A just released report from The Imperial College London Covid-19 response team estimates that the risk of reinfection with the Omicron variant is 5.4 times greater than that of the Delta variant. This implies that the protection against reinfection by Omicron afforded by past infection may be as low as 19%.
Researchers estimate the growth and immune escape of the Omicron variant in England. They used data from the UKHSA and NHS for all PCR-confirmed SARS-CoV-2 cases in England who had taken a COVID test between November 29th and December 11th 2021.
Based on these results they estimate that the reproduction number (R) of Omicron was above 3 over the period studied.
Controlling for vaccine status, age, sex, ethnicity, asymptomatic status, region and specimen date, Omicron was associated with a 5.40 (95% CI: 4.38-6.63) fold higher risk of reinfection compared with Delta. To put this into context, in the pre-Omicron era, the UK “SIREN” study of COVID infection in healthcare workers estimated that prior infection afforded 85% protection against a second COVID infection over 6 months. The reinfection risk estimated in the current study suggests this protection has fallen to 19% (95%CI: 0-27%) against an Omicron infection.
Prof Neil Ferguson from Imperial College London said: “This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination. This level of immune evasion means that Omicron poses a major, imminent threat to public health.”
Researchers estimate the growth and immune escape of the Omicron variant in England. They used data from the UKHSA and NHS for all PCR-confirmed SARS-CoV-2 cases in England who had taken a COVID test between November 29th and December 11th 2021.
Based on these results they estimate that the reproduction number (R) of Omicron was above 3 over the period studied.
Controlling for vaccine status, age, sex, ethnicity, asymptomatic status, region and specimen date, Omicron was associated with a 5.40 (95% CI: 4.38-6.63) fold higher risk of reinfection compared with Delta. To put this into context, in the pre-Omicron era, the UK “SIREN” study of COVID infection in healthcare workers estimated that prior infection afforded 85% protection against a second COVID infection over 6 months. The reinfection risk estimated in the current study suggests this protection has fallen to 19% (95%CI: 0-27%) against an Omicron infection.
Prof Neil Ferguson from Imperial College London said: “This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination. This level of immune evasion means that Omicron poses a major, imminent threat to public health.”
