This story was updated in February 2022 to show that this original story, published in October 2020, is out of date, and adds new information.
From the editors: This article, describing a letter written in The Lancet, was published in October 2020, 2 months before the emergency use authorization of the first COVID-19 vaccine in the United States. It also discusses a type of vaccine that is not currently in use in the United States for SARS-CoV-2, the virus that causes COVID-19.
All available data suggest that the currently authorized COVID-19 vaccines are safe and effective.
For more information, see:
From the CDC: What to Know About HIV and COVID-19
From the HIV Medicine Association: COVID-19 Vaccines and People With HIV
*Three vaccines were authorized by the FDA for emergency use in the United States for COVID-19 after this article was published. Two of these, from Pfizer-BioNTech and Moderna, have been fully approved by the FDA since January 31, 2022. This article was edited on February 7, 2022, to add these clarifications, to note the approvals, and to change the story to past tense.
As the race to approval of a safe and effective vaccine for coronavirus disease 2019 (COVID-19) continues*, a group of researchers said some of these vaccines could make patients more susceptible to contracting HIV.
Writing a letter in The Lancet, the researchers urged caution when it comes to the use of adenovirus type-5 (Ad5) vectored vaccines for COVID-19, recalling their research from a decade ago on an Ad5 vectored vaccine in 2 HIV vaccine trials.
“On the basis of these findings, we are concerned that use of an Ad5 vector for immunisation against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could similarly increase the risk of HIV-1 acquisition among men who receive the vaccine,” wrote the researchers. “Both the HIV and COVID-19 pandemics disproportionately affect vulnerable populations globally. Roll-out of an effective SARS-CoV-2 vaccine globally could be given to populations at risk of HIV infection, which could potentially increase their risk of HIV-1 acquisition.”
The group’s ”cautionary tale” stemmed from the Step and Phambili phase 2b trials that studied the efficacy of an Ad5 vectored HIV-1 vaccine in preventing HIV infection. Across both international studies, they found that the vaccine actually increased the risk of HIV among the vaccinated men.
The findings from the Phambili study, in particular, have important implications for the use of the vaccines in COVID-19, said the researchers, as findings from this study showed that heterosexual men receiving the Ad5 vectored vaccine faced a consistently increased risk of HIV infection. Notably, this increased risk appeared to be limited to men, with women not having an observed increase of infection in the study.
In the Step trial, the risk of acquiring HIV was particularly high among men who were uncircumcised and Ad5 seropositive men who reported having unprotected anal sex with a partner who was HIV seropositive or who had unknown serostatus as baseline.
Of note, the vaccine in both studies did not have the HIV envelope. Meanwhile, in another study that used a DNA prime and an Ad5 vector, both of which had the HIV envelope, there was no observed increase in HIV infection.
The reason for the observed increase in HIV risk remains uncertain, although several follow-up studies have suggested a potential explanation, according to the researchers.
“The vaccine was highly immunogenic in the induction of HIV-specific CD4 and CD8 T cells; however, there was no difference in the frequency of T-cell responses after vaccination in men who did and did not later become infected with HIV in the Step Study,” they wrote. “These findings suggest that immune responses induced by the HIV-specific vaccine were not the mechanism of increased acquisition. Participants with high frequencies of preimmunisation Ad5-specific T cells were associated with a decreased magnitude of HIV-specific CD4 responses and recipients of the vaccine had a decreased breadth of HIV-specific CD8 responses, suggesting that pre-existing Ad5 immunity might dampen desired vaccine-induced responses.”
Other exploratory studies have indicated that the vaccine enhances HIV replication in CD4 T cells or that Ad5-specific CD4 T cells could be more susceptible to HIV infection.
Buchbinder SP, McElrath MJ, Dieffenback C, Corey L. Use of adenovirus type-5 vectored vaccines: a cautionary tale. Lancet. Published online October 19, 2020.doi:10.1016/S0140-6736(20)32156-5