Omicron Resists Pfizer Vaccine but Causes Less Severe Disease

Compared with previous coronavirus variants, omicron appears to cause less severe illness, but is more resistant to the Pfizer vaccine, researchers at South Africa's largest health insurer report.

The team at Discovery Health analyzed 211,000 positive COVID-19 cases during the country's fourth wave, including 78,000 attributed to omicron. The researchers found that during the latest wave, the risk for hospital admission among adults with COVID-19 was 29 percent lower than in the first pandemic wave that began in March 2020. However, the Pfizer vaccine provided just 33 percent protection against infection with omicron, a much lower rate than against other variants, according to the study. The vaccine did give 70 percent protection against severe complications that would require hospitalization, which is "very good protection," the researchers said.

The South African researchers also found that children had a 20 percent higher risk for hospital admission with complications during the fourth wave than during the first wave.

"What is encouraging at this stage is a flatter trajectory of hospital admissions indicating likely lower severity of this wave," Ryan Noach, Discovery'chief executive, said during a news briefing. But earlier, he warned that South Africa's health care system could still be overwhelmed as omicron continues to evolve. "The omicron-driven fourth wave has a significantly steeper trajectory of new infections relative to prior waves," Noach said in a statement. "National data show an exponential increase in both new infections and test positivity rates during the first three weeks of this wave, indicating a highly transmissible variant with rapid community spread of infection."