The vaccine achievement comes as the US approaches 600,000 deaths from the pandemic, the highest death toll in the world.
According to the latest data from the Centers for Disease Control and Prevention, the fifty per cent of adults milestone is equivalent to more than 129 million people.
Just under 74 per cent of the population over 65 years old is now fully vaccinated, as is 47 per cent of the population over the age of 12 – those currently eligible for the vaccine, as younger children are not.
An impressive 61.6 per cent of adults have received at least one dose of a vaccine against Covid-19.
On 5 May, the Biden administration announced a goal of vaccinating 70 per cent of US adults with at least one dose of a Covid-19 vaccine and for 160 million adults to be fully vaccinated by 4 July.
Despite the safety of the vaccines, there is still some hesitancy among segments of the population, and the government and its surrogates are working hard to soothe fears about side effects.
At the same time, companies, cities, and states are rolling out incentive schemes to encourage uptake. These have included everything from free beer, donuts, and fries, to scholarships, lottery, tickets, and free passes to leisure activities.
The Federal Emergency Management Agency has also mobilised pop-up clinics in rural areas and tens of thousands of pharmacies now offer walk-in appointments.
It is hoped that at a point during the summer, the US will reach the elusive herd immunity stage from the virus at which point effective widespread transmission is disrupted, stopping or slowing the spread of the disease.
It is believed that between 70 and 85 per cent of the population should be immunised either by vaccination or previous infection for this to occur.
Since the first cases of Covid-19 were recorded in the US in early 2020, there have been 33 million confirmed cases, and 587,830 officially recorded deaths.