannot provide information about freeze damage. They only detect heat exposure above specified thresholds.
How many times can I take an unopened vaccine vial with a VVM on outreach sessions?
There is no limit to the number of times, as long as the VVM square has not darkened to match the reference circle. The VVM indicates cumulative heat exposure regardless of how many trips the vial has made.
What should I do if I find multiple vaccine vials have reached the VVM discard point?
Keep the vaccines refrigerated, do not use them, and immediately inform your supervisor. Document the lot numbers, expiry dates, and investigate possible causes: refrigerator malfunction, thermometer problems, insufficient ice packs, or transport delays. This may indicate a cold chain failure requiring corrective action.
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- Issuer
- Pan American Health Organization
- Type
- Procedures, manuals, guidelines
- Edition
- 2023
- Status
- Current
- Published
- 2023-01-01
- Scope
- Vaccine cold chain management
- Audience
- Healthcare workers, immunisation programme staff, cold chain personnel
- Licence
- CC BY-NC-SA 3.0 IGO
- Evidence
- Expert consensus and technical specifications
- Record history
- Created 17 Oct 2026 · updated 17 Oct 2026 · next check Apr 2027
Pan American Health Organization. Guidelines for healthcare workers on the proper interpretation of vaccine vial monitors and their use. Washington, D.C.: PAHO; 2023. (PAHO/CIM/23-0012).GMJ Guidelines Library records are original summaries written by the GMJ editorial team from the issuer’s published document and reviewed by a physician. They do not replace the full guideline. The document is the copyright of its issuer and is linked, not hosted. Spotted an error or a newer edition? Tell the Guidelines Desk.
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