Fewer hospitalisations due to Omicron, vaccines offer protection from severe disease, show studies

Only 4.9% of the patients who contracted the Omicron variant of coronavirus in South Africa’s Gauteng province had to be hospitalised for treatment. The number is significantly lower than the cases that led to hospitalisation in the region due to the Beta (18.9%) and Delta (13.7%) variants of the virus, findings of a study released by South African researchers on Wednesday has showed.

The study, yet to be peer-reviewed, focused on cases in the Gauteng province as the outbreak of the Omicron variant started in this region. This allowed the scientists to gather data about the new strain for a longer period.

The researchers compared data from the first four weeks of outbreaks of the Beta (November-December 2020), Delta (May 2021) and Omicron (November-December 2021) variants in Gauteng.

The study also showed that only 28.8% of the patients who were hospitalised after getting the Omicron infection suffered from severe symptoms. In contrast, 60.1% of the Beta variant cases and 66.9% of the Delta strain infections that led to hospitalisation resulted in deaths, or needed ventilation, oxygen support or admission to intensive care units.

However, in terms of absolute number of infections, the Omicron variant far surpassed the two other strains.

The scientists, however, noted that that the impact of the Omicron variant could be different in various countries, depending on factors such as co-morbidity among patients, vaccine coverage and the number of people who have had prior infections.

“...In some countries, Omicron-dominated waves began during a period of high Delta transmission whereas the Omicron-dominated fourth wave in South Africa began when Delta infections were very low,” the researchers observed.

Vaccination, prior infection may provide immunity against Omicron

Two other studies, conducted in South Africa and the United States, showed that T-cell responses among people who have been vaccinated against coronavirus, or have been infected by Delta and Beta strains offered protection against the Omicron variant.

T-cells are a type of white blood cell that determine the immune response in a person’s body against antigens, or foreign substances.

A study by researchers at University of Cape Town’s Institute of Infectious Disease and Molecular Medicine analysed people who have recovered from Covid-19 or have been inoculated by Pfizer-BioNTech and Johnson & Johnson vaccines.

They found that in 70%-80% of the T-cell responses provided protection from severe diseases caused by Omicron variant.

“While antibodies block infection, T-cells come in and kill infected cells, preventing the virus from growing and spreading more & causing worse disease,” Wendy Burgers, one of the authors of the study wrote on Twitter. “They can’t prevent you from getting infected, but they can minimise the damage that comes afterwards.”

Another study conducted by researchers at the La Jolla Institute for Immunology in United States’ California also had similar findings. In this case, the scientists studied people who have previously been infected with Covid, and those inoculated with the Moderna, Pfizer, or Johnson and Johnson vaccines.

They found that 83%-85% of the T-cell responses among these people held up against severe infections caused by the Omicron variant.

“We found similar behaviour, regardless of what vaccine that different people had taken,” Alessandro Sette, one of the authors of the study noted.

The new studies back the findings of earlier research that has been conducted on the incidence and severity of Omicron cases. Last week, three separate studies conducted across two continents had also concluded that people infected by the Omicron variant of the coronavirus were less likely to be hospitalised and suffer from severe symptoms. However, the Omicron variant was more likely to spread faster, the studies had found.