Irish research finds more accurate indicator of Covid-19 vaccine efficacy

Reference: April 2025 | Issue 4 | Vol 11 | Page 42

Research led by the Centre for Experimental Pathogen Host Research (CEPHR) at University College Dublin has found that memory B cells are a more accurate indication of Covid-19 vaccine protection than antibody titres or T-cell responses.

A clear immune correlate of protection from SARS-CoV-2 infection has been lacking. Researchers led by the CEPHR explored antibody, B-cell, and T-cell responses following the third dose of vaccine and their relationship to incident SARS-CoV-2 infection.

A total of 132 adults in a prospective cohort provided blood samples at day 0, day 14, and 10 months after the third dose of SARS-CoV-2 vaccine. Participants self-reported incident SARS-CoV-2 infection. Plasma anti-SARS-CoV-2 receptor-binding domain (RBD) and spike-subunit-1 and spike-subunit-2 antibodies were measured.

A sub-study assessed SARS-CoV-2-specific plasma and memory B-cell and memory T-cell responses in peripheral blood mononuclear cells by enzyme-linked immunospot. Comparative analysis was carried out on participants who developed incident infection and uninfected participants.

Approximately 36 per cent (n=47) of participants reported incident SARS-CoV-2 infection at a median 16.5 (16.25-21) weeks after the third-dose vaccination. RBD titres and B-cell responses, but not T-cell responses, increased after the third-dose vaccine.

At day 14 there was no significant difference in antibody titres or T-cell responses between participants with and without incident SARS-CoV-2 infection. However, RBD memory B-cell frequencies were significantly higher in those who did not develop infection (10.0% versus 4.9%; P=0.01). At 10 months, RBD titres and memory B-cell frequencies remained significantly higher than day 0 levels (P<0.01).

The findings suggest that higher memory B-cell frequencies, rather than antibody titres or T-cell responses, predict protection from subsequent infection, identifying memory B cells as a correlate of protection.

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