Tiered public health and social measures (PHSM) systems are a core component of effective COVID-19 preparedness, response and risk communication. These systems use indicators of disease spread to determine the appropriate level of PHSMs at a given time and in a given place, informing targeted interventions that are appropriate for different levels of disease transmission. These systems empower the public to stay safe by keeping people informed about the risk of COVID-19 in their area. If designed and implemented effectively, a tiered PHSM system can help national decision-makers reduce SARS-CoV-2 transmission and save lives while avoiding the implementation of PHSMs that are unnecessarily harsh or disruptive socially and/or economically. Finding this balance is crucial in the ongoing fight against COVID-19.
As of May 2021, few African Union (AU) Member States have implemented tiered PHSM or alert-level systems for COVID-19 at the national level to guide PHSM implementation (Appendix C); these efforts do not address regional or continental level situational awareness. The Partnership for Evidence-Based Response for COVID-19 (PERC) has developed a continent-level dashboard to provide this situational awareness.
This document describes the continent-level PHSM dashboard and explains how this framework can be adapted to a national COVID-19 tiered PHSM system.
At the continent-wide level, the PERC dashboard uses a four-tiered COVID-19 PHSM system. This number of tiers allows adequate targeting of PHSMs to disease transmission levels while avoiding overly complex messaging. To determine the PHSM tier, we use two core indicators that illustrate the burden of COVID-19 within a nation. The overall PHSM tier for each Member State is set by the higher of the two proposed core indicators, each of which is correlated with the amount of COVID-19 transmission within a region at a specific time.
|Core Indicators||Tier 0 No data available||Tier 1 Standard precautions||Tier 2 Low alert||Tier 3 Moderate alert||Tier 4 High alert|
|Daily case incidence (new cases per 1M people per day, 7 day average)||n/a||<5||5- <20||20 - <80||≥80|
|Test positivity rate (last 14 days)1,2||n/a||<3%||3% - <5%||5% - <12%||≥12%|
|If data is available: The percentage of hospital beds occupied by COVID-19 patients3||n/a||n/a||n/a||n/a||≥20%|
1. This includes both antigen and PCR tests as described by the WHO case definition and Africa CDC guidelines.
2. We presented this indicator as percent positivity, to be consistent with WHO guidance. If a Member State prefers, it can present an equivalent indicator using the test-to-case ratio with the following thresholds: >33.3, 33.3 to >20, 20 to >8.3, and ≤8.3.
3. This indicator is not included in the PHSM Tiers Dashboard because the data is not readily available in a timely manner for most Member States.
The first core indicator, daily case incidence is a measure of COVID-19 spread within a community. This indicator’s validity is dependent on a country’s ability to test and diagnose individuals with COVID-19. In settings where the population has inadequate access to testing, most infected individuals may go undiagnosed; therefore, this indicator may dramatically underestimate the true infection prevalence, resulting in a low case-to-infection ratio. The performance of this indicator may be sub-optimal in countries with low testing rates per capita. Although there is no specific testing target because testing volume should vary at different stages of the pandemic, for the week of 26 April to 2 May 2021, the median testing rate across Member States was 837 tests/1M/week. Member States with much higher or lower testing rates may benefit from threshold adjustments when tailoring daily case incidence thresholds to a specific country context.
We use test positivity as a second core indicator because this value will increase as testing strategies change to more specific case definitions when testing capacity is overwhelmed. The accuracy of daily case incidence as an indicator of infection burden can vary depending on the epidemic situation. For example, when COVID-19 testing capacity is overwhelmed by a surge of cases, case counts are more likely to be significant underestimates of the true numbers of infections. In times when testing capacity is stretched, testing strategies may shift to prioritize testing only symptomatic or hospitalized individuals. This may cause an increasing proportion of infections to go undiagnosed, especially mild and asymptomatic infections. Thus, we use test positivity as a second core indicator.
The thresholds for these indicators were determined by reviewing data for all Member States through March 2021. We attempted to set thresholds that could be applied to all Member States, such that Member States would be at Tier 1 when experiencing low levels of transmission and be at Tier 4 when experiencing high levels of transmission, but before hospital capacity is overwhelmed. However, due to differences in testing strategies and capacities between Member States, there was no single set of thresholds that performed optimally for all Member States. Thus, Member States should review the performance of proposed thresholds for their specific context and adjust them as necessary. And once thresholds have been set, Member States should assess the performance of their thresholds over time, as testing capacity and factors contributing to disease spread (such as new variants) continue to change.
