Publication date: Apr 28, 2026
Despite hybrid and vaccine-induced immunity, SARS-CoV-2 continues to cause disease. The characterization of humoral and cellular immune responses is essential for guiding prevention strategies and booster dose policies; Methods: A prospective cohort study was conducted with 131 hospitalized patients with confirmed COVID-19 in the AburrcE1 Metropolitan Valley, Colombia. Clinical and immunological data were evaluated on days 1-3, days 5-7, days 8-12, and 4-5 months after diagnosis. Humoral immunity was assessed by enzyme-linked immunosorbent assay (ELISA), chemiluminescent microparticle immunoassay (CMIA), and neutralization testing, and cellular immunity by CD4/CD8 T-cell responses. vaccinated patients had higher baseline levels of IgG and neutralizing antibody positivity than unvaccinated patients (ELISA 89. 1% vs. 60. 0%; CMIA 86. 4% vs. 50. 0%; neutralizing antibodies 88. 2% vs. 65. 0%), but cases of severe disease occurred in both groups. Adults aged ≥65 years had higher antibody positivity, but severe disease persisted. Mortality at 28 days was 7. 6%, mainly among critically ill patients with comorbidities. Antibodies persisted at 4-5 months but were lower in those with severe acute disease. Those who received the booster dose showed stronger CD4/CD8 activation (notably against the Omicron variant) than unvaccinated/partially vaccinated patients. Vaccination improved humoral and cellular responses, but severe breakthrough infections still occurred, particularly in high-risk patients.
| Concepts | Keywords |
|---|---|
| Cd4 | breakthrough infections |
| Colombia | cellular immunity |
| Elisa | comorbidities |
| Months | COVID-19 |
| Vaccine | humoral immunity |
| mRNA vaccines | |
| neutralizing antibodies | |
| SARS-CoV-2 | |
| T cells |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | COVID-19 |
| disease | MESH | critically ill |
| disease | MESH | acute disease |
| disease | MESH | breakthrough infections |