This is a summary, written by members of the CITF Secretariat, of:

Datwani S, Kalikawe R, Waterworth R, Mwimanzi FM, Liang R, Sang Y, Lapointe HR, Cheung PK, Omondi FH, Duncan MC, Barad E, Speckmaier S, Moran-Garcia N, Demarco ML, Hedgcock M, Costiniuk CT, Hull M, Harris M, Romney MG, Montaner JSG, Brumme ZL, Brockman MA. Dynamics of T cell responses to COVID-19 vaccines and breakthrough infection in people living with HIV receiving antiretroviral therapy. medRxiv. 2024 March 11. doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published as a pre-print and not yet peer-reviewed, found that people living with HIV (PLWH) receiving antiretroviral therapy mount strong T cell responses to COVID-19 vaccines that are enhanced by booster doses or breakthrough infection. This study was led by Dr. Mark Brockman in collaboration with Dr. Zabrina L. Brumme (both from Simon Fraser University) and Dr. Marc Romney (Providence Health Care and University of British Columbia).

The study recruited 50 PLWH and 87 controls and measured SARS-CoV-2 spike-specific CD4+ and CD8+ T cell responses generated by up to three doses of an mRNA vaccine. Additional T cell responses following a breakthrough infection or a fourth dose were also quantified for a subset of PLWH (n=21). All participants remained SARS-CoV-2 naïve until at least one month after their third vaccine dose.

Key findings:

  • A third vaccine dose boosted spike-specific CD4+ and CD8+ T cell frequencies significantly above those measured after the second dose (all p<0.0001).
  • CD8+ T cell responses were modestly lower in PLWH after the third dose (p=0.02), even after adjustment for sociodemographic, health, and vaccine-related variables (p=0.045).
  • Among 21 PLWH who experienced breakthrough infection, median T cell frequencies increased even higher than those observed after three vaccine doses (p<0.03).
  • CD8+ T cell responses in PLWH who had a breakthrough infection remained higher even after a fourth vaccine dose (p=0.03), compared to responses in SARS-CoV-2 naïve PLWH who received a fourth dose.
  • In multivariable analysis, only younger age was associated with increased breakthrough infection risk.

The results from this study add to the growing body of evidence that PLWH mount strong cellular immune responses to COVID-19 vaccines and further underscore the benefit of vaccinating this population.