The following is a summary of “Longitudinal Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine Antibody Responses and Identification of Vaccine Breakthrough Infections Among Healthcare Workers Using Nucleocapsid Immunoglobulin G” published in the December 2022 issue of Infectious Disease by Anderson et al.

The longevity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies must be understood, as well as the effects of booster doses on antibody levels and resistance to infection, through long-term investigations of vaccination recipients. Understanding vaccine effectiveness and the ability of SARS-CoV-2 to escape the vaccine will depend on the ability to detect vaccine breakthrough infections among people that have received all recommended vaccinations.

Longitudinal research including 1,000 Chicago healthcare workers who were either infection-naive or had already been infected before receiving the vaccine evaluated the levels of SARS-CoV-2 spike (S) receptor-binding domain and nucleocapsid (N) immunoglobulin (Ig) G. Following changes in S and N IgG for 14 months, vaccination breakthrough infections were found by rising N IgG levels.

SARS-CoV-2 S IgG antibody levels declined consistently for 11 months following immunization in both previously infected and previously uninfected people. A booster administered 8–11 months after immunization boosted S IgG levels by >2-fold over those seen after 2 doses, resulting in unidentifiable S IgG levels between people who had previously been infected and those who hadn’t. Increases in N IgG were used to detect infections caused by vaccine breakthroughs and revealed >15% infection rates during the Omicron wave beginning in December 2021.

Based on N IgG increases; the findings showed SARS-CoV-2 antibody alterations following vaccination and breakthrough infections. They also highlighted significant numbers of vaccine breakthrough infections during the Omicron wave.