South Africa Omicron study finds drop in vaccine protection, fewer hospitalized

Dec. 15, 2021

In some of the first real-world findings on Omicron's impact in South Africa, researchers found a drop in Pfizer vaccine effectiveness against hospitalization, but also a drop in hospitalizations, an early hint that infections might be less severe, according to a news report from the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota.

The South African research study covers the first 3 weeks of the Omicron outbreak in Gauteng province and was posted online in a preprint study from a team at Discovery Health, the country's largest insurer. They analyzed 211,000 PCR-positive test results from adults ages 18 and up, 41% of whom had received two doses of Pfizer-BioNTech COVID-19 vaccine.

Those who received two Pfizer doses were 70% less likely to be hospitalized, significantly lower than the 93% protection seen in South Africa's Delta (B1617.2) variant wave. Protection was slightly lower in the oldest age groups.

Regarding hospitalizations in general, the group said those infected with Omicron were 29% less likely to be hospitalized, compared to waves involving other variants. In a statement, Ryan Noach, MD, Discovery Health's chief executive officer, said the flatter trajectory of hospital admission in the Omicron wave that hints at lower severity could be confounded by high seroprevalence in South Africa's population, especially after its Delta wave.

Meanwhile, the WHO's African regional office said Omicron and Delta activity have resulted in an 83% increase in cases over the past week, though deaths aren't tracking as high as earlier surges and were down 19%. It added that cases are doubling every 5 days, the shortest period reported this year. Though South Africa's hospitalizations rose 67% in the past week, intensive care unit (ICU) occupancy remains low at 7.5%, with 14% of hospitalized patients needing oxygen.

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