This study reports the rapid and robust generation of high-affinity human monoclonal antibodies (mAbs) against influenza virus following booster vaccination. After vaccination, a significant increase in antibody-secreting plasma cells (ASCs) was observed, peaking at around day 7 and accounting for up to 6% of peripheral blood B cells. These ASCs were predominantly influenza-specific, with up to 80% of purified ASCs showing specificity for the influenza vaccine strains. The ASC response was characterized by a highly restricted B-cell receptor (BCR) repertoire, with some donors showing a pauciclonal response dominated by a few B-cell clones. However, these clones showed extensive intraclonal diversification through somatic mutations, resulting in high-affinity mAbs. Using variable regions from sorted single ASCs, over 50 human mAbs were generated that bound to the three influenza vaccine strains with high affinity. This strategy demonstrated the ability to generate multiple high-affinity mAbs within a month after vaccination. The study also addressed the phenomenon of original antigenic sin (OAS), where antibodies show higher affinity for previously encountered influenza strains. However, most of the generated mAbs showed the highest affinity for the current vaccine strain, suggesting that OAS is not a common occurrence in healthy adults. The study highlights the importance of B-cell responses in generating protective immunity against influenza. It shows that influenza vaccination leads to a massive burst of IgG+ ASCs that are predominantly influenza reactive and peak around day 7 post-vaccination. The rapid accumulation of ASCs suggests a highly clonal response, which may limit the early influenza response. However, the study also found that the ASCs were mainly IgG positive, indicating their origin from the memory B-cell compartment. The study also found that the influenza-specific ASCs had accumulated more somatic mutations than normal B cells, leading to the generation of high-affinity mAbs. The mAbs generated from these ASCs showed high affinity for the influenza vaccine strains, with some neutralizing viral infection in vitro. The study concludes that the early ASC response after vaccination can be used to generate therapeutic or diagnostic mAbs rapidly to emerging influenza virus strains. The findings also suggest that the early ASC response may play a crucial role in preventing the spread of virus and resolving infections. The study provides insights into the dynamics and magnitude of the human anti-influenza response, demonstrating the potential for generating fully human mAbs within weeks of vaccination.This study reports the rapid and robust generation of high-affinity human monoclonal antibodies (mAbs) against influenza virus following booster vaccination. After vaccination, a significant increase in antibody-secreting plasma cells (ASCs) was observed, peaking at around day 7 and accounting for up to 6% of peripheral blood B cells. These ASCs were predominantly influenza-specific, with up to 80% of purified ASCs showing specificity for the influenza vaccine strains. The ASC response was characterized by a highly restricted B-cell receptor (BCR) repertoire, with some donors showing a pauciclonal response dominated by a few B-cell clones. However, these clones showed extensive intraclonal diversification through somatic mutations, resulting in high-affinity mAbs. Using variable regions from sorted single ASCs, over 50 human mAbs were generated that bound to the three influenza vaccine strains with high affinity. This strategy demonstrated the ability to generate multiple high-affinity mAbs within a month after vaccination. The study also addressed the phenomenon of original antigenic sin (OAS), where antibodies show higher affinity for previously encountered influenza strains. However, most of the generated mAbs showed the highest affinity for the current vaccine strain, suggesting that OAS is not a common occurrence in healthy adults. The study highlights the importance of B-cell responses in generating protective immunity against influenza. It shows that influenza vaccination leads to a massive burst of IgG+ ASCs that are predominantly influenza reactive and peak around day 7 post-vaccination. The rapid accumulation of ASCs suggests a highly clonal response, which may limit the early influenza response. However, the study also found that the ASCs were mainly IgG positive, indicating their origin from the memory B-cell compartment. The study also found that the influenza-specific ASCs had accumulated more somatic mutations than normal B cells, leading to the generation of high-affinity mAbs. The mAbs generated from these ASCs showed high affinity for the influenza vaccine strains, with some neutralizing viral infection in vitro. The study concludes that the early ASC response after vaccination can be used to generate therapeutic or diagnostic mAbs rapidly to emerging influenza virus strains. The findings also suggest that the early ASC response may play a crucial role in preventing the spread of virus and resolving infections. The study provides insights into the dynamics and magnitude of the human anti-influenza response, demonstrating the potential for generating fully human mAbs within weeks of vaccination.