- A study examined the differences in severe disease and hospitalisation between the Delta and Omicron phases.
- When the Omicron phase arrived, more people had been vaccinated.
- Vaccination is linked to a smaller risk of severe illness and need for intensive care.
A new study found that vaccinated adults experienced less severe Covid-19 than unvaccinated adults and were less likely to land in intensive care during the Omicron-driven wave.
The Centers for Disease Control and Prevention (CDC) compared the clinical features and outcomes of hospitalised Covid-19 patients in the US during the Delta and Omicron phases.
The researchers abstracted data from electronic health records of patients above 18 in one academic hospital. They used the data of 339 patients from the Delta period and 737 patients from the Omicron wave.
Vaccination data showed that a higher proportion of adults had been vaccinated during the Omicron wave than during the Delta wave.
Less severe diseases
The study results show that fewer patients were being admitted for severe Covid-19 and fewer patients required intensive care unit (ICU) admission and invasive mechanical ventilation.
The results also show that fewer people died in hospitals during the Omicron wave, with a 3.4% death rate compared to 10.6% during the Delta surge.
In the Omicron period, it was found that vaccinated patients had a lower likelihood of ICU admission and, among adults aged above 65 years, there was a lower likelihood of death while in the hospital.
Furthermore, people who had taken their booster vaccine had the lowest chance of ICU admission and death.
The study also found that about 20% of Omicron-period hospitalisations among adults with a positive SARS-CoV-2 result were driven by non–Covid-19 conditions, which might be attributed to both high Covid-19 community transmission and high population vaccination coverage.
"These findings support the continued importance of Covid-19 vaccination, including booster doses, in mitigating the risk of severe illness associated with SARS-CoV-2 infection," the authors wrote.