Sero-surveillance for IgG to SARS-CoV-2 at antenatal care clinics in three Kenyan referral hospitals: Repeated cross-sectional surveys 2020-21 de réir Lucinde, RK, Mugo, D, Bottomley, C, Karani, A, Gardiner, E, Aziza, R, Gitonga, JN, Karanja, H, Nyagwange, J, Tuju, J, Wanjiku, P, Nzomo, E, Kamuri, E, Thuranira, K, Agunda, S, Nyutu, G, Etyang, AO, Adetifa, IMO, Kagucia, E, Uyoga, S, Otiende, M, Otieno, E, Ndwiga, L, Agoti, CN, Aman, RA, Mwangangi, M, Amoth, P, Kasera, K, Nyaguara, A, Ng'ang'a, W, Ochola, LB, Namdala, E, Gaunya, O, Okuku, R, Barasa, E, Bejon, P, Tsofa, B, Ochola-Oyier, LI, Warimwe, GM, Agweyu, A, Scott, JAG, Gallagher, KE