Background: The presence of SARS-CoV-2-IgG is directly correlated with the degree of vaccine efficacy. Recent studies have shown the presence of this antibody in the blood and milk of breastfeeding mothers vaccinated with mRNA (Pfizer). However, limited information is available in lactating women that received other vaccine platforms used in developing countries, such as the inactivated SARS-CoV-2 vaccine and the non-replicating adenovirus vaccines. Objective: To compare the amount anti-SARS-CoV-2 IgG protein in the blood and milk of lactating women vaccinated against SARS-COV-2 based on vaccine platforms used. Methods: A cross-sectional study was carried out with 48 Brazilian lactating women, over 18 years old, contacted by the main social networks. The milk and blood collection will be carried out by professionals previously trained in the human milk bank and clinical laboratories. For the detection of SARS-CoV-2-IgG in samples of blood and breast milk, the technicians used the method of direct enzyme immunoassay (ELISA). Results: From the total number of lactating women evaluated, 48% received the vaccine with mRNA, 29.2% non-replicating adenovirus and 23% inactivated SARS-COV-2. The average of IgG in blood (5.39) was higher than in milk (1.19), but without significant difference when comparing the results obtained using different vaccine platforms. Most lactating women received the second Pfizer booster dose. There was a reduction in the amount of IgG between the first dose and the second booster dose. However, after applying the second booster dose (40), regardless of the vaccine manufacturer, there was an increase in the average levels of IgG in blood (5.50) and in milk (1.25). Conclusions: The present study showed that, regardless of the technology used in developing countries, after the second booster dose there was an increase in the levels of IgG in the blood and milk of nursing mothers, reinforcing the importance of completing vaccination schedule.