Table 1. Overview of included ICPC-1 codes per group.

ICPC-1 code	Influenza group	SARS-CoV-2 group
R74 Acute upper respiratory infection	Yes	Yes
R75 Acute/chronic sinusitis	Yes	Yes
R77 Acute laryngitis/tracheitis	Yes	Yes
R78 Acute bronchitis/bronchiolitis	Yes	Yes
R80 Influenza	Yes	Yes
R81 Pneumonia		Yes, excluding R81.01 Legionella pneumonia
R83 Other respiratory infection		Yes, excluding R83.01 Diphtheria and R83.02 Sarcoidosis

ICPC-1 = International Classification of Primary Care first edition. SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2.