Vaccines play a critical role in preventing respiratory infections by limiting virus circulation, especially in the case of COVID-19. For effective prevention, vaccines must stimulate mucosal immunity – an immune response in the respiratory tract where viruses like SARS-CoV-2 typically enter the body. However, the extent to which current mRNA-based COVID-19 vaccines generate mucosal immunity has remained largely unexamined.
A recent study has addressed this gap by evaluating mucosal neutralising antibody responses among 183 individuals following primary vaccination with either adenovirus vector or mRNA vaccines, as well as after mRNA booster doses. The study’s findings show that repeated mRNA vaccinations lead to the presence of neutralising antibodies against SARS-CoV-2 in nasal secretions. These antibodies, specifically IgG and IgA types, were found in both nasal and serum samples, with their levels closely correlating between the two.
To understand the source of these mucosal antibodies, researchers used a mouse model, administering repeated mRNA vaccines. The results showed that while neutralising antibody-producing cells were located in the spleen and bone marrow, they did not directly migrate to the respiratory mucosa. Instead, the study suggests that circulating antibodies in the blood may move to the respiratory mucosa, providing an indirect source of mucosal immunity.
These findings are significant in illustrating how mRNA vaccines, especially when boosted, can encourage mucosal immunity against SARS-CoV-2. Additionally, they highlight the possibility that vaccination could enhance mucosal immunity generated by prior infections. This research contributes essential knowledge to the field, shaping future strategies for developing vaccines that can more effectively prevent respiratory virus transmission by targeting mucosal immunity.
Reference
Declercq J et al. Repeated COVID-19 mRNA-based vaccination contributes to SARS-CoV-2 neutralizing antibody responses in the mucosa. Sci Transl Med. 2024;16(770):eadn2364.
