WHO PQS Pre-Qualification: Vaccine Data Logger Spec Guide

WHO PQS Pre-Qualification: The Spec Sheet Behind Every Vaccine-Grade Data Logger

If your data logger is destined for a vaccine refrigerator, a UNICEF tender, or a Gavi-funded immunisation program, one acronym decides everything: PQS. The World Health Organisation's Performance, Quality and Safety pre-qualification scheme dictates the exact specifications a temperature monitoring device must meet before it can be procured for the global vaccine cold chain. Miss a single line in that spec, and the device is locked out of the largest immunisation buyer base on the planet. This guide breaks down the PQS requirements for vaccine data loggers, maps them to specific Ideabytes models such as the IBI-MTH120, IBI-WTH50, and IBI-MTH70, and gives buyers a clean checklist they can use during procurement.

What WHO PQS Actually Is

WHO PQS is run by the Immunisation Devices and Equipment unit at the World Health Organisation. It maintains a public catalogue of products that have been independently type-tested and verified to meet WHO's published performance specifications. For temperature monitoring, the relevant umbrella category is E006: Temperature monitoring devices, which covers thermometers, freeze indicators, electronic recorders, data loggers, Equipment Monitoring Devices (EMDs), and event loggers used at every level of the cold chain. Within E006, several sub-categories define the exact device class: TR for temperature recorders and electronic loggers, RF for refrigerator monitors, IN for in-transit and vial-level indicators, and DL for data loggers with a machine-to-machine (M2M) interface.

A 2023 update to the framework introduced the WHO Equipment Monitoring System (EMS) tiers. Level 1 is an integrated logger with USB and M2M ports. Level 2 adds a local display. Level 3 adds remote communications such as GSM, cellular SIM, or Wi-Fi. The policy direction is firm: from 2024 every new vaccine refrigerator must include an EMS, and from 2026 every vaccine refrigerator in service must have one. That timeline is what is driving the current spec scrutiny in healthcare procurement teams.

The Functional Specs Your Logger Must Hit

The verification protocol that buyers most often quote is WHO/PQS/E006/TR06.VP.4, dated 12 May 2022, which governs the 30-day electronic refrigerator temperature logger. It is the most prescriptive document in the family, and it sets the reference bar that other E006 device classes are measured against. The non-negotiables are:

• Accuracy of ± 0.5°C across the full operating range.

• Operating temperature span of -25°C to +55°C, so the device survives both deep freezer adjacency and tropical ambient.

• Minimum logging interval of one minute, with a continuous 30-day rolling buffer that overwrites the oldest data.

• Visual alarm display showing 30 days of OK / ALARM status with a daily min and max history mode.

• Battery life of at least two years from activation, using a non-replaceable lithium coin cell.

• Ingress protection rating of IP64.

• Heat alarm above +8°C and freeze alarm at -0.5°C (the Type C freeze-sensitive configuration), reflecting the WHO and UNICEF storage band of +2 °C to +8 °C with freeze prevention prioritised because vaccines such as DTP, HepB, and HPV lose potency once frozen.

PQS Vaccine Data Logger Spec Checklist

Use the table below as a procurement filter. If a vendor cannot tick every row in writing, the device is not ready for a UNICEF or Gavi-funded program.

How Ideabytes Loggers Map to E006 Use Cases

Ideabytes data loggers are engineered around the same accuracy, alarm, and connectivity envelope that PQS calls for. While each program must run its own verification, the following models cover the three connectivity tiers that buyers most frequently specify.

• IBI-MTH120 - 4G M2M Temperature and Humidity Data Logger. Built for EMS Level 3 remote-monitoring deployments. It uses 4G LTE CAT1 with an in-built M2M SIM, achieves +/- 0.5°C accuracy in the -10°C to +50°C band that includes the entire +2 to +8 vaccine zone, and has a measuring range from -40°C to +120°C. Compliance covers FDA 21 CFR Part 11, CE, FCC, and IC, and the unit is suited to pharmaceutical storage monitoring and healthcare facility compliance.

• IBI-WTH50 - Wi-Fi Built-In Temperature and Humidity Data Logger. Targets vaccine refrigerators that already sit on a facility Wi-Fi network. Connectivity is Wi-Fi 802.11 b/g/n on 2.4 GHz, accuracy is +/- 0.5°C in the -10°C to +50°C band, and the measuring range of 0 °C to +50 °C with humidity from 0% RH to 100% RH directly brackets the WHO +2 to +8 storage window plus the wider room-temperature pharmacy zone.

• IBI-MTH70 - 4G M2M Temperature and Humidity Data Logger. Designed for in-transit cold chain shipments and last-mile clinics where Wi-Fi is unreliable. Connectivity is 4G LTE Cat1 with 2G fallback, accuracy is +/- 0.5°C in the -10°C to +50°C band, and the measuring range of -20°C to +70°C with humidity 0% to 99% RH non-condensing fits both refrigerated transport and ambient secondary packaging.

Calibration, Traceability, and Why ISO 17025 Is Non-Negotiable

WHO will not accept calibration data from any laboratory that lacks ISO/IEC 17025 accreditation issued by a body that is a signatory to the International Laboratory Accreditation Cooperation (ILAC) Mutual Recognition Arrangement, layered on top of an ISO 9001 quality management system. Each prequalified device must ship with a calibration certificate whose uncertainty is traceable through that 17025 chain back to a national metrology institute. Verification protocols such as E006/TR06-VP.4 and E006/DL01-VP.2 specify the exact accuracy, drift, and stability tests the laboratory must run before WHO will even open the dossier.

For procurement teams, this means two things. First, ask the manufacturer for a sample certificate of calibration on the actual model, not on a sister product. Second, confirm the issuing lab's accreditation number on the ILAC public register. A logger that meets every functional spec but ships with a non-17025 certificate is still ineligible for PQS listing.

The Pre-Qualification Process, End to End

The WHO IMD-PQS workflow has six predictable stages. First, the manufacturer submits an application and full technical dossier through the WHO ePQS system, including QMS evidence and manufacturing documentation. Second, an independent ISO/IEC 17025 laboratory runs type-testing using the verification protocol that matches the device class. Third, the test report and the manufacturer's compliance dossier are returned to WHO. Fourth, WHO performs a desk review of both. Fifth, on approval, the device is listed in the public PQS catalogue and on the IMD Listing Products E006 page, which is what makes it visible to UNICEF Supply Division and Gavi-funded buyers. Sixth, ongoing surveillance kicks in, including audits, complaint handling, and re-testing whenever the spec is revised.

Where this trips programs up is in the surveillance stage. A firmware change, a sensor part substitution, or a battery chemistry tweak can all trigger a re-test. Buyers should ask vendors for a documented change-control process aligned with the original PQS dossier.

VVMs and Electronic Loggers Work Together, Not Against Each Other

One question that surfaces in every cold chain audit is whether a Vaccine Vial Monitor (VVM) replaces an electronic logger. It does not. The VVM, defined under WHO/PQS/E006/IN05.4, is a chemical heat-sensitive label applied to the vial that darkens cumulatively with cumulative time-temperature exposure. It is the last-mile evidence that survives even after the cold chain ends at the point of use. Electronic loggers like the IBI-MTH120, IBI-WTH50, and IBI-MTH70 capture the active monitoring layer up to that point, with timestamped data, alarm history, and remote alerts. A best-practice deployment uses both: VVMs on every vial, electronic loggers in every refrigerator and shipper.

What Happens If Your Logger Is Not PQS-Aligned

The cost of a non-aligned logger is not just procurement risk. UNICEF and Gavi tenders explicitly require PQS-listed products, so a non-listed device blocks access to the largest single buyer for vaccines worldwide. National regulators that mirror WHO guidance will fail data quality assessments (DQA) when audit logs come from a non-traceable device. Insurance and reinsurance carriers underwriting vaccine shipments increasingly demand PQS-equivalent monitoring records. The downstream cost of a 2,000 dollar logger that is one spec line off can be a six-figure rejected shipment.

Buyer's Checklist Before You Sign the PO

Before issuing a purchase order for a vaccine-grade data logger, walk through this short list with the vendor:

1. Confirm the PQS device class the model targets (TR, RF, IN, or DL).

2. Request the verification protocol report from an ISO/IEC 17025 accredited lab.

3. Verify accuracy of +/- 0.5°C across the full operating temperature.

4. Confirm the alarm configuration matches Type C (heat above +8, freeze at -0.5).

5. Check the EMS tier (Level 1, 2, or 3) against your remote-monitoring requirement.

6. Inspect the calibration certificate for ILAC MRA traceability.

7. Confirm IP64 ingress protection and battery life of at least two years.

8. Ask for a documented change-control policy aligned with PQS surveillance.

Conclusion

WHO PQS is not paperwork. It is the contract that decides whether a logger can be deployed in a national immunisation program or a Gavi-funded clinic in 2026 and beyond. The spec is precise, the calibration chain is non-negotiable, and the EMS Level 3 mandate is on the calendar. Ideabytes models such as the IBI-MTH120 for cellular remote monitoring, the IBI-WTH50 for facility Wi-Fi deployments, and the IBI-MTH70 for in-transit cold chain shipments are engineered around the same accuracy, alarm, and connectivity envelope that PQS verification demands. If you are scoping a vaccine cold chain refresh, start with the checklist above, get the calibration evidence in writing, and align your procurement with the EMS framework before the 2026 deadline turns into an audit finding.