World Health Organisation emergencies head Mike Ryan has urged countries to use extreme caution when lifting coronavirus restrictions so as "not to lose the gains you've made" as the global death toll passed four million.
Ryan's comments come as England prepares to end many COVID-19 restrictions on July 19, European countries ease travel curbs and Indian states relax their lockdowns despite accelerating infections with the Delta variant worldwide.
Ryan said that while every country must decide for itself, individuals including the unvaccinated must take responsibility to protect themselves and others to keep hospitals from being overwhelmed by another pandemic wave.
"The idea that everyone is protected, and it's 'Kumbaya' and everything goes back to normal, I think right now is a very dangerous assumption anywhere in the world, and it's still a dangerous assumption in the European environment," he told reporters during a meeting from Geneva.
"We would ask governments at this moment not to lose the gains you've made."
Ahead of reopening, UK Prime Minister Boris Johnson has said the epidemiological situation may be aided by the arrival of summer and school holidays.
Ryan said he believed UK scientists were "very aware of the threat represented by variants, especially the Delta variant" and would open cautiously.
The WHO also urged countries that are vaccinating 12- to 15-year-old children to instead donate doses to the vaccine sharing program COVAX to improve access for healthcare workers and the elderly in low-income countries.
"It's not the pediatric population that is suffering the most," WHO vaccine expert Ann Lindstrand said.
"It is the adults, it is the medical risk groups."
WHO director-general Tedros Adhanom Ghebreyesus said on Wednesday the global coronavirus death toll had broken the four million barrier.
"We have just passed the tragic milestone of four million recorded COVID-19 deaths, which likely underestimates the overall toll," Tedros said.
"At this stage in the pandemic, the fact that millions of health and care workers have still not been vaccinated is abhorrent."
Global COVID-19 infections have continued to increase for the second consecutive week, with more than 2.6 million recorded cases, 3 per cent more than the previous week.
In the period from 28 June to 4 July, roughly 54,000 deaths by COVID-19 were reported, 7 per cent less than the previous week and the lowest figure since October 2020.
However, infection rates ballooned across the board, with the exception of the Americas, which alongside Southeast Asia is also spared from an increase in the number of deaths reported worldwide, in comparison to the previous week.
The African continent is one of the most affected due to a lack of vaccines, as its virus-linked deaths soared by 23 per cent and infections grew by 15 per cent.
In Europe, contagion increased by 30 per cent while deaths rose by 6 per cent.
The countries with the highest infection rates in the past week were Brazil, India, Colombia, Indonesia and the United Kingdom.