Establishing a COVID‐19 pandemic severity assessment surveillance system in Ireland

Abstract We developed a COVID‐19 pandemic severity assessment (PSA) monitoring system in Ireland, in order to inform and improve public health preparedness, response and recovery. The system based on the World Health Organization (WHO) Pandemic Influenza Severity Assessment (PISA) project included a panel of surveillance parameters for the following indicators: transmissibility, impact and disease severity. Age‐specific thresholds were established for each parameter and data visualised using heat maps. The findings from the first pandemic wave in Ireland have shown that the WHO PISA system can be adapted for COVID‐19, providing a standardised tool for early warning and monitoring pandemic severity.


| INTRODUCTION
Pandemic severity assessments (PSAs) provide information to determine the timing, scale and intensity of pandemics and to support decisions on the urgency of pandemic response actions and on implementing and lifting control measures. [1][2][3] In the absence of a society (e.g., excess mortality) and the health-care sector (e.g., hospitalisations). 2 Following the declaration of the COVID-19 pandemic on the 11 March 2020, 4 we aimed to develop and implement a PSA monitoring system in Ireland, in order to inform public health preparedness, response and recovery measures, and to assist in improving the response to future waves of COVID-19.

| METHODS
A series of surveillance parameters for each indicator was identified and analysed by age group (0-14, 15-64 and ≥65 years), overall and week (Table 1). Threshold levels for each parameter were developed (by age group, overall and week) and applied to datasets from the first COVID-19 wave (March-June 2020) in Ireland.
Age-specific statistical thresholds for transmissibility and impact parameters (baseline to extraordinary) were calculated using the Moving Epidemic Method based on historical data (previous 5 years). 5

| Impact
The impact of the COVID-19 pandemic during the first wave  which would enhance data interpretation, in particular with limitations of available historical data for threshold calculation. There was a lower level of confidence in data reported during the initial weeks of the pandemic, due to the rapid evolution of the situation and frequent changes to testing capacity, criteria for testing and case definitions.

| Seriousness of disease
Our study provided an epidemiological description and assessment of the severity of the first COVID-19 pandemic wave in Ireland.
The heat maps were easily understood, concurred with the epidemiological situation and were reported to the National Public Health Emergency team. This PSA system will be used going forward in conjunction with enhanced surveillance data, 9,10 to monitor COVID-19 activity in Ireland. We believe this is a useful surveillance tool to inform and guide national decisions and recommendations on public health interventions and for guiding control measures in Ireland as we move through pandemic waves. We have shown that the WHO PISA system can be adapted for COVID-19 in Ireland (and possibly other pathogens with pandemic potential), providing a standardised tool to monitor pandemic severity and for early warning for current and future pandemic waves. Syndromic surveillance data are effective and timely when assessing pandemic severity, particularly when testing capacity may change and for monitoring novel respiratory pathogens (with no existing microbiological tests).
We recommend that PSAs, using this PSA system, be conducted regularly in Ireland as the pandemic progresses. We also recommend that other transmissibility measures such as reproductive numbers are considered for integration into the WHO PISA framework in the future. Current and future applications of this PSA system in Ireland include monitoring the impact of the COVID-19 vaccination programme, 11,12 the changing epidemiology due to SARS-CoV-2 variants of concern 13 and monitoring both SARS-CoV-2 and influenza each winter.

CONFLICT OF INTEREST
The authors have no conflicts of interest to declare that are relevant to the content of this article.

ETHICS APPROVAL
Not required; aggregated anonymised routine surveillance data were used in this study.

CONSENT TO PARTICIPATE
Not required; aggregated anonymised routine surveillance data were used in this study.

CONSENT FOR PUBLICATION
Not applicable.

CODE AVAILABILITY
Not applicable.

PEER REVIEW
The peer review history for this article is available at https://publons. com/publon/10.1111/irv.12890.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author, upon reasonable request.