On July 19, the UK eased almost all of its coronavirus restrictions. Mask-wearing is no longer mandatory. There are no limits on the number of people who can meet indoors or outdoors. Nightclubs are now open.

Is the UK close to herd immunity?

A major basis for the UK to make the decision is that the majority of people in the country have been vaccinated against COVID-19. Official data from the government showed that as of July 18, 54 percent of the UK's total population has been fully vaccinated, and more than 69 percent have received one dose of vaccine.

By relaxing most of the preventive restrictions, the UK government seemed to be reverting to a "herd immunity approach."

"Herd immunity," also known as "population immunity," is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through natural infection, according to the World Health Organization.

Depending on how contagious a disease is, about 50 to 90 percent of a population needs to acquire immunity before herd protection can be achieved, according to Johns Hopkins University.

For example, if 70 percent of a population is immune to a virus, seven out of every 10 people who are exposed to a source of infection won't get sick or spread the disease any further.

But don't think of it as some sort of fixed "magic threshold," especially for a new virus. The number can go up or down when the virus mutates and people change the way they interact with each other.

Even above a "herd immunity threshold," people who are not immune can still get infected.

Usually, the higher the immunity rate of a population is, the slower the virus transmits. That's why it's important to get as many people as possible inoculated.

The "herd immunity threshold" of the coronavirus remains unclear, but experts have said that at least 70 to 80 percent of the global population needs to be vaccinated to achieve that.

Although the UK has a relatively high vaccination rate of more than 54 percent, there have been more than 30,000 daily new infections in the country over the past week, data from Johns Hopkins University showed. That clearly shows the transmission of the coronavirus is far from being cut off.

In a letter published on the prestigious medical journal The Lancet earlier this month, which was backed by more than 120 international scientists, the authors wrote that the ease of the restrictions in the UK means the government is allowing immunity to be achieved by vaccination for some people but by natural infection for others, predominantly young people.

'A dangerous and unethical experiment'

While Monday has been hailed as "freedom day" in the country, scientists have raised deep concerns about the move, calling it "unethical and premature." 

They warned that the British government is embarking on a "dangerous and unethical experiment."

UK Health Secretary Sajid Javid has said that daily cases could reach 100,000 per day over the summer months, BBC reported.

He confirmed on Saturday that he tested positive for the coronavirus and was suffering "very mild" symptoms, despite the fact that he had received two doses of vaccine.

One of the major concerns raised by scientists in the letter is that unmitigated transmission of the virus will disproportionately affect unvaccinated children and young people who have already suffered greatly.

Besides, preliminary modelling data suggest the strategy provides fertile ground for the emergence of vaccine-resistant variants, which would place all at risk, including those already vaccinated, within the UK and globally, they wrote.

Deepti Gurdasani, a British clinical epidemiologist, said on Twitter that "the world is watching the current avoidable crisis unfold in the UK."