[COVID-19 deaths: a comparison between epidemiological surveillance data and the National Institute of Statistics...

To compare the number of COVID-19 deaths reported daily by the autonomous communities to System for Surveillance in Spain (SiVIES) with the consolidated data from the National Statistics Institute (INE) between March 2020 and December 2022.

The number of confirmed COVID-19 deaths recorded in SiVIES and the INE (ICD-10 code U07.1 as the underlying cause of death) was analysed by mortality period, sex, age, and autonomous community. In a second step, deaths with suspected COVID-19 (INE: ICD code U07.2; SiVIES: possible or probable cases, notified up to May 2020) were included.

In SiVIES, 118,557 confirmed COVID-19 deaths were reported, 9.8% fewer than in the INE (131,408). The difference was smaller in the central periods (between -5.7% and -7.9%) and larger in women (-11%), those aged ≥80 (-12%), and in Catalonia and Galicia (-18%). When including suspected COVID-19, the difference increased from -13% to -36% in the first period (until June 2020), when both sources collected suspected cases. In later periods, the differences were smaller, despite SiVIES reporting only confirmed cases.

The difference in confirmed COVID-19 deaths reported in SiVIES vs. INE was <10% overall, with differences by age, sex, and autonomous community. The smaller differences after the first period may be attributed to improvements in the surveillance system, and the widespread availability of diagnostic tests may explain the low impact of including suspected cases.