Improved Approach to Coronavirus Vaccines Works in Animals

Despite the remarkable success of mRNA vaccines for COVID-19, systemic immunity against SARS-CoV-2 tends to wane. Also, because intramuscular (IM) vaccines don't produce robust local immune responses against virus in the nose, they are suboptimal at preventing viral transmission. Traditional nasal vaccines have proved ineffective, and nasal vaccines with adjuvants have been associated with adverse reactions.

A team from Yale assessed, in mice and hamsters, whether an mRNA vaccine administered intranasally 2 weeks after an IM vaccine would generate both systemic immunity and the nasal mucosal immunity that IM vaccines and boosters do not achieve. Indeed, the nasal vaccine regimen induced nasal mucosa–resident memory CD8 and CD4 cells and B cells, systemic and local IgA and IgG antibodies, and better T-cell immune responses than a regimen that used an IM booster. Presumably as a result, when challenged with virus, nasal vaccine recipients had less virus in the nose and a lower viral transmission rate than IM booster recipients. As an added benefit, the combination of an IM mRNA vaccine and a nasal vaccine booster offered protection against another coronavirus, SARS-CoV-1 (the cause of severe acute respiratory syndrome [SARS]).