Collaborative study examines COVID-19 vaccine immune responses in people living with HIV

November 23, 2021

BC Centre for Excellence in HIV/AIDS (BC-CfE) researchers, collaborating with counterparts at Simon Fraser University, the University of BC, Providence Health Care and the CIHR Canadian HIV Trials Network (CTN) recently published a study looking at COVID-19 vaccine immune responses in people living with HIV (PLWH).

Due to the explosive growth of COVID-19 variants, and the ongoing discussion about third vaccine shots and their necessity, the researchers released their findings earlier than originally planned. The need to expedite the research was also spurred by the timeline for decisions regarding additional COVID-19 vaccine doses for some key populations in BC including PLWH. By providing local data, the collaborative hoped to generate data that would assist decision-makers.

Titled, “Humoral immune responses to COVID-19 vaccination in people living with HIV receiving suppressive antiretroviral therapy”, the publication is currently in its pre-print stage pending peer review.

The study recruited 100 people living with HIV, all of whom were on suppressive antiretroviral therapy and where 98% of this group had a CD4+ T cell count greater than 200 cells/mm3, (a CD4+ T cell count below 200 cells/mm3 is an indicator of immunodeficiency). The study also recruited 152 individuals without HIV, ranging from 22 to 88 years of age, as a control group. Participants provided blood samples prior to COVID-19 vaccination, if feasible, one month after the first vaccine dose, and one month after the second dose. The researchers measured the levels of circulating antibodies against the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, the ability of these antibodies to disrupt the interaction between RBD and its cellular receptor ACE2, and the ability of these antibodies to block infection of cells by SARS-CoV-2, the virus that causes COVID-19, after one and two doses of COVID-19 vaccine.

Study results indicated that after a single COVID-19 vaccine dose, and after accounting for sociodemographic, health and vaccine-related variables, the antibody responses to COVID-19 vaccines in people living with HIV were lower than those of controls, although the magnitude of this difference was relatively modest. However, after two COVID-19 vaccine doses, this effect disappeared. That is, after two doses of COVID-19 vaccine, the antibody responses of people living with HIV were comparable to those of controls.

The study found that, rather than HIV, older age, a higher number of chronic health conditions, and having received two doses of the AstraZeneca vaccine (as opposed to a mixed or dual mRNA vaccine regimen), were the most significant correlates of weaker antibody responses after two doses.

Importantly, among PLWH the researchers observed no significant relationship between either their most recent nor their lowest ever recorded CD4+ T-cell counts and responses to COVID-19 vaccination following two vaccine doses.

This indicates that, for PLWH who are currently receiving suppressive antiretroviral therapy, having had low CD4+ T-cell counts in the past will not necessarily compromise their immune responses to COVID-19 vaccines presently.

In concluding their study, the researchers interpreted the results as suggesting that PLWH whose viral loads are well-controlled on antiretroviral therapy and whose CD4+ T-cell counts currently are in a healthy range should generally not require a third COVID-19 vaccine dose as part of their initial immunization series. The study notes how other factors such as older age, co-morbidities, type of initial vaccine regimen and durability of vaccine responses will influence when PLWH may benefit from additional doses.

The researchers also emphasize that the study’s findings may not be generalizable to PLWH who are not receiving treatment and/or whose CD4+ T-cell counts are currently less than 200 cells/mm3, and that further studies of these groups are needed.

Dr. Zabrina Brumme, the BC-CfE Laboratory Director and the lead author of this study, said “In the coming weeks and months, we will be continuing this study to monitor the durability of these responses, and we look forward to sharing additional results as they come in”

This study was made possible through funding from Genome BC, the Michael Smith Foundation for Health Research, the BCCDC foundation for Public Health, the Canada Foundation for Innovation and the Public Health Agency of Canada through the COVID-19 Immunity Task Force. It is also part of a pan-Canadian study of immune responses in PLWH headed by Dr. Aslam Anis of the CIHR Canadian HIV Trials Network. The views expressed in this publication are those of the researchers and not necessarily those of the funding agencies.

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Collaborative study examines COVID-19 vaccine immune responses in people living with HIV

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