Operation Nasal Vaccine-Lightning speed to counter COVID-19

Summary: Although SARS-CoV-2 mainly infects the upper respiratory tract, little is known about the antibodies generated in the oral cavity in response to COVID-19 vaccination. This study found that most participants had detectable antibodies in their saliva after the first dose of mRNA vaccine. The second dose boosted the IgG response but had little effect on the IgA response. Participants with lower levels of vaccine-induced IgA were more likely to experience breakthrough infections.

Summary: SARS-CoV-2 mRNA vaccination induces strong immune responses in the circulation, but its effectiveness in the respiratory tract, especially against variants of concern like Omicron, is still uncertain. This study found lower neutralizing antibody responses in the respiratory tract of vaccinated individuals compared to COVID-19 convalescents, despite robust antibody responses in the blood. Vaccination also induced circulating B and T cell immunity, but these responses were absent in the respiratory tract. Mouse immunization experiments showed that systemic mRNA vaccination alone resulted in weak respiratory mucosal neutralizing antibody responses, but combining it with mucosal adenovirus-S immunization produced strong neutralizing antibody responses against both the ancestral virus and the Omicron variant. Overall, this study suggests that current COVID-19 vaccines are highly effective against severe disease, but provide limited protection against breakthrough infections, particularly by the Omicron sublineage.

Summary: Research has shown that SARS-CoV-2-specific immune memory persists in organs for up to 6 months post-infection, with lungs and lymph nodes being the most prevalent sites, indicating coordinated local tissue immunity for protection against future infections.