Britain's Prime Minister Boris Johnson attends a media briefing in Downing Street, London, Monday, June 14, 2021. Johnson has confirmed that the next planned relaxation of coronavirus restrictions in England will be delayed by four weeks until July 19 as a result of the spread of the delta variant. In a press briefing Monday, Johnson said he is “confident that we won’t need more than four weeks” as millions more people get fully vaccinated against the virus, which could save thousands of lives. (Jonathan Buckmaster/Pool Photo via AP)

Bravo, a Labrador Retriever, sits in front of a sample of human sweat after detecting the COVID-19 coronavirus at a mobile canine unit in Bangkok, Thailand, Thursday, June 17, 2021. Thailand has deployed a canine virus detection squad to help provide a fast and effective way of identifying people with COVID-19 as the country faces a surge in cases, with clusters found in several crowded slum communities and large markets. (AP Photo/Sakchai Lalit)

A man wearing a face mask walks with an infant on a sling in Imphal, India, Thursday, June 17, 2021. (AP Photo/Yirmiyan Arthur)

Heidi Parker, executive director of Immunize Nevada, helps to announce a COVID-19 vaccine incentive program, "Vax Nevada Days," in the Twitch Lounge at Allegiant Stadium on Thursday, June 17, 2021, in Las Vegas. The program will automatically enter Nevadans who have had at least one dose of the COVID-19 vaccine into a weekly drawing that offers $5 million in cash and prizes, including a $1 million grand prize. (Ellen Schmidt/Las Vegas Review-Journal via AP)

People enjoy a ride at Cinecitta World amusement park in the outskirts of Rome in the day of its reopening, Thursday, June 17, 2021. Amusement parks have been closed since Oct. 25 2020, when Italy's second national lockdown started. (AP Photo/Alessandra Tarantino)

An Indian woman wearing face mask as a precaution against the coronavirus speaks on mobile phone standing in front of a Peacock graffiti on a wall in Hyderabad, India, Thursday, June 17, 2021. (AP Photo/Mahesh Kumar A.)

People walk by posters to promote the Olympic Games planned to start in the summer of 2021, in Tokyo, Wednesday, June 16, 2021. (AP Photo/Koji Sasahara)

FILE - In this Jan. 20, 2021, file photo, a Russian medical worker, right, administers a shot of Russia's Sputnik V coronavirus vaccine to a patient in a vaccination center in Moscow, Russia. Authorities in four Russian regions this week made COVID-19 vaccinations mandatory for those working in certain sectors of the economy in a bid to boost Russia’s slow immunization rates as coronavirus infections continue to soar. Moscow was the first to announce the measure on Wednesday, June 16, 2021 and the surrounding Moscow region, the Siberian region of Kemerovo and the far eastern Sakhalin promptly followed suit. (AP Photo/Pavel Golovkin, File)

Xavier University of Louisiana President Reynold Verret testifies during a Senate Health Education, Labor, and Pensions Committee hearing on Capitol Hill in Washington, Thursday, June 17, 2021, to examine the COVID-19 response and recovery and how to support students in higher education and safely return to campus. (AP Photo/Susan Walsh)

People enjoy a ride at Cinecitta World amusement park in the outskirts of Rome in the day of its reopening, Thursday, June 17, 2021. Amusement parks have been closed since Oct. 25 2020, when Italy's second national lockdown started. (AP Photo/Alessandra Tarantino)

Slovakian players celebrate at the end of the Euro 2020 soccer championship group E match between Poland v Slovakia at the Saint Petersburg stadium in St. Petersburg, Russia, Monday, June 14, 2021. (Evgenya Novozhenina/Pool via AP)

FILE - In this Jan. 7, 2021, file photo, a registered nurse tends to a COVID-19 patient as another puts on her protective gear in Orange, Calif. With more than 600,000 Americans dead of COVID-19 and questions still raging about the origin of the virus and the government's response, a push is underway on Capitol Hill and beyond for a full-blown investigation of the crisis by a national commission like the one that looked into 9/11. (AP Photo/Jae C. Hong, File)

FILE- This Jan. 7, 2021, file photo, shows the Curevac company headquarters in Tuebingen, Germany. German vaccine maker CureVac said Wednesday, June 16, 2021, that interim data from late-stage testing of its coronavirus shot show a comparatively low effectiveness in protecting people against COVID-19. (Sebastian Gollnow/dpa via AP, File)

A preacher holds the bible while praying and worshipping to a group of followers atop a mountain in Harare, in this Friday, May 28, 2021 photo. As virus cases surge in the worlds poorest countries, there is growing sense of looming danger for millions of the unvaccinated,especially those who toil in the informal sector,living hand to mouth and inevitably pay cash when in health emergencies. (AP Photo/Tsvangirayi Mukwazhi)

Medical staff wearing protective equipment attend to patients affected by the COVID-19, at the Intensive Care Unit (ICU) of the Machakos County Level-5 hospital in Machakos, Kenya, Thursday June 17, 2021. Africa, whose 1.3 billion people account for 18% of the global population, has received only 2% of all vaccine doses administered globally. (AP Photo/Brian Inganga).

A man wearing a face mask rides a bicycle on a street in Imphal, India, Thursday, June 17, 2021. (AP Photo/Yirmiyan Arthur)

FILE - In this May 11, 2021, file photo, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during hearing on Capitol Hill in Washington. The United States is devoting more than $3 billion to advance development of antiviral pills for COVID-19, according to an official briefed on the matter. The pills, which would be used to minimize symptoms after infection, are in development and could begin arriving by year's end, pending the completion of clinical trials. (Jim Lo Scalzo/Pool Photo via AP, File)

A sign points the way to administrate a dose of the Pfizer COVID-19 vaccine at London Middle School in Wheeling, Ill., Friday, June 11, 2021. After nearly 15 months of shutdowns, limited capacity and sheltering at home, the State of Illinois, including Chicago, fully reopened today. Businesses still can have their own rules for capacity, masks and social distancing. Masks are still required on public transportation and in airports, schools and hospitals. (AP Photo/Nam Y. Huh)

FILE - In this March 11, 2021 file photo, a group of young people wearing face masks chat at a viewpoint overlooking Lisbon's old center. Travel in and out of the Lisbon metropolitan area is to be banned over coming weekends as Portuguese authorities respond to a spike in new COVID-19 cases in the region around the capital, officials announced Thursday, June 17. (AP Photo/Armando Franca)

FILE - In this file photo taken June 6, 2021, first lady Jill Biden, center left, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, Choose Healthy Life public health navigator Linda Thompson and Choose Healthy Life Founder Debra Fraser-Howze, far right, speak to a person as they visit a vaccine clinic at the Abyssinian Baptist Church in the Harlem neighborhood of New York. The church is part of Choose Healthy Life, a national initiative involving Black clergy, United Way of New York City and others, that has just been awarded a $9.9 million U.S. Department of Health and Human Services grant to expand vaccinations and provide screening and other health services in churches. (AP Photo/Craig Ruttle, File)

Sen. Susan Collins, R-Maine, left, and Sen. Lisa Murkowski, R-Alaska, talk during a Senate Appropriations Committee hearing to examine proposed budget estimates and justification for fiscal year 2022 for the Department of Defense in Washington on Thursday, June 17, 2021. (Caroline Brehman/Pool via AP)

People crosses the Trocadero plaza near Eiffel Tower in Paris, Thursday, June 17, 2021. France on Wednesday eased several COVID-19 restrictions, with authorities saying it's no longer always mandatory to wear masks outdoors, and halting an 8-month nightly coronavirus curfew this weekend. (AP Photo/Michel Euler)