THE end of HIV is "on the horizon" - as the first vaccine to tackle the virus could be available by as soon as 2021, scientists believe.
Researchers say they are "optimistic" about the future, as trials of three different vaccines are close to entering their final stages.
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Results of the vaccine experiments, known as HVTN 702, Imbokodo and Mosaico, will be available as early as next year.
When a person is diagnosed with HIV, doctors start them on antiretroviral treatment straight away.
The combination of three drugs - typically taken in one tablet - work to stop the virus replicating in the body.
By doing so, it reduces a person's viral load - the amount of HIV in the blood.
One step closer
Once a person's viral load drops below a certain threshold, it is described as being undetectable - which means they cannot pass the virus on to a sexual partner, even if they have unprotected sex.
While the treatment is highly effective, it does not amount to a cure.
Instead the virus does remain active - though at a very low level - in the body.
If antiretroviral therapy is stopped, these HIV reservoirs that lie dormant, can reawaken.
Despite this, the trials raise hopes that scientists are one step closer to finding a vaccine.
Tremendous breakthrough
Chair of two of the trials, Dr Susan Buchbinder, director of the Bridge HIV research program at the San Francisco Department of Public Health, said this is "perhaps one of the most optimistic moments we have been in".
And she said even a partially effective vaccine would be "a tremendous breakthrough" and "would really have the power to change the trajectory of the epidemic".
Dr Buchbinder told NBC: "We have three vaccines currently being tested in efficacy trials, and it takes quite a bit to actually be promising enough in the earlier stages of trials to move you forward into an efficacy study."
The oldest ongoing HIV vaccine trial - known as HVTN 702 - was launched in South Africa in 2016.
We have three vaccines currently being tested in efficacy trials, and it takes quite a bit to actually be promising enough in the earlier stages of trials to move you forward into an efficacy study
Dr Susan Buchbinder
It's based on a prior candidate, RV144, which lowered the rate of HIV infections by around 30 per cent in an older study.
RV144 remains the only HIV vaccine that has ever demonstrated any efficacy against the virus - however, scientists wanted to make it stronger.
The second trial, of Imbokodo, began in five southern African nations in 2017.
Imbokodo uses "mosaic" immunogens, which are "vaccine components designed to induce immune responses against a wide variety of global HIV strains", according to the National Institutes of Health.
The third vaccine, dubbed Mosaico, is also based on this unique mosaic immunogen approach and trial of it started in November.
What are the symptoms of HIV?
Most infected people experience a short illness, similar to flu, two to six weeks after coming into contact with HIV.
These symptoms, which 80 per cent of infected people experience, are a sign that their body is trying to fight HIV. They include:
- Fever
- Sore throat
- Body rash
- Tiredness
- Joint and/or muscle pain
- Swollen glands
After this illness, which normally lasts one to two weeks, HIV sufferers will have no symptoms for up to 10 years - during which time they will look and feel well.
However, the virus will continue to cause progressive damage to a person's immune system.
Only once the immune system is already severely damaged will the person show new symptoms. These include:
- Weight loss
- Chronic diarrhoea
- Night sweats
- Skin problems
- Recurrent infections
- Serious, life-threatening illnesses
Imbokodo and Mosaico are very similar in formula and mosaic vaccines are expected to give broader coverage to different strains of HIV.
The two vaccines consist of six injections, with slightly different types administered during the final two clinic visits.
It comes after it was revealed that Britain is "on course" to be a HIV-free nation by 2030 - as rates fall to lowest level in almost two decades.
New diagnoses fell by just over a quarter from 6,721 in 2015 to 4,484 last year, Public Health England said.
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Health bosses say the continued decline in the virus is down to the success of preventative measures.
But they warn that challenges remain, with figures showing that almost half of people newly diagnosed last year were at a late stage of infection - increasing their risk of death.
The biggest falls in new diagnoses have been among gay and bisexual men, particularly those who are white, born in the UK, aged between 15 and 24 and living in London, the figures show.
Dr. Ranj Singh has HIV test LIVE on This Morning