Although it is difficult to directly compare viruses in terms of immunogenic responses, on the one hand, SARS and MERS coronaviruses readily elicit neutralizing antibodies following infection or immunization62–65. Indeed, many potential MERS-CoV vaccine candidates are able to elicit high titres of serum IgG upon immunization but fail to produce sufficient mucosal immunity65. In contrast, the high mutation rate66 and the evolving glycan shield of HIV-120,39, which firmly exemplifies it as “evasion strong” virus, hinders the development of broadly neutralizing antibodies67.Viruses classified as “evasion strong”26,56 may then differ due to varied efficacies of protein surface shielding by glycans.