A registered nurse (RN) administers a nasal swab test for the coronavirus disease (COVID-19) at a Sameday Health clinic, as the Omicron coronavirus variant continues to spread after the Christmas holiday break, in the Brentwood neighborhood of Los Angeles, California, U.S. December 27, 2021.

Medical workers in protective suits collect swabs from residents at a nucleic acid testing site during a third round of mass testing following cases of the coronavirus disease (COVID-19) in Yuncheng's Jishan county, Shanxi province, China December 29, 2021. China Daily via REUTERS

People take a coronavirus disease (COVID-19) test at a pop-up testing site as the Omicron coronavirus variant continues to spread in Manhattan, New York City, U.S., December 27, 2021.

A woman takes a coronavirus disease (COVID-19) test at a pop-up testing site as the Omicron coronavirus variant continues to spread in Manhattan, New York City, U.S., December 27, 2021.

People wait in long lines for coronavirus disease (COVID-19) testing as the Omicron variant continues to spread in Memphis, Tennessee, U.S., December 28, 2021. Image used for illustrative purpose.

A pharmacy displays a sign notifying customers that there are no rapid antigen tests in stock, amidst the spread of the coronavirus disease (COVID-19) pandemic, in London, Britain, December 29, 2021.

A man takes a coronavirus disease (COVID-19) test at a pharmacy as COVID-19 infections rise, in Rome, Italy, December 29, 2021.

People queue to receive free lateral flow coronavirus disease (COVID-19) tests at a pharmacy, as the regional authorities re-stocked the supplies after the Christmas in Madrid, Spain December 28, 2021.

People queue in their cars for coronavirus disease (COVID-19) PCR testing at a clinic at North Ryde as the Omicron coronavirus variant continues to spread in Sydney, Australia, December 29, 2021. AAP Image/Mick Tsikas via REUTERS

A man reacts as a healthcare worker collects a swab sample from him to test for the coronavirus disease (COVID-19) at a railway station in Ahmedabad, India, December 29, 2021.

A man takes a coronavirus disease (COVID-19) test at a pharmacy as COVID-19 infections rise, in Rome, Italy, December 29, 2021.

A pharmacy displays a sign notifying customers about the unavailability of the rapid antigen tests, amidst the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, December 28, 2021.

A registered nurse (RN) sanitizes her hands between administering coronavirus disease (COVID-19) tests at a Sameday Health clinic, as the Omicron coronavirus variant continues to spread after the Christmas holiday break, in the Brentwood neighborhood of Los Angeles, California, U.S. December 27, 2021.

A coronavirus disease (COVID-19) antigen self-test kit is seen in this illustration photo, amidst the spread of the coronavirus disease (COVID-19) pandemic, in London, Britain, December 29, 2021. Image used for illustrative purpose.

A registered nurse (RN) is seen reflected in the mirror before administering a nasal swab test for the coronavirus disease (COVID-19) at a Sameday Health clinic, as the Omicron coronavirus variant continues to spread after the Christmas holiday break, in the Brentwood neighborhood of Los Angeles, California, U.S. December 27, 2021. Image for illustrative purposes.

A man wearing a protective face mask walks past the entrance to a vaccination centre is viewed through Christmas lights, amid the coronavirus disease (COVID-19) outbreak in Manchester, Britain, December 28, 2021.

A woman reacts as a healthcare worker collects a swab sample from her to test for the coronavirus disease (COVID-19) at a railway station in Ahmedabad, India, December 29, 2021.

A pharmacy displays a sign notifying customers that there are no rapid antigen tests in stock, amidst the spread of the coronavirus disease (COVID-19) pandemic, London, Britain, December 29, 2021.

A woman takes a coronavirus disease (COVID-19) test at a pharmacy as COVID-19 infections rise, in Rome, Italy, December 29, 2021.