A woman walks past a public information sign in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday. (Photos: Jon Super/Xinhua)

A woman walks past a sign for a COVID-19 test center in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

A woman walks past a COVID-19 home testing kit collection center in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

A man wearing a face mask walks on a street in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

A sign for a COVID-19 test center is seen on a street in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

Signs reminding people to wear masks are seen outside a market in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

(210521) -- BLACKBURN, May 21, 2021 (Xinhua) -- People wait to enter a COVID-19 vaccination center in Blackburn, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.

People register outside a COVID-19 vaccination center in Bolton, Britain, on May 21, 2021. Another 2,829 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 4,457,923, according to official figures released Friday.