The ominous warning comes from experts at Imperial College London. 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 29 and December 11 2021. Experts found "no evidence" of Omicron having lower severity than Delta, but it did find a worrying reinfection ability.

       To assess the impact of Omicron on reinfection rates the researchers used genotype data.

       They found the new variant's rate of infection was more than five-fold more than Delta.

       But the vaccine protection adds even more gloomy data.

       A previous study of healthcare workers estimated that prior infection afforded 85 percent protection against a second COVID infection over six months.

       But the new study places it as low as 19 percent.

       They also found a "significantly increased risk" of developing a symptomatic Omicron case compared to Delta for those who were two or more weeks past their second vaccine dose.

       It translated into a vaccine effectiveness rate of between 0 percent and 20 percent after two doses.

       This is compared to a 55 percent to 80 percent prediction after a booster dose.

       Similar estimates were obtained using genotype data, albeit with greater uncertainty.

       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.”

       Prof Azra Ghani from Imperial College London said: “Quantifying reinfection risk and vaccine effectiveness against Omicron is essential for modelling the likely future trajectory of the Omicron wave and the potential impact of vaccination and other public health interventions.”