The UK is reopening to vaccinated Americans, but will it last?

Beginning at 4 a.m. on Aug. 2, England will allow fully vaccinated travelers from the United States and the European Union to enter its borders without the need to quarantine.

The news was welcomed by the travel industry on both sides of the Atlantic. August would traditionally be one of the busiest travel months between the U.K. and the U.S. but has seen just a trickle of the usual traffic this summer thanks to tough restrictions for visitors to both countries.

But is this a permanent step toward normality?

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The United Kingdom celebrated its highly anticipated "Freedom Day" on July 19 when it removed most social distancing restrictions in England. The decision is being closely watched by other countries as it is considered somewhat of a gamble, as the world still grapples with the pandemic.

Prime Minister Boris Johnson is betting that the U.K.'s high vaccination rates have already permanently severed the link between COVID-19 infections and hospital admissions and that the worst of the pandemic is now over in the country. He has said that if England does not fully reopen now, in the middle of summer, when its population spends as much time outdoors in the fresh air as possible, the country might never do so.

Freedom Day arrived as the U.K. experienced worryingly high rates of new infections thanks to the highly infectious delta variant, thought to have originally been brought into the country from India, before India was placed on the U.K.'s travel ban "red" list.

Related: 5 things travelers need to know about the delta COVID-19 variant

You might be wondering why Freedom Day proceeded with such alarming new rates of cases. While new infections were being recorded in the tens of thousands by July 19, daily deaths from the virus remained in double digits compared with more than 1,000 per day during the January 2021 peak.

Infections are high, but deaths remain very low for a country of almost 68 million people.

Following a slight rise in new cases in the days following July 19, numbers have steadily fallen over the past week, from an average of 47,114 per day on July 21 to 29,703 on July 28 (on a seven-day average basis). This reduction comes as nightclubs are fully open and Brits socialize indoors and out, mostly restriction-free.

Boris Johnson has insisted Freedom Day is an irreversible change toward a post-pandemic life though the delta variant has already proven that nobody can predict the future of the pandemic. For now, scientific evidence continues to assure the British government that the vaccines, administered both in the U.K. and the U.S., do provide adequate protection against COVID-19 and each variant that has so far been identified, including the dreaded delta variant. This assurance has led to the U.K. welcoming those Americans who are fully vaccinated to visit without quarantining.

Related: The delta variant hasn't made a dent in US travel demand, airlines say

However, if the delta variant or even a new emerging variant does cause an unexpected spike in new infections in the United States, particularly in those who are fully vaccinated, then the U.K. may well suspend the quarantine waiver for Americans visiting the country for tourism purposes.

As seen with India earlier this year, a huge spike in new infections in the U.S. could even see the country moved to the U.K. government's dreaded red list, which would mean non-Brits are banned from entering the U.K. from the U.S. If this were to happen then any returning British citizens would be forced into expensive mandatory hotel quarantine for 10 days to reduce the spread of infections within the U.K.