Omicron in the undervaccinated world

Even with lower severity, Omicron's contagiousness may still wreak havoc on the developing world

Omicron’s contagiousness may be particularly well-suited to wreak havoc on the developing world.  

Why worry about Omicron?

Recall India earlier this year in May when Delta was spreading. The chart below shows how our best available estimates of cumulative excess deaths evolved during this period across World Bank income groups (these are the mid-point estimates of the excess death model by The Economist). Note the steep change of slope in the South Asia curve around May. That was India.

Omicron has shown itself to be more infectious and more immune evasive than Delta, which took India by surprise. A key worry is that the hyper-contagious nature of Omicron will cause a repeat of what we saw in India. There are two structural reasons for that. 

  • Poverty, informality and density. Conditions in poorer developing countries tend to facilitate not reduce spread. This is particularly true in the dense urban areas of the developing world, where poverty, informality and the more limited scope for lockdowns and other NPIs will contribute to the spread. So if Omicron has a short half-life in rich countries, it’s likely to be even shorter in the dense urban settings of many developing countries.
  • Less-resourced health systems. Health systems around the world have shown over and over again to have difficulties dealing with rapid surges (which is why richer countries have imposed lockdowns). Even if Omicron is less severe, its hyper-contagious nature coupled with the higher chance of reinfection may still create a considerable need for oxygen, ventilators and other medical supplies as well as of course medical staff, which will pose again difficulties for the developing world. 

The state of global vaccination progress

Preliminary reports suggest “Omicron is less severe than previous variants”. A recent (as yet not peer-reviewed) study from the University of Hong Kong found that Omicron replicates faster than the original SARS-CoV-2 virus and Delta variant in the human bronchus. At 24 hours after infection, Omicron replicated around 70 times higher than the Delta variant and the original SARS-CoV-2 virus. In contrast, the Omicron variant replicated less efficiently (more than 10 times lower) in the human lung tissue than the original SARS-CoV-2 virus, which may suggest lower severity of disease.

However, as Eric Topol notes in this interview on PBS, we have no conclusive evidence that the virus itself is more mild. Reduced severity so far appears to be thanks to prior immunity not the pathogenicity of the virus itself. We have no firm data yet on how the virus is affecting the unvaccinated or the previously uninfected. 

What is clear however is that any beneficial effect of prior immunity