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

Brumme ZL, Mwimanzi F, Lapointe HR, Cheung P, Sang Y, Duncan MC, Yaseen F, Agafitei O, Ennis S, Ng K, Basra S, Lim LY, Kalikawe R, Speckmaier S, Moran-Garcia N, Young L, Ali H, Ganase B, Umviligihozo G, Omondi FH, Atkinson K, Sudderuddin H, Toy J, Sereda P, Burns L, Costiniuk CT, Cooper C, Anis AH, Leung V, Holmes D, DeMarco ML, Simons J, Hedgcock M, Romney MG, Barrios R, Guillemi S, Brumme CJ, Pantophlet R, Montaner JSG, Niikura M, Harris M, Hull M, Brockman MA. Humoral immune responses to COVID-19 vaccination in people living with HIV on suppressive antiretroviral therapy. medRxiv. 2021 Oct 4. doi:

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

Researchers Drs. Zabrina Brumme and Mark Brockman from the BC Centre for Excellence in HIV/AIDS and Simon Fraser University have determined that antibody responses following one COVID-19 vaccine dose are modestly lower in people living with HIV compared to individuals without HIV. However, they report that the discrepancy disappears after the second dose. These findings, available in preprint and therefore not yet peer-reviewed, emerge from a CITF-funded pan-Canadian study headed by Dr. Aslam Anis of the Canadian HIV Trials Network.

Key findings:

  • Antibody responses to COVID-19 vaccines following one dose were modestly lower in people living with HIV compared to individuals without HIV, but these differences disappeared after the second dose.
  • Among people living with HIV, there was no significant relationship between the most recent or the lowest ever recorded CD4+ T-cell count and the response to two vaccine doses, meaning those with low CD4+ T-cell counts in the past can still mount an adequate immune response.

One hundred people living with HIV in British Columbia were recruited for this study; all participants were on suppressive antiretroviral therapy, with almost all having immune cell counts within a healthy range. A control group included 152 people without HIV. Participants provided blood samples prior to COVID-19 vaccination (if feasible), as well as one month after the first vaccine dose, and one month after the second dose. The study team measured antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, as well as the ability of these antibodies to disrupt the interaction between RBD and its cellular receptor ACE2, after one and two doses of a COVID-19 vaccine.

Results indicated that antibody responses to COVID-19 vaccines following one dose were lower in people living with HIV compared to the controls, though the magnitude of this difference was relatively modest. Of note, after two doses of vaccine, the antibody response of people living with HIV were on par with individuals without HIV. Factors associated with weaker antibody responses after two doses were: older age, having a higher number of chronic health conditions, and having received two doses of AstraZeneca’s Vaxzevria vaccine (as opposed to a mixed or dual mRNA vaccine regimen).

Importantly, among people living with HIV, the researchers observed no significant relationship between their most recent or lowest ever recorded (i.e., nadir) CD4+ T-cell count and their response to COVID-19 vaccination following two vaccine doses. The nadir CD4+ T-cell counts in the study participants ranged as low as <10 CD4+ T-cells/mm3. This indicates that, for people living with HIV who are currently receiving treatment, having had low CD4+ T-cell counts in the past will not necessarily compromise immune responses to COVID-19 vaccines.

The authors offer that, for most people living with HIV whose infection is well-controlled with therapy and whose CD4+ T-cell counts are in the healthy range, third COVID-19 vaccine doses may not be immediately required. That said, other factors such as older age, co-morbidities, type of initial vaccine regimen, and durability of vaccine responses will influence when individuals from this population may benefit from additional doses. Further studies of people living with HIV who are not receiving antiretroviral treatment or who have low CD4+ T-cell counts are also needed.