It is hoped the pills will reduce the number of people put in hospital by the virus.
The first patients in Wales have received antiviral tablets for Covid to take at home.
The study is the first clinical trial of its kind and is being led by Oxford University.
It is being delivered by Public Health Wales, Health and Care Research Wales and Cardiff University.
The Welsh government welcomed the announcement that millions of courses of antivirals have been procured for use in the UK to treat Covid-19.
Since it started on 8 December, about 3,000 people have taken part – half of those will have taken the antiviral.
It is hoped in conjunction with vaccines and the booster programme, it will reduce the number of people put in hospital by the virus.
Christmas in hospital avoided
Amy-Claire Davies, 27 from Swansea, is a palliative care patient and has seizures from epilepsy along with severe chronic pain.
She said she and her family who also have health issues shielded from February 2020 until summer 2021 when they were all double vaccinated.
“Before having vaccinations when case rates were high, Covid was a death sentence for us because of our medical conditions,” she said.
Her dad tested positive on 24 December and the members in her household followed in the following days over Christmas.
“I had the tablets delivered to the door within an hour of speaking to someone at the prescribing team – it was a fantastic service,” she added.
Amy thinks the tablets made a difference to how she felt with the virus.
“If I hadn’t started taking them then I genuinely think I would have ended up hospitalised, they made a huge difference within 24 hours,” she added.
What is anti-viral medicine?
The tablet used in this trial is called molnupiravir – a pill originally developed to treat flu.
It was developed by the US drug companies Merck, Sharp and Dohme (MSD) and Ridgeback Biotherapeutics.
It is the first antiviral medication for Covid which can be taken as a pill rather than injected or given intravenously.
Dr Andrew Carson-Stevens, a GP and the principal investigator of the Panoramic study team in Wales, said it can reduce the effects of the virus.
“The drug is absorbed by Covid infection cells and then blocks the virus replicating,” he said. “This means that the viral load should remain low, which reduces the risk of serious disease.”
The anti-viral is expected to be equally effective against all coronavirus variants.
Dr Carson-Stevens warned that vaccines and boosters were still the best way to protect ourselves, but that antiviral drugs will be “gamechangers” in the pandemic.
As part of the trial, the pills will need to be taken twice a day and within five days of symptoms starting.
Am I eligible to get them?
In Wales, anyone over 50 can take part, or those who are 18-49 with an underlying health condition, with a positive Covid-19 test (PCR or LFT) and symptoms for fewer than five days.
Those at the highest risk of severe effects of Covid, such as those with cancer or a rare neurological condition such as Huntington’s disease should have been written to by their health board.
These people will be able to access the tablets without being part of the trial.
People with a positive Covid test you will receive a text from Health and Care Research Wales with a link to the study website.
If you do a test at home that is positive then you can register on the website.
Prof Kerry Hood, director of the Centre for Trials for Research at Cardiff University, started planning for this last summer.
“We will soon be starting to get results from the trail as we follow people for 28 days who take part and the trial started on 8 December,” she said.
She said a “One Wales Approach” was important to make sure that everyone had the opportunity to take part wherever they live.
Anyone who has a positive PCR will receive a text telling them about the trial and if they are eligible, a courier will deliver the tablets within 24 hours to their door.
She added: “It’s all done remotely, which means it’s not centred in a specific location like a hospital, so no one in Wales will be excluded due to issues like transport.”
Prof Hood said future plans for the trial include testing new drugs when approved, reaching those in care homes and seeing if anti-virals can lower transmission of the virus.
A Welsh government spokesman said: “The booster programme remains our most effective tool in reducing the impact of coronavirus.
“For most people antivirals are less effective than vaccination, that is why we are working with Health and Care Research Wales to support the UK-wide antiviral study and other clinical trials of medicines that may be of benefit in the treatment of COVID-19, before they are made more widely available.”