A health care worker holds doses of J&J vaccines at the Gandhi Phoenix Settlement in Bhambayi township, South Africa, on Sept. 24. A study of the J&J booster shot in the country had promising results against the omicron variant. Rajesh Jantilal/AFP via 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
The vial of the Johnson & Johnson COVID-19 vaccine. The White House says Thursday that the U.S. will commit 17 million additional doses of the Johnson & Johnson vaccine to the African Union. Picture Alliance/dpa/picture alliance via Getty I hide caption
The CDC's new research found that those who were vaccinated were nearly five times less likely to get infected, 10 times less likely to get so sick they ended up in the hospital and 11 times less likely to die. Chandan Khanna/AFP via Getty Images hide caption
Bottles of the single-dose Johnson & Johnson COVID-19 vaccine await transfer into syringes for administering last month in Los Angeles. Frederic J. Brown/AFP via Getty Images hide caption
Boxes containing the Johnson & Johnson COVID-19 vaccine, developed by the company's Janssen Pharmaceuticals unit, are shown at a vaccination center in Los Angeles last week. Allen J. Schaben/Los Angeles Times via Getty Images hide caption
Bottles of the single-dose Johnson & Johnson Janssen COVID-19 vaccine await transfer into syringes for administering in March in Los Angeles. The CDC had called on Tuesday for a pause in administering the vaccine. Frederic J. Brown/AFP via Getty Images hide caption
Dr. Anike Baptiste receives a dose of J&J from nurse Mokgadi Malebye at a Pretoria hospital last February. South Africa is one of the countries that announced a pause on the J&J vaccine while more research is done into potential blood clots that occurred in younger women after getting the vaccine. Phill Magakoe/AFP via Getty Images hide caption
Boxes containing vials of the Janssen COVID-19 vaccine sit in a container before being transported to a refrigeration unit at Louisville Metro Health and Wellness headquarters on March 4 in Louisville, Ky. The FDA approved the third COVID-19 vaccine on Feb. 27. Jon Cherry/Getty Images hide caption
A health care worker holds a vial of the Johnson & Johnson COVID-19 vaccine at South Shore University Hospital in Bay Shore, N.Y., on Wednesday. Bloomberg/Bloomberg via Getty Images hide caption
The first box of Johnson & Johnson's COVID-19 vaccine departs from a facility in Shepherdsville, Ky., on Monday. The company is set to distribute its first 3.9 million doses across the U.S. this week. Timothy D. Easley/Getty Images hide caption
During remarks at the National Institutes of Health, President Joe Biden said his administration has secured enough Covid-19 vaccines to ensure the nation is on track to vaccinate 300 million Americans by mid-July. Evan Vucci/AP hide caption
After a small study raised concerns about the effectiveness of the AstraZeneca vaccine against the variant in South Africa, the country put its AstraZeneca vaccine plans on hold. "It is time, unfortunately, for us to recalibrate our expectation of COVID-19 vaccines," said Shabir Madhi, professor of vaccinology at the University of Witwatersrand, shown above at a vaccine trial facility. Jerome Delay/AP hide caption