Introduction:

The study of anti-SARS-CoV-2 IgG antibodies allows asymptomatic individuals with COVID-19 to be identified, and post-infection and post-vaccination immunity status to be evaluated.

Objective:

To know the behavior of anti-SARS-CoV-2 IgG antibodies before and after vaccination in workers of a cancer center.

Methods:

Prior to the application of the vaccine, the presence of anti-SARS-CoV-2 IgG antibodies (n = 171) was analyzed by evaluating anti-N IgG antibodies; post-vaccination, after receiving the second dose, anti-S IgG antibodies were evaluated (n = 60).

Results:

Prior to vaccination, IgG antibodies were present in 18.71% of participants; they were detected in 65.22% of those with prior history of COVID-19 diagnosis and in 11.49% of those without it. The positions with the highest prevalence were nurses (28.26%), paramedics (27.59%) and administrative workers (27.78%), p < 0.01. Anosmia, ageusia and chest tightness were associated with the presence of IgG (p < 0.05). Post-vaccination, all participants developed IgG antibodies; people with a previous COVID-19 diagnosis had higher titers: 10,277 vs. 6,819 AU/mL, p < 0.001.

Conclusions:

The study of anti-SARS-CoV-2 IgG allowed asymptomatic health workers to be identified. A high percentage of participants with prior COVID-19 diagnosis had antibodies. All participants developed IgG after vaccination, with higher titers being identified in those with previous infection.