key: cord-0808639-3xx24ado authors: Adlhoch, Cornelia; Gomes, Helena de Carvalho title: Sustainability of surveillance systems for SARS-CoV-2 date: 2022-04-22 journal: Lancet Infect Dis DOI: 10.1016/s1473-3099(22)00174-8 sha: 8e90716ca8fce9face7812554afef36a2c08f6f1 doc_id: 808639 cord_uid: 3xx24ado nan Vaccines, variations in surveillance systems, virus testing, and a mix of measures to protect vulnerable groups keep SARS-CoV-2 case numbers at bay and avoid overburdening health systems. This process can be complex. Whenever a new variant of SARS-CoV-2 emerges and is of concern, the scientific community races to understand its characteristics. Is this variant less or more transmissible? Can this variant evade immune responses to previous infection or vaccination? Does this variant cause less or more severe disease? Who is mostly affected, and which (sub)population is at the highest risk? These crucial parameters help estimate immediate response options and future responses and health-care needs. Observational population-based data from different monitoring systems are the first available information to generate such evidence. Despite limitations, realtime and comprehensive surveillance data allow rapid assessment of the situation of any disease, during a pandemic or otherwise, underlined in the two country data analyses from Denmark and Scotland published in the The Lancet Infectious Diseases by Peter Bager and colleagues 1 and Aziz Sheikh and colleauges, 2 respectively. Both studies assess the risk of hospitalisation as a proxy for the severity of the SARS-CoV-2 omicron variant (B.1.1.529) by combining surveillance data across different health-care levels with mortality data and information on vaccination. Both Denmark and Scotland rely on comprehensive data collection, which includes case-based data on outpatients and inpatients with confirmed SARS-CoV-2 infection, accompanied by detailed information about the patients, such as comorbidities, immunosuppression, previous SARS-CoV-2 infection, and vaccinations against COVID-19, as well as confirmation of the infecting variant virus through S-gene dropout analysis or variantspecific PCR, supplemented by extensive whole-genome sequencing programmes. There are many challenges when investigating the severity of a newly emerging virus or virus variant. Over the course of the pandemic, younger age groups were infected before the virus reached older more at-risk populations, which influences the severity assessment over time. Both studies 1,2 used hospitalisation as a proxy of severity, covered a relatively early phase of the omicron wave, and had a short follow-up period, which could lead to underestimation of the true severity of the omicron variant. In both studies, 1,2 the rapid spread of the omicron variant within the population, with more than 150 000 cases in both studies over a very short period, provided the basis for robust analyses. Cox proportional hazards and log-linear Poisson regression approaches resulted in similar results, with risk ratios (RRs) of 0·32 (95% CI 0·19-0·52) 2 and 0·29 (0·21-0·39), 1 respectively, supporting results from South Africa 3-5 and the UK 6 of a lower risk of omicron causing severe disease requiring hospitalisation. The studies showed that the booster vaccine dose was associated with a 57% (54-60) reduction in the risk of symptomatic S-gene-negative infection relative to 25 weeks or more after the second vaccine dose, 2 and a RR for hospitalisation of 0·50 (95% CI 0·32-0·76) among those who received three vaccine doses. 1 High-quality data from various geographically different countries are of utmost importance in an international context for regional or global assessments. Tremendous efforts and investments into different surveillance systems have been made during the COVID-19 pandemic to enhance testing and genotyping capacity, data linking, and reporting. Both studies discussed here 1,2 show that it is crucial to have solid data links between epidemiological and virological information in a timely manner. How long will countries be able to keep such comprehensive systems active for SARS-CoV-2 surveillance? Many countries in Europe are already reducing testing availability and limiting sequencing for various reasons, including availability of resources, as also already indicated in the Danish study. 1 How can we ensure that we will be able to identify, track, and assess the epidemiological situation for SARS-CoV-2, including new variants, with less comprehensive systems? Surveillance systems, testing, and sequencing efforts need to be representative and targeted, interlinked, robust, and detailed enough to establish rapid evidence for a situation overview. The balance between specific or marker PCRs accompanied by the right level of full genomic data needs to be found for the best cost-effectiveness and system sustainability. a Flickr/NIAID Expanding such a system to include diseases other than COVID-19 could benefit public health as a whole. It is important to define the type and level of detail needed for data on a local, national, regional, and global level to be prepared for the next SARS-CoV-2 variant and subsequent pandemic threats. We declare no competing interests. Severity of omicron variant of concern and effectiveness of vaccine boosters against symptomatic disease in Scotland (EAVE II): a national cohort study with nested test negative design Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa Outcomes of laboratoryconfirmed SARS-CoV-2 infection in the omicron-driven fourth wave compared with previous waves in the Western Cape Province, South Africa. medRxiv 2022 Early assessment of the clinical severity of the SARS-CoV-2 omicron variant in South Africa: a data linkage study Imperial College COVID-19 Response Team