A health worker in Mexico City prepares a Sputnik V dose during a mass vaccination effort against COVID-19. A new study in Mexico shows that non-mRNA vaccines like the Russian version can be as effective as mRNA vaccines like Pfizer if the patient has previously been infected with SARS-CoV-2. Luis Barron/Eyepix Group/Barcroft Media via Getty Images hide caption
A Cuban industrial complex prepares to start production of one of the country's newly developed COVID vaccines. Yander Zamora/Pool/AFP via Getty Images hide caption
With its new COVID-19 vaccine, Pfizer and BioNTech are hoping to get ahead of worsening effects of omicron as well as any new variants. Jonas Roosens/Belga Mag/AFP via Getty Images hide caption
The Glorietta Mall in Makati City in metro Manila was transformed into a mass vaccination site on December 1 during a government-sponsored campaign to increase the number of people vaccinated across the country. Ella Mage/NPR hide caption
Safeway pharmacist Shahrzad Khoobyari administers a Pfizer-BioNTech COVID-19 booster shot into the arm of Norman Solomon in San Rafael, Calif., in October. Justin Sullivan/Getty Images hide caption
Pharmacist LaChandra McGowan prepares a dose of the Pfizer COVID-19 vaccine at a clinic operated by DePaul Community Health in New Orleans in August. Soon, children ages 5 to 11 could be eligible for Pfizer shots. Mario Tama/Getty Images hide caption
A health care worker administers a Pfizer-BioNTech COVID-19 vaccine Thursday at Life of Hope Center in New York City. Michael M. Santiago/Getty Images hide caption
A health care worker prepares a dose of the Moderna COVID-19 vaccine during a clinic held at the Watts Juneteenth Street Fair in the Watts neighborhood of Los Angeles. Patrick T. Fallon/AFP via Getty Images hide caption
Janet Gerber, a health department worker in Louisville, Ky., processes boxes containing vials of the Johnson & Johnson COVID vaccine in March. Jon Cherry/Getty Images hide caption
A nurse prepares a dose of the Moderna COVID-19 vaccine at a San Antonio senior center in March. A panel of advisers to the Food and Drug Administration will meet Thursday to review Moderna's booster shot. Sergio Flores/Getty Images hide caption
One thorny issue facing President Biden at the United Nations: the defense deal he announced with Australia and the U.K., which left France so angry it pulled its ambassador from Washington, D.C. Win McNamee/Getty Images hide caption
A syringe with the Pfizer COVID-19 vaccine is prepared at a mobile vaccine clinic in Santa Ana, Calif., in August. An international group of scientists is arguing the average person doesn't need a COVID-19 booster yet — an opinion that highlights the intense scientific divide over the question. Jae C. Hong/AP hide caption
A third shot of the Moderna vaccine boosts protection across age groups, notably in older adults, the company says. Juana Miyer/Long Visual Press/Universal Imag hide caption
A COVID-19 vaccine dose is prepared at a pharmacy in Baton Rouge, La., on Aug. 17. About 14 million people received their first dose of a COVID-19 vaccine in August. Mario Tama/Getty Images hide caption
Medics in Jerusalem transfer a COVID-19 patient to Hadassah Hospital Ein Kerem. Many hospitals in Israel are at full capacity following a sharp increase in coronavirus infections. Menahem Kahana/AFP via Getty Images hide caption