This cohort study aimed to compare serum and salivary IgG and IgA levels among individuals vaccinated with messenger RNA (mRNA) vaccines, both with and without a previous SARS-CoV-2 infection. The study included 427 participants, divided into three groups: those with a previous SARS-CoV-2 infection who received a single dose of the BNT162b2 (Pfizer-BioNTech) vaccine, and those without a previous infection who received either two doses of the mRNA-1273 (Moderna) vaccine or two doses of the BNT162b2 vaccine. The median age was 68 years, with 53.4% being men. Key findings include: - SARS-CoV-2 spike-specific IgG levels in saliva increased in both previously infected and naive individuals after vaccination. - SARS-CoV-2-specific saliva IgA levels were significantly higher in participants with a previous infection compared to those with no prior infection, especially after the second dose of the mRNA-1273 vaccine. - Bona fide multimeric secretory IgA levels were significantly higher in individuals with a previous infection compared to naive individuals after two antigenic stimulations. - Specific salivary IgA levels increased modestly in SARS-CoV-2-naive individuals after vaccination, particularly with the mRNA-1273 vaccine. The study suggests that mRNA vaccination can induce mucosal immunity in individuals without prior SARS-CoV-2 infection, but at lower levels compared to those with a previous infection. Further research is needed to determine the association between specific saliva IgA levels and the prevention of infection or transmission.This cohort study aimed to compare serum and salivary IgG and IgA levels among individuals vaccinated with messenger RNA (mRNA) vaccines, both with and without a previous SARS-CoV-2 infection. The study included 427 participants, divided into three groups: those with a previous SARS-CoV-2 infection who received a single dose of the BNT162b2 (Pfizer-BioNTech) vaccine, and those without a previous infection who received either two doses of the mRNA-1273 (Moderna) vaccine or two doses of the BNT162b2 vaccine. The median age was 68 years, with 53.4% being men. Key findings include: - SARS-CoV-2 spike-specific IgG levels in saliva increased in both previously infected and naive individuals after vaccination. - SARS-CoV-2-specific saliva IgA levels were significantly higher in participants with a previous infection compared to those with no prior infection, especially after the second dose of the mRNA-1273 vaccine. - Bona fide multimeric secretory IgA levels were significantly higher in individuals with a previous infection compared to naive individuals after two antigenic stimulations. - Specific salivary IgA levels increased modestly in SARS-CoV-2-naive individuals after vaccination, particularly with the mRNA-1273 vaccine. The study suggests that mRNA vaccination can induce mucosal immunity in individuals without prior SARS-CoV-2 infection, but at lower levels compared to those with a previous infection. Further research is needed to determine the association between specific saliva IgA levels and the prevention of infection or transmission.