A medic tends to COVID-19 patients at the ICU of Pirogov Hospital in Sofia, Bulgaria, October 15, 2021. Photo: Reuters/Stoyan Nenov
- The European Centre for Disease Control and Prevention has assessed the risk of a full-blown outbreak of the omicron variant to be ‘very high’.
- The body used the prevailing rate of increase in the number omicron cases to project that it could become the dominant strain in all EU countries by February 2022.
- Like some studies thus far, the body also pitched for EU countries to roll out booster doses while also asking for more effectiveness and in vitro studies.
New Delhi: In its latest assessment, the European Centre for Disease Prevention and Control (ECDC) has warned that the omicron variant of the novel coronavirus over other existing variants of concern and could potentially present a whole new set of challenges in the fight against the COVID-19 pandemic, and determined the probability of further spread of the omicron variant in the European Union to be ‘very high’.
The assessment, released on December 15, said the omicron variant got its edge from two factors: high ‘growth rate’ and the ability to evade neutralising antibodies generated by a full vaccine regimen.
The ‘growth rate’ is the day to day rate of increase in the number of people infected by the variant. A rate of lower than 1% would mean the outbreak is not spreading exponentially. According to the ECDC, as of December 10, the growth rate in the UK was 35% per day, which implied that the number of people infected by the omicron variant would overtake the number infected by the delta by mid-December.
This isn’t the first warning the world has received on the omicron variant’s growth rate. In the WHO’s December 14 virtual presser, Abdi Mahamud, a member of the WHO’s COVID-19 Incident Management Support Team, had said that this parameter usually doesn’t get much attention but is actually crucial. “The growth rate of omicron is what’s making us really worried about the impact it will have on health systems,” he had said.
As virologist Gagandeep Kang and other experts have noted, a sudden increase in the demand for healthcare can overwhelm a healthcare system that is well-equipped but still not sufficiently prepared.
The ECDC stated that if the EU’s member nations didn’t start preparing right away, the omicron variant could overtake the delta variant in terms of the number of active infections by February 2022 – although in some countries it could become the dominant strain by late December itself.
Another, and better-known, indicator of a strain’s path to dominance is the doubling time: the amount of time in which the number of cases doubles. The ECDC assessment said this seems to be in the order of one or two days based on preliminary data from South Africa and two or three days based on data from the UK and Denmark.
At its peak, the number of new infections by the delta variant doubled every 4.5 days in the UK.
While the international scientific community is near-unanimous that the omicron variant is much more transmissible than the other variants of concern, there is much we need to find out about the severity of the infection it causes. The ECDC said in its report that there is little data yet on this point, even if cases of severe COVID-19 due to an infection of the omicron variant have been “rare” in the EU.
In fact, its report said that no one with an omicron infection has been admitted to the ICU or has died. The UK – which isn’t part of the EU – has reported one death among omicron cases thus far.
This said, South Africa’s experience thus far has been for the number people hospitalised with COVID-19 to climb in tandem with the number of people infected by the omicron variant. According to the ECDC, 153 people were hospitalised with COVID-19 in South Africa in the second week of November versus 2,201 people three weeks later.
On the other hand, while the number of cases increased by a greater amount than it had in previous waves in similar periods, the hike in the number of hospitalisations was still comparable to those in previous waves. Experts have interpreted this as an indication that infections of the omicron variant may not be more severe than those caused by other variants.
The ECDC, the WHO and other major health agencies have all introduced a caveat at this point, however: the data we have is preliminary and could change adversely in the coming weeks, which in turn means we can’t be complacent without also courting more risk.
Beyond the variant’s impact on people, the other big question – perhaps bigger – is its impact on vaccines. The ECDC assessment alludes to in vitro studies (conducted in the laboratory) reporting a drop in antibody levels generated by a full primary vaccination course, which is two doses in the case of most existing vaccines. But the complete picture of the variant’s impact on vaccine-induced antibodies – including whether vaccines can continue to prevent severe disease and hospitalisation – remains unclear.
According to the assessment, “vaccine-induced cell-mediated immunity” – a.k.a. long-term immunity – that reacts to parts of the virus beyond its receptor-binding domain “may also play an important role in protection from severe disease following infection by omicron”. The receptor-binding domain is the part of the spike protein the virus uses to bind with receptors in the human body.
Nonetheless, the drop in the volume of neutralising antibodies suggests that vaccines may not be able to help prevent infections, onward transmission and mild disease due to the omicron variant. And the ECDC assessment – like a recent small study out of the UK – used this point to pitch for booster doses.
Kang recently articulated to The Wire Science the importance of using mRNA vaccines specifically as booster doses: “So far it looks like having an mRNA vaccine in the mix is giving the best result”.
But after pitching for booster doses, the ECDC assessment also issued a call for more studies:
“More clinical studies on the effectiveness of boosters against the omicron are urgently required (to date only one study is available), as well as more studies and real-life data on the impact of the omicron on waning immunity following vaccination or natural infection.”
In India, there has neither been a study on the need for booster doses nor on the variant’s impact on vaccine effectiveness. One reason is that the case load of infections due to the omicron variant is still low in the country. At the same time, in vitro studies are only just getting underway.
Overall, the ECDC’s position appears to be that vaccination coverage must increase, non-pharmaceutical interventions like masking and physical distancing must be followed, vaccination coverage must increase, we must consider booster doses – and we must also conduct more studies to inform these decisions.
In addition, the assessment also advises governments to develop flexible testing strategies that can adapt quickly to changing facts, even as hospitals prepare for possible surges in healthcare demand.