Primary care for patients with respiratory tract infection before and early on in the COVID-19 pandemic: an observational study in 16 European countries by van der Velden, AW, Bax, EA, Bongard, E, Munck Aabenhus, R, Anastasaki, M, Anthierens, S, Balan, A, Böhmer, F, Bruno, P, Chlabicz, S, Coenen, S, Colliers, A, Emmerich, S, Garcia-Sangenis, A, Ghazaryan, H, van der Linde, SR, Malania, L, Pauer, J, Tomacinschii, A, Tonkin-Crine, S, Vellinga, A, Zastavnyy, I, Verheij, T, Goossens, H, Butler, CC