What’s New: A study on a Canadian interprovincial cohort of healthcare workers (HCWs) has provided insights into the factors influencing the immune response to SARS-CoV-2 vaccination, measured by anti-RBD IgG levels, over time.

Importance: Understanding the dynamics of the immune response following vaccination and infection is crucial for optimizing vaccination strategies and managing patient care, especially for those with immunocompromising conditions.

Contributions to Literature: This research contributes to the literature by using a longitudinal approach to assess the immune response in HCWs, considering multiple factors such as vaccine type, infection history, immunocompromising conditions, and therapies.

Results Summary:
– A total of 2,752 out of 4,567 vaccinated HCWs provided blood samples.
– Analysis of 8,903 samples showed increased anti-RBD IgG levels with each vaccine dose and after the first infection.
– IgG levels decreased over time, with the most significant drop after the third vaccine dose.
– The mRNA1273 (Moderna) vaccine led to higher anti-RBD IgG levels.
– Lower IgG levels were associated with certain conditions (multiple sclerosis, rheumatoid arthritis) and the use of specific immunosuppressants.
– Higher IgG levels were reported by participants experiencing side-effects post-vaccination.
– No significant relationship was found between anti-RBD IgG levels and obesity.
– Women vaccinated in early or mid-pregnancy had lower IgG titers.
– Self-reported data were considered reliable based on sensitivity analysis.

The study’s prospective cohort design and serial serology assessments provide accurate effect estimates and a comprehensive understanding of the factors affecting vaccine response.