Glossary · Context
PREP Act
US federal law (2005) granting liability immunity for the development and deployment of medical countermeasures during a declared public health emergency.
The PREP Act (Public Readiness and Emergency Preparedness Act) is a US federal law from 2005 that allows the Health Secretary (HHS) to issue targeted declarations granting liability immunity to manufacturers, distributors and healthcare professionals for deploying medical countermeasures during a public health emergency. The goal: lift legal obstacles that would slow a rapid response to an epidemic threat.
The mechanism #
A PREP Act declaration is not a licence to ignore safety — it does not cover wilful misconduct or gross negligence. It simply recognises that, within a declared public health emergency, actors developing and administering countermeasures (drugs, devices, sometimes vaccines) must be able to act quickly without fear of being sued for foreseeable adverse effects. It has been activated for COVID-19, monkeypox and several other emergencies since 2005.
The Andes virus declaration of 24 May 2026 #
On 24 May 2026, HHS Secretary Robert F. Kennedy Jr. signed and had published in the Federal Register (document 2026-10539) a targeted declaration on the Andes virus. Three points to remember:
- Scope: the MV Hondius outbreak and its chain of transmission, not the Andes virus in general.
- Covered countermeasure: the investigational use of favipiravir, an RNA antiviral originally developed against influenza, as a potential treatment for hantavirus pulmonary syndrome.
- Duration: in force until 18 July 2026.
The declaration does not cover a vaccine and does not prejudge favipiravir's actual efficacy against the Andes virus — it only opens the way to framed compassionate use.
A measured read #
The declaration was publicly announced by RFK Jr. on his official @SecKennedy account the same day. For the bigger picture alongside the GPMB diagnosis on global preparedness, see our breakdown MV Hondius, a pandemic dress rehearsal.
Key figures
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2005
Year the PREP Act was passed by the US Congress. Authorises the Health Secretary (HHS) to issue 'targeted declarations' that activate liability protection.
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18 July 2026
Expiry date of the targeted PREP Act declaration on Andes virus signed by RFK Jr. (HHS Secretary, 24 May 2026), published in the Federal Register under number 2026-10539.
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Favipiravir
Medical countermeasure covered by the Andes virus declaration of 24 May 2026 — an RNA antiviral whose investigational use against hantavirus pulmonary syndrome is now PREP-Act-protected within the MV Hondius scope.
Standards & references
- ASPR — Public Readiness and Emergency Preparedness Act — Official page of the Administration for Strategic Preparedness and Response (HHS) on the PREP Act and active declarations.
- Federal Register — PREP Act Andes virus declaration (2026-10539) — Official text of the targeted Andes virus declaration, public inspection on 24 May 2026.
Frequently asked questions
What is the PREP Act?
The Public Readiness and Emergency Preparedness Act (PREP Act) is a US federal law passed in 2005 that allows the Health Secretary (HHS) to issue 'targeted declarations' granting liability immunity to manufacturers, distributors and healthcare professionals for the development and deployment of medical countermeasures (drugs, devices, vaccines) during a declared public health emergency. The idea: lift legal obstacles to enable a fast response.
How does it apply to the Andes virus?
On 24 May 2026, HHS Secretary Robert F. Kennedy Jr. signed a targeted declaration published in the Federal Register (document 2026-10539). It protects the investigational use of favipiravir (an RNA antiviral) as a potential treatment for hantavirus pulmonary syndrome, within the scope of the MV Hondius outbreak and its chain of transmission. The declaration is in force until 18 July 2026.
Does it cover an Andes vaccine?
No. The targeted declaration of 24 May 2026 covers only treatments (favipiravir as an investigational countermeasure). No vaccine is licensed against the Andes virus, and the PREP Act also does not prejudge favipiravir's actual efficacy against this strain — it only lifts liability barriers for experimental use.
Further reading
- PREP Act — ASPR / HHS page — ASPR / HHS (health authority page)
- Declaration under the Public Readiness and Emergency Preparedness Act for Medical Countermeasures against Andes Virus — Federal Register (document 2026-10539) (US federal document)