A health-care worker shows a syringe to a woman after injecting her with a dose of the Sinovac vaccine at a COVID-19 vaccination point for seniors in Duque de Caxias, Brazil, on March 24, 2021. #

A university teacher takes a selfie as she is vaccinated against COVID-19 during a vaccination campaign at the Sports Center of the University of Seville in Seville, Spain, on February 24, 2021. #

People receive the Pfizer-BioNTech COVID-19 vaccine during opening day of the Community Vaccination Site, a collaboration between the City of Seattle, First & Goal Inc., and Swedish Health Services, at the Lumen Field Event Center in Seattle, Washington, on March 13, 2021. #

Municipal health workers travel on a boat along the banks of the Solimões River, where Ribeirinhos ("river dwellers") live, to administer the AstraZeneca-Oxford vaccine, in Manacapuru, Amazonas state, Brazil, on February 1, 2021. #

Employees work on the production line of CoronaVac, Sinovac Biotech's vaccine against COVID-19, at the Butantan biomedical production center in Sao Paulo, Brazil, on January 14, 2021. #

A vehicle carrying a COVID-19 vaccination team crosses a flooded bridge in Zvimba Rural District, near Jari Village, where they vaccinated health workers on February 23, 2021, near Chinhoyi, Zimbabwe. #

Nurses Gokalp Balli (left) and Bilge Koc, from the Gevas Public Health Center, vaccinate 74-year-old Basra Payza with the Sinovac Coronavac vaccine during a house call in the village of Daldere on February 12, 2021, in Van, Turkey. Medical teams across the country have been working house to house to administer the COVID-19 vaccine to elderly and vulnerable citizens. #

Doctor Akay Kaya (right) and nurse Yildiz Ayten, from the Bahcesaray public hospital, arrive in the remote village of Guneyyamac, in eastern Turkey, to vaccinate residents aged 65 or older with the Sinovac CoronaVac COVID-19 vaccine on February 15, 2021. #

A woman receives a COVID-19 vaccine as part of the vaccination campaign for health workers and people over 65 years old at Muyumba Health Center in Kigali, Rwanda, on March 5, 2021. #

Rosie Gibuma receives the AstraZeneca COVID-19 vaccine at the Boigu community center, administered by Queensland Health nurse Ruth Ferguson on March 24, 2021, in Boigu Island, Australia. COVID-19 vaccinations have started ahead of schedule in the Torres Strait, with health authorities bringing forward the coronavirus vaccine rollout amid growing concerns of an outbreak in the remote region as nearby Papua New Guinea grapples with a COVID-19 outbreak. #

In an aerial view from a drone, motorists are seen lined up to receive COVID-19 vaccines at a mass-vaccination site at Dodger Stadium, with the downtown Los Angeles skyline in the background, on January 22, 2021, in California. #

Registered Nurse Ebony Thomas administers a Moderna COVID-19 vaccine to Cecilia Onwytalu, 89, at Kedren Community Health Center, in South Central Los Angeles, California, on February 16, 2021. #

A nurse draws up a vaccine dose as members of the public receive their COVID-19 vaccinations at Lichfield Cathedral, Staffordshire, on February 26, 2021, in Lichfield, England. #

One-hundred-year-old Ellen Prosser, known as Nell, receives the Oxford-AstraZeneca COVID-19 vaccine from Dr. Nikki Kanani at the Sunrise Care Home in Sidcup, southeast London, on January 7, 2021. #

Dr. Mayank Amin administers the Pfizer-BioNTech COVID-19 vaccine to Helen Pepe, 94, at a clinic run by Skippack Pharmacy in Collegeville, Pennsylvania, on March 7, 2021. #

A nurse with the Italian army's mobile health team gives the Pfizer-BioNTech COVID-19 vaccine to a man as part of the home-vaccination plan for homebound people in the Molise region in Isernia, Italy, on March 28, 2021. #

Guarani indigenous chief Jurema Nunes receives a CoronaVac vaccination shot from nurse Rosane das Neves during a COVID-19 vaccination campaign at the Aldeia Mata Verde Bonita on January 20, 2021, in Marica, Brazil. #

Health-care workers monitor newly vaccinated Thai people for adverse reactions to the COVID-19 vaccine at the Bang Khae Market on March 17, 2021, in Bangkok, Thailand. #

A health-care worker administers a dose of the Pfizer-BioNTech COVID-19 vaccine to a Palestinian man at the health ministry in the West Bank city of Nablus, on March 21, 2021. #

A woman receives one of the country's first coronavirus vaccinations, using the AstraZeneca vaccine manufactured by the Serum Institute of India and provided through the global COVAX initiative, at Yaba Mainland hospital in Lagos, Nigeria, on March 12, 2021. #

The Azul airline aircraft, which transported Oxford-AstraZeneca vaccines from Sao Paulo to Rio de Janeiro, arrives at the Tom Jobim International Airport on January 22, 2021, in Rio de Janeiro, Brazil. Brazil's Health Minister Eduardo Pazuello accompanied the arrival of 2 million imported doses of the vaccine, coming from India. #

Leonidas de Jesus Gonzalez, 102, kisses a nurse's hand before receiving the Sinovac vaccine in a nursing home as part of the vaccination plan against COVID-19 at Hogar San Jose on February 25, 2021, in Medellin, Colombia. #

Jim Edelman takes a selfie to send to his kids after receiving a dose of the Johnson & Johnson COVID-19 vaccine at an event put on by the Thornton Fire Department on March 6, 2021, in Thornton, Colorado. #

A driver gives a thumbs-up as his passenger is vaccinated against COVID-19 by a health-care worker at a drive-through site at Tropical Park in Miami, Florida, on January 13, 2021. #