Study of Immune Response in Subjects Vaccinated Against SARS-CoV-2 Infection

Twelve months after the first SARS-CoV-2 cases in Wuhan, the FDA approved the first COVID-19 vaccine (Pfizer-BioNTech). Early studies on healthcare workers showed that antibody levels, especially against the Spike protein, declined within six months, particularly in those without prior infection. However, previously infected individuals had stronger and longer-lasting responses. The vaccine induces a Th1-type T cell response, linked to milder disease, and activates follicular helper T cells and B cell responses, although antibody levels drop over time. Immune responses also differ by sex, with females showing stronger humoral responses. Key priorities include understanding humoral fluctuations, characterizing cellular immunity, and correlating both responses.

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Key information

Conditions

SAR-CoV-2 Antibody Response Cellular Immune Response

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

IRCCS Ospedale San Raffaele

Milan, Italy, 20132

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

healthcare workers group

Inclusion criteria

Male and/or female sex

Age ≥18 years

Completion of the SARS-CoV-2 vaccination cycle with the Pfizer-BioNTech vaccine

Informed consent for the storage of biological material at the San Raffaele Hospital Biological Resource Center (with protocol related to the BioVAC study approved by the Ethics Committee: 17/INT/2022)

Availability of at least two aliquots of PBMC collected at the completion of the vaccination cycle and frozen at the CRB

Exclusion criteria

none donor group

Inclusion criteria

consent for sample collection and storage in the Biobank between 2016 and 2018

Exclusion criteria

none

Treatment and study plan

Evaluation of the T cell response in terms of IFN-γ measured by ELISpot

Other

The evaluation of the T cell response will be performed by quantifying the frequencies of SARS-CoV-2-specific T cells producing IFN-γ using an enzyme-linked immunospot assay (ELISpot), with cryopreserved PBMC collected at the designated timepoints (T0, T1, T2, T3, and T4)

Primary outcomes

To assess the existence of a correlation between the antibody titer six months after the second dose and the T and B cell responses

Time frame: Six months after the second vaccine dose, which coincides with the time of enrollment

Correlation between antibody titer, in terms of antibodies directed against the Spike protein, and T cell response, in terms of IFN-γ measured by ELISpot, as well as B cell response, in terms of frequency and phenotype, assessed six months after the second dose (T3)

Sponsors and collaborators

Lead sponsor

IRCCS San Raffaele

Other

Registry information

Official study title

Monocentric Retrospective Observational Study on Immune Response in Biological Samples Belonging to Subjects Vaccinated Against SARS-CoV-2 Infection

Acronym: BioVAC-immunit

Important dates

Study start: 2022
Primary completion: 2022
Study completion: 2024
First posted: Jul 3, 2025
Registry last updated: Jul 14, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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Completed