Vulnerable-person registry with scripted phone check-ins during alerts, opt-out by default

Mechanism

Four components working as one chain:

1. A registry of residents at elevated heat risk (isolated elderly people, people with disabilities or chronic illness), maintained by the city or its social-action agency.
2. A call center activated when the heat alert level is reached, with rotating agents phoning every registrant on a fixed cadence for the duration of the alert.
3. A clinician-designed triage script so that non-medical agents can reliably detect early signs of heat illness and give correct advice (hydration, cooling, when to seek care).
4. Escalation to in-person checks (social workers, emergency services) when a registrant cannot be reached or the script flags danger.

Where it fits

City scale, run by municipal social services. It targets the population that dominates heatwave mortality: isolated people aged 75 and over, who are largely invisible to alert broadcasts and will not travel to cooling centers. It converts a passive warning system into active outreach.

Evidence

France created mandatory communal registries after the 2003 heatwave (14,802 deaths, roughly 82% aged 75 and over). The registry, as part of the wider national heat plan, is credited with a large share of the mortality reduction in the 2006 heatwave (an estimated 4,000+ avoided deaths nationally vs. 2003-based expectations, Fouillet et al. 2008). 2019 record heat produced about 90% lower excess mortality than 2003.

The key design finding: opt-in registries capture only about 10% of eligible people. Paris has only ~7,500 registrants despite decades of promotion. France's July 2026 decree switches to opt-out auto-enrollment through welfare data-matching, expected to cover about 2 million isolated elderly people, following consultations with the CNIL data-protection authority.

Implementation path

1. Establish the legal basis for the registry and, where possible, opt-out enrollment using existing welfare or pension data, with data-protection review.
2. Write the triage script with hospital clinicians or geriatricians, not communications staff.
3. Staff a rotating call pool sized to the registry (Paris: ~40 agents handling up to 400 calls/day, each registrant reached every 2 days during a level-3 alert).
4. Define escalation rules and connect them to social services and emergency response.
5. Test the chain annually before summer.

Trade-offs

• Under opt-in rules, decades of outreach still leave roughly 90% of eligible people off the register; the intervention protects a small, self-selected fraction unless enrollment is flipped to opt-out.
• Opt-out data-matching raises privacy questions and requires data-protection authority involvement (France ran CNIL consultations before its 2026 decree).
• Call capacity must scale with the registry: an auto-enrolled register of millions cannot be served by staffing designed for thousands, so triage tiers or automated first-pass calls become necessary.
• Phone contact misses people without phones or with hearing or cognitive impairments; the in-person escalation layer is not optional.