Is There an HIV Vaccine?

On May 18, the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (NIAID) observes HIV Vaccine Day to promote awareness and education of HIV vaccine research and thank the individuals working on development and outreach.¹

For many years, researchers have worked to develop a vaccine to better prevent HIV and HIV-based mortality. Numerous trials have started and stopped for potential vaccines, all with varying results in terms of safety and efficacy. Researchers have made significant strides over the years; patients with HIV are able to take medicines that can help prolong their lives and make it less likely they transmit HIV to their sexual partners. Still, those who are at risk and looking for preventative measures may still be wondering: is there an available vaccine that is able to prevent HIV?

Is There an HIV Vaccine?

Currently, there is no HIV vaccine available to patients. Though there have been advances in how researchers understand HIV and how a vaccine may be developed, many recent trials for vaccines have been shelved due to their poor efficacy in preventing HIV.

However, new trials have begun in the wake of the previous trials, and research is ongoing. While the medical field does not yet know when an HIV vaccine will be made available to patients and how it will work to prevent the virus, investigators working on developing a vaccine are plentiful.

What Has Made HIV Vaccine Development Difficult?

The human immunodeficiency virus is unique in the way it will disguise itself to avoid being successfully targeted by antibodies.² HIV is able to integrate into a host genome. This means that when attempted vaccines have created targeted antibodies designed to induce T cells, those cells were not able to recognize HIV as a virus separate from the genome. As a result, the ways a vaccine can be created for HIV become significantly more limited.

Recent HIV Vaccine Trials

Though there are currently trials underway for HIV vaccines, several recently discontinued studies mean there are not currently any vaccines in late-stage trials.³ The most recent was Mosaico, Janssen’s large-scale HIV vaccine trial, which was in phase 3. The trial had been ongoing since 2019 with a vaccine that had been given to 3,900 people. Though the vaccine was deemed safe, it was not shown effective enough to continue, and Janssen’s parent company Johnson & Johnson ended the trial in January.

Recently, Janssen had a different HIV vaccine in the Imbokodo trial which made it to phase 2b. This vaccine was tested on women in sub-Saharan Africa, and was similarly determined to be safe but ineffective.

Many recent vaccine trials have focused on broadly neutralizing antibodies (bnAbs), a class of rare antibodies with the potential to neutralize different HIV strains simultaneously.⁴ Though promising, using bnAbs has proven to be a difficult process; the B cell precursors that develop into B cells that produce bnAbs are rarely activated by the proteins that form a protection for HIV. In addition, using antibody administration to prevent infection is a passive form of immunization compared to the active form that generally occurs as a result of vaccination.⁵ Many researchers hold out hope that bnAbs will help with an HIV vaccine, particularly as they develop ways to optimize the potency of antibodies and make them last longer.

Another technology researchers hope can provide advances in vaccine efficacy is messenger RNA (mRNA). In March 2022, the NIAID announced that they were launching a phase 1 trial of three HIV vaccines utilizing the same mRNA technology that had been used in certain approved COVID-19 vaccines.⁶ These vaccines deliver genetic material into the body to create a fragment of the target pathogen in hopes that the immune system can recognize it as a threat so that it can respond effectively if exposed to the actual virus. Moderna and IAVI have also recently started an mRNA vaccine trial.³

Another ongoing HIV vaccine trial, this one from Vir Biotechnology, Inc., recently received a $10 million grant from the Bill and Melinda Gates Foundation.⁷ Also funded in part by NIAID, this trial will determine the efficacy of Vir’s T cell vaccine and whether the T cells created are able to recognize different HIV epitopes. Phase 1 of this trial is expected to begin later in 2023.

Another potential vaccine from Scripps Research Institute will enter clinical trials soon.⁸ This vaccine would use protein nanoparticles to display Env, the surface protein of HIV, to present as HIV particles without causing infection. Env is covered in sugar molecules called glycans, but the nanoparticles of the vaccine shorten the glycan strands.

The world of HIV vaccine development is active but in transition; as potential vaccines in later phases of trials have been discontinued, newer ones are being tested and research continues in hopes of a new breakthrough.

HIV Prevention for Patients Without a Vaccine

With no vaccine currently available to prevent infection, those at risk should do everything they can to reduce their risk of contracting or spreading HIV. HIV is transmitted when certain bodily fluids from an HIV-positive person, such as blood, semen, or vaginal fluid, come into contact with a mucous membrane or are injected into the bloodstream.⁹ As such, two of the most important preventative measures against HIV are wearing a condom when having sex and avoiding injectable drugs. Sexually active patients should also get tested for sexually transmitted infections regularly, as they can increase the risk of HIV.

Patients who are at risk of or otherwise concerned about contracting HIV should discuss pre-exposure prophylaxis, also known as PrEP, with their clinician. PrEP is a daily medicine for reducing the risk of HIV. There is also post-exposure prophylaxis, known as PEP, which is to be taken within 72 hours of a potential exposure to the virus.