Few studies have shown that immunocompromised individuals may mount attenuated antibody responses, compared to their otherwise healthy counterparts. A new pre-print, therefore not yet peer-reviewed, by CITF-funded researcher Dr. Andrés Finzi and Dr. Cécile Tremblay, both from the University of Montréal, found that the immunogenicity of a single dose of the Moderna vaccine in people living with HIV depended on their CD4+ T cell count.

In people living with HIV (PLWH), an essential component of the immune system that helps orchestrate both cellular and humoral (antibody-based) immunity (CD4+ T cells) are targeted by the HIV virus. Previous studies have shown that PLWH may mount lower antibody responses to vaccines, contingent on the level of their CD4+ T cell counts. Fortunately, the majority of PLWH who are being treated with well-tolerated antiretroviral drugs tend to achieve immune recovery with normalized CD4+ T cell counts. In this study, researchers examined the immunogenicity of a single dose of Moderna’s vaccine in PLWHIV-1 (people living with HIV-1).

Key points:

  • There were no significant differences between the level of antibodies induced in PLWH compared to healthy controls following one dose of the Moderna vaccine.
  • However, PLWH with lower CD4+ T cell counts (under 250 cells/mm3) mounted significantly lower antibody responses after one dose of the vaccine compared to those with higher CD4+ T cell counts.

These findings highlight the need to consider additional strategies such as booster shots and immune-monitoring for specific populations to ensure adequate protection against COVID-19.


Nault L, Marchitto L, Goyette G, Tremblay-Sher D, Fortin C, Martel-Laferrière V, Trottier B, Richard J, Durand M, Kaufmann D, Finzi A, Tremblay C. Covid-19 vaccine immunogenicity in people living with HIV-1. bioRxiv 2021.08.13.456258. doi : https://doi.org/10.1101/2021.08.13.456258