Omicron in S. Africa appears relatively mild. That might not be the case everywhere, continental CDC says.

A recent analysis of some 161,000 covid cases in South Africa between October and early December indicated that omicron was 80 percent less likely to lead to hospitalization than the delta variant and that for patients who were hospitalized, the risk of severe illness was 30 percent lower.

The paper, published Wednesday by South Africa’s National Institute for Communicable Diseases, has not been peer-reviewed. But it comes amid other signs that the omicron wave in South Africa has quickly started subsiding.

The country logged over 21,000 new infections on Thursday, according to government data, down from nearly 38,000 on Dec. 12. As of early this week, positivity rates have fallen, along with stress on testing infrastructure.

Nkengasong also noted that South Africa, where the median age is 28, has a relatively young population. That is a full decade lower than the median age in the United States, according to Census Bureau data.

And Salim Abdool Karim, a top infectious-disease scientist from the country, recently told The Washington Post that South Africans with omicron are more likely to produce a robust antibody response since over 70 percent of the country’s residents have been infected by non-omicron coronavirus variants.

While South Africa’s vaccination rate — about 26 percent of its population has been fully immunized, according to Our World in Data — is lower than the global average, it is higher than the immunization rate for the African continent.

Nkengasong, who leads the African Union’s public health body, used his Thursday briefing to urge governments of the 55-member bloc to ramp up vaccination programs. The aim, he said, is fully immunizing 70 percent of the continent’s eligible population by the end of next year. The figure is currently 10 percent.

“Our campaign should be aiming at pushing out people who have not received their first dose to receive their first dose, [pushing] out people who have received their first dose to get their second dose, and for the eligible population to get their booster dose,” he said. “It’s a collective action that we should really encourage everyone.”

Data from elsewhere is being closely watched in the United States, where the omicron variant has become dominant, according to U.S. CDC estimates from Monday. A nationwide surge in case numbers ahead of the holiday season has led to disappointment and fatigue as the global pandemic enters its third year.

There are also flickers of optimism from Britain, where the omicron variant pushed the daily case count past 100,000 for the first time Wednesday. Early research from Scotland, which has not been peer-reviewed, found that people infected with the omicron variant were almost 60 percent less likely to enter the hospital than those with delta. Another study from England spelled out a similar trajectory.

The scientists qualified the “encouraging” conclusions by warning of the reduced efficacy of vaccines against infection. (The makers of the Pfizer-BioNTech and Moderna shots say that booster doses appear to restore significant protection against infection.) The British researchers also noted that the highly transmissible nature of omicron could still overwhelm hospitals.

But Karim, the South African epidemiologist, offered a more upbeat outlook in a recent interview. “Now we’re going down, right back down,” he said, adding that he expected “every other country, or almost every other, to follow the same trajectory.”

Max Bearak in Nairobi contributed reporting to this article.

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