Published in PLOS One on 2026-06-18, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Hana Rohan, Aaron F Bochner, Lauren Brown, Elizabeth M Ortiz, Amanda McClelland
Source: PLOS One • DOI 10.1371/journal.pone.0351209
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
During the COVID-19 pandemic, Alert Level Systems (ALS) were widely implemented as public health tools to communicate risk levels and recommend public health and social measures (PHSMs). However, the efficacy of ALS in mitigating disease spread and their impact on public health responses have not been systematically evaluated. This study aims to assess perceptions of ALS implementation across diverse jurisdictions and derive lessons for future public health emergencies.
Key informant interviews were conducted remotely between December 2023 and March 2024 with senior stakeholders who were involved in ALS development and implementation during the COVID-19 pandemic, from eight jurisdictions: California (US), New Zealand, the Philippines, Rio Grande do Sul (Brazil), Singapore, South Africa, the United Kingdom, and the United States. A thematic analysis approach was applied to synthesize insights, focusing on the strengths, challenges, and key lessons from ALS implementation.
ALS were generally perceived by key informants as useful tools for communicating risk and supporting adherence to PHSMs due to their simplicity and transparency. However, significant challenges were identified, including difficulties in accessing reliable data, lack of clear ALS objectives, and insufficient community engagement. The study highlights the need for ALS to integrate social, economic, and epidemiological data in decision-making processes. Jurisdictions also reported that pre-existing ALS governance structures and stronger community feedback mechanisms could have improved implementation outcomes.
ALS can serve as valuable public health communication tools in future epidemics, but their success depends on clear objectives, evidence-based PHSMs, and robust community engagement. Pre-emptive development of ALS structures and governance will improve preparedness for future epidemics. Transparent and flexible decision-making processes will be crucial for sustaining public trust.
Introduction
During public health emergencies, it is typically necessary to communicate to the public changing levels of risk, along with recommended public health and social measures (PHSMs) to mitigate these risks. Alert Level Systems (ALS) are an emergency preparedness and response tool, often including colour-coded and/or numbered levels, used to centralize and simplify communication to inform individuals, communities, organizations, and/or decision-makers of their current risk of a particular hazard.
ALS were widely used during the COVID-19 pandemic both to communicate risk and translate policy into recommended actions, [1–7] and to facilitate internal assessments of risk by decision-makers. COVID-19 ALS were usually linked to recommended or mandated measures to reduce or mitigate transmission risk. As risk heightened, alert levels increased, and guidance or measures increased in stringency and number; as risk abated, levels decreased and measures were relaxed. [8] COVID-19 ALS typically relied on data produced by surveillance systems to underpin assessments of risks, set alert levels, and help assign appropriate PHSMs and other interventions.
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider public health desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Hana Rohan, Aaron F Bochner, Lauren Brown, Elizabeth M Ortiz, Amanda McClelland. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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