Although the infection rate in Africa has generally remained lower than in other continents, the low levels of inoculation increase the risk that new variants could emerge as the virus continues to circulate, experts said.
The W.H.O. has reliable data for 52 of the 54 African countries — Eritrea has supplied no statistics, and Tanzania only partial figures. About half have vaccinated less than 3 percent of their residents, including many of the most populous, like Nigeria, Congo, Kenya and Uganda.
The continent has suffered from vaccine shortages, made worse by a shortfall in deliveries from the global vaccine-sharing initiative, Covax. Wealthy countries that pledged to support the initiative have given it only a fraction of the promised doses.
The majority of Covid-19 shots administered around the world so far have been given in high-income and upper-middle-income countries. The pattern has been the same in Africa, where countries with more advanced economies, including South Africa, Morocco and Botswana, have outpaced their poorer neighbors.
“In Africa, the major issue has been a supply issue rather than a demand issue,” Dr. Mihigo said, adding that vaccine hesitancy has been an issue “here and there.” The W.H.O. said it was working to identify bottlenecks in countries where limited technical capacity to deliver vaccines has hampered inoculation campaigns.