In a more concerning development, the efficacy of the mRNA Pfizer’s booster shot against symptomatic COVID-19 infection from the Omicron variant waned in just 10 weeks after the third shot, a new study has found this week. As the highly complex strain with more than 65 mutations and 32 mutations on spike protein has been spreading like wildfire, pushing cases of coronavirus to more than 100,000 for the first time since the pandemic hit in the UK, scientists and health experts have been weighing into the protection the vaccines provided against this hyper transmissible variant.

Unlike COVID-19 caused by other variants, Omicron has been showing unique symptoms among the patients along with the usual “high temperature, a new, continuous cough, or a loss or change to a sense of smell or taste” noticed in the case of Delta. Those who contracted Omicron also noted several other symptoms which aren’t usually associated with coronavirus, such as nausea and a loss of appetite.

Immunity offered by boosters ‘wanes more quickly’

But more worryingly, Britain’s Health Security Agency outlined the surveillance analyses related to risk assessments of B.1.1.529. It stressed that immunity offered by vaccines wanes more quickly with omicron than was previously seen in any other variant including SARS-CoV-2. “The protection conferred by booster vaccines against the omicron variant begins to wane within 10 weeks,” according to the technical briefing released by the UK Health Security Agency (UKHSA). British agency’s analysis was based on research of 147,597 Delta and 68,489 Omicron cases. Researchers shockingly found that Oxford/AstraZeneca, Pfizer/BioNTech, and Moderna COVID-19 vaccines are less effective against Omicron than Delta.

“There is evidence of waning of protection against symptomatic disease with increasing time after dose 2, and by 10 weeks after the booster dose, with a 15 to 25% reduction in vaccine effectiveness after 10 weeks,” the UKHSA said.

“This waning is faster for Omicron than for Delta infections. There are insufficient severe cases of Omicron as yet to analyze vaccine effectiveness against hospitalisation.” 

For those who received 2 shots of the Oxford/AstraZeneca vaccine, the third booster shot of Pfizer/BioNTech or Moderna will only be 60% effective at preventing symptomatic COVID-19 infection 2 to 4 weeks after the third booster dose. But this protection fades to just 35% to 45%  by 10 weeks. And those who received two initial doses of Pfizer/BioNTech, protection against Omicron falls from 70% at 2 to 4 weeks to 45% at 10 weeks after they take a Pfizer booster shot. The protection however falls to 70% to 75% by the 9th week after a Moderna booster shot. 

Some Omicron cases ‘third’ episode of reinfection

The UKHSA report also estimates that those infected with the B.1.1.529 variant may be 50% less likely to be admitted to the hospital, while a separate study published by Imperial College London found the risk was 15 to 20% lower compared to Delta. The vulnerable population or those with comorbidity may however face more serious COVID-19 and therefore health safety precautions are recommended.

The reinfection rate has increased sharply and disproportionately with Omicron, as per the UK agency. There are 69 identified cases with Omicron which are a “third” episode of infection, at least 290 cases of Omicron infection were recovered COVID-19 cases between a 60 to an 89-day interval of the recovery period. 

Britain’s Health Security Agency categorically stresses that to avoid the similar levels of hospital admission witnessed during the Delta wave, the Omicron B.1.1.529 strain will have to be 90% less severe than all strains previously detected. But the rate of spread of the new variant is dramatically worrying and risks overwhelming the hospitals, the UK government’s Scientific Advisory Group for Emergencies stated in the study.

“What we have got now is a really fine balance between something that looks like a lower risk of hospitalization – which is great news – but equally a highly transmissible variant and one that we know evades some of our immune defenses, so it is a very balanced position,” Jenny Harris, chief executive of UKHSA, told the Today programme, BBC Radio 4.

Just yesterday, the UK has recorded 119,789 new cases of COVID-19 shattering all records of the previous several months. UK’s Office for National Statistics estimates that 1.4 million people have contracted the COVID-19 this week. This is the highest yet comparable figure that was recorded in autumn 2020 during initial pandemic waves. “Omicron has continued to increase sharply as a proportion of cases in England, it is predominant in all regions of England,” the UK agency stressed. “The increase is also visible in wastewater, particularly in London and the South East,” it added. While Omicron has been behind the large community transmission, relative to Delta, it is currently more concentrated in young adult age groups between 20 to 29, the UKHSA warned. London, thus far as per the data until Dec. 20 has seen 40% hospitalizations from the Omicron variant. 

Of those hospitalized in London, 17 (12.9%) had received a booster dose, 74 (56.1%) a second dose, and 27 (20.5%) were not vaccinated (less than 10 were unlinked or had one dose). At least 14 people died within 28 days of an Omicron diagnosis, age range 52 to 96 years. The risk of hospital admission for a person detected as a case of Omicron appears reduced compared to a case of Delta. But this analysis is preliminary because of the small numbers of Omicron cases currently in hospital, and the limited spread of Omicron worldwide as the variant is in the initial stages of transmission and has not reached older age groups as yet, UKHSA noted.