Researchers at the Imperial College London published a report this weekend saying the Omicron variant of COVID-19 may be as virulent and severe as the Delta strain.
The study finds no evidence of Omicron having lower severity than Delta, judged by either the proportion of people testing positive who report symptoms, or by the proportion of cases seeking hospital care after infection,” said the research team led by Professor Neil Ferguson.
“The growth rates estimated for Omicron translate into doubling times of under 2.5 days, even allowing for the potentially slowing of growth up to 11th December,” the researchers wrote, noting that despite “strong evidence of immune evasion,” there was “moderate to high (55-80 percent) protection in people boosted with an mRNA vaccine.”
Moreover, the study — carried out by researchers at the Imperial College London, the Jameel Institute, MRC Centre for Global Infectious Disease Analysis and the World Health Organization (WHO) Collaborating Centre for Infectious Disease Modelling — estimated that the risk of reinfection with Omicron is 5.4 times greater than that of the Delta variant.
“Controlling for vaccine status, age, sex, ethnicity, asymptomatic status, region and specimen date, Omicron was associated with a 5.41 fold higher relative risk of reinfection compared with Delta,” the researchers wrote.
“We find strong evidence of immune evasion, both from natural infection, where the risk of reinfection is 5.41 fold higher for Omicron than for Delta, and from vaccine-induced protection.
“We find no evidence (for both risk of hospitalization attendance and symptom status) of Omicron having different severity from Delta, though data on hospitalizations are still very limited,” the researchers wrote.
A second author of the study, Professor Azra Ghani – also of the Imperial College London – added that governments need to make plans to contend with that possibility.
“Whilst it may take several weeks to fully understand this, governments will need to put in place plans now to mitigate any potential impact,” she said.
“The importance of delivering booster doses as part of the wider public health response,” she added, is underlined by the results of the study.
The findings were published December 16, 2021 by Imperial College London.