While the PHSM tier dashboard includes only two core indicators, if the data are available we recommend that countries add a third core indicator based on the percentage of hospital beds occupied. When this indicator shows that hospitals are approaching capacity, we recommend that it trigger the most restrictive PHSMs – Tier 4. The exact indicator and thresholds may vary based on data available for the Member State, but could include >20% of all hospital beds occupied by COVID-19 cases to trigger Tier 4. It is up to the discretion of each Member State to determine if they would use a hospital capacity indicator to trigger all PHSM tiers or only Tier 4. This decision can be made by reviewing historical data to assess how hospital capacity changed during previous COVID-19 waves. The main objective is for this indicator to trigger Tier 4 approximately 4-6 weeks before hospitals would become overwhelmed, which would allow time for Tier 4 PHSMs to “bend the curve” and prevent a scenario where patient care is compromised by an overwhelmed health care system.
We recognize that the quality of data on daily case incidence, test positivity and hospital capacity varies across Member States. Considering their specific context, data quality and data availability, Member States may choose to include other core indicators in their tiered PHSM system. For example, death rates could be used to trigger changes in PHSM tiers (this PHSM system does not incorporate deaths because it is a lagging indicator, typically behind cases by two to three weeks).
In this framework, changes in PHSM tier, whether up or down, are determined by data. The prompt to change from one tier to another is a core indicator crossing a pre-specified threshold. Each proposed PHSM tier should link to clear guidance on which activities are permitted and restricted at that level and which PHSMs should be adopted. A simple, clear infographic is the ideal way to communicate this information (Appendix A). The recommendations at each tier should be based on existing scientific evidence around which activities increase risk of COVID-19 spread, and which PHSMs decrease risk (Appendix B). Our framework includes an example of how PHSMs can be assigned at each tier; this guidance can be adapted to fit each Member State’s local context. Member States may also decide to implement different PHSMs in different settings. For example, rural and urban areas may implement different restrictions at the same tier if their primary venues for COVID-19 transmission vary.
As vaccination coverage increases, Member States may consider implementing individualized PHSMs that vary based on vaccination status. If this approach may be applicable to Member States’ country context, more information is available from WHO. In addition, with the emergence of more infectious COVID-19 variants, it remains critical that everyone continue to wear a mask and socially distance when possible to decrease transmission, regardless of vaccination status, especially when incidence rates are elevated.
In this dashboard, the overall PHSM tier for each Member State is determined by the higher of the two proposed core indicators. However, when implementing at country level, the ultimate decision to change tiers should be made by a multi-sectoral advisory group. When an indicator crosses a pre-specified threshold, this group should meet and review the disease situation, including the presence of variants of concern, mortality rates per capita, weekly trends in incidence rates, weekly trends in death rates, and health system capacities such as available oxygen supply. Additionally, the advisory group should go beyond health indicators and assess the economic, political and social context, considering societal elements that may be affected by a PHSM tier change. Member States may define a set of secondary indicators that provide information about the outbreak situation, such as health care system, health care worker infections, disease control capacity, economic impact and social harm to inform this decision. The advisory group can agree to change PHSM tiers or to defer the change and provide a revised set of conditions for when a change should occur. Decisions should be made with local community input.
To avoid confusing the public and to allow sufficient time for PHSMs to impact COVID-19 transmission, PHSM tier changes should not occur more than once every two weeks, though Member States may be forced to increase tiers more frequently during a rapid surge in cases. When decreasing tiers, ideally changes are made even less frequently, to avoid a possible resurgence of cases, though detrimental secondary impacts of PHSMs must be taken into account. In some cases, ascending more than one tier may be necessary (although threshold differences between tiers should be broad enough to make this uncommon). For example, if a Member State is at Tier 2 but hospitals experience a sudden large increase in COVID-19 cases, ascension to Tier 4 may be necessary.
The dashboard assigns a single PHSM tier to each Member State, providing an overall estimate of the current outbreak severity in each country and indicating the types of PHSMs that may be appropriate. However, for Member States choosing to adopt their own national tiered PHSM systems, assigning tiers at the subnational level may be more appropriate, depending on the size and population of the country. Assigning PHSM tiers at the subnational level may permit more precise targeting of PHSMs to the areas facing high levels of COVID-19 transmission. However, overly granular implementation should be avoided where testing numbers are low, as this can lead to unstable and inaccurate estimates of COVID-19 disease spread. Evaluating the performance of the tiered PHSM system using historical data can inform decisions around the appropriate level of geographic granularity for a specific setting; caution is warranted when applying these indicators to regions reporting fewer than 100 tests per week. Applying the PHSM system to regions with inadequate test data can lead to imprecise estimates of the core indicators, resulting in shifts in PHSM tiers that do not track true transmission levels.
A national tiered PHSM framework developed and implemented using the best practices described in this framework can help keep communities healthy and safe while minimizing social and economic disruption. A tiered PHSM system can allow economically and socially important activities to continue while the epidemic is under control, resorting to stronger measures only when necessary. PHSM measures should be evidence-based, geographically targeted, protective of the health care system and supportive of the most vulnerable populations. If designed well and implemented consistently, systems can empower officials to communicate effectively with constituents, guide communities through a cohesive response strategy, build public trust and encourage community support of necessary preventive measures. This will limit both the economic and health damage of COVID-19.
© 2021 Africa CDC