Work

Temporal dynamics of IgM and IgG after COVID-19 vaccination: a pilot cohort study on breakthrough infections

Year: 2026

Type: article

Abstract: Background: During the coronavirus disease 2019 (COVID-19) pandemic, we conducted a cohort study analyzing changes in immunoglobulin (Ig) M and IgG antibody levels before and after COVID-19 vaccination. Methods: The study compared two groups: participants who were infected with severe acute respiratory syndrome coronavirus 2 within 14 days of vaccination and those who were not. We evaluated dynamic changes in IgM and IgG levels immediately following vaccination and assessed their potential correlation with infection risk. Results: Participants who contracted COVID-19 within 14 days of vaccination exhibited significantly higher IgM antibody levels than uninfected individuals, likely due to combined stimulation by both the vaccine and the virus. In the infected group, IgG antibody levels were lower than those in the uninfected group during the first 1 to 5 days post-vaccination. Moreover, across all participants, IgG antibody levels were generally lower than baseline during the first 1 to 3 days post-vaccination. Conclusions: These findings suggest that, in the early stages following vaccination, the immune system may experience a temporary "immune trough," potentially even below pre-vaccination levels. As a result, individuals should exercise additional caution during this period to mitigate infection risk.

Source: Clinical and Experimental Vaccine Research

DOI: 10.7774/cevr.2026.15.e7

Authors: Jingyun Wang, Xitong Li, Yaochen Cao, Xin Chen, Christoph Reichetzeder, Berthold Hocher