The study by Discovery Health, South Africa’s largest health insurer, of 211,000 positive coronavirus cases, of which 78,000 were attributed to omicron, showed that risk of hospital admissions among adults who contracted covid-19 was 29 percent lower than in the initial pandemic wave that emerged in March 2020.

However, the study, released Tuesday, found that the vaccine from U.S. pharmaceutical giant Pfizer and German partner BioNTech provided just 33 percent protection against infection, much less than the level for other variants detected in the country. At the same time, the vaccine provided 70 percent protection in fully vaccinated individuals against severe complications that would require a patient to be hospitalized, the study found, calling that “very good protection.”

Children appear to have a 20 percent higher risk of hospital admission with complications during the fourth wave of coronavirus cases than during the first, despite a very low absolute incidence, the study found.