Why Severe COVID-19 Cases Decrease Despite Omicron Surge [Reading Science]

Qatar Research Team: "Natural Immunity Developed After Infection Continues to Provide Protection Against Severe Disease"

On the 16th, medical staff are caring for a patient in the intensive care unit of Pakae Hospital, a COVID-19 dedicated hospital in Pyeongtaek-si, Gyeonggi-do. Photo by Moon Honam munonam@

[Asia Economy Reporter Kim Bong-su] Patients who have recovered from COVID-19 infection have been found to have strong protection against early viruses before the Omicron variant for up to 16 months, continuously providing prevention against severe illness. This research result suggests that although reinfection rates are soaring worldwide due to Omicron and its subvariants, hospitals in various countries may not be overwhelmed again with critically ill patients.

According to the international academic journal Nature on the 16th, a research team from Cornell University in Qatar recently published these findings on the medical preprint site MedRxiv. The team utilized data collected by the Qatar health authorities on COVID-19 patients from February 28, 2020, to June 5 of this year to obtain these results. Specifically, during this period, they investigated previous infections and vaccination status among COVID-19 infected individuals. It was found that people who were unvaccinated and infected with pre-Omicron variants such as Alpha and Delta had an average of 85.5% protection against the same type of variant between 4 to 16 months after recovery. This protection peaked at 90.5% seven months after the first infection and decreased to about 70% after 16 months.

In particular, the prevention effect against severe illness was strong and showed greater durability compared to protection against infection. The prevention effect against severe illness remained close to 100% up to 14 months after the initial infection and did not decrease over time. In contrast, protection against the Omicron variant was low at 38% for six months after recovery and was expected to drop to 10% after 15 months.

These research results do not imply that people who have recovered from COVID-19 without vaccination no longer need to get vaccinated. Rice Aburadad, a researcher at Weill Cornell Medicine in Doha, Qatar, stated, "It is clear that individuals with hybrid immunity from both vaccination and infection receive much stronger protection against the virus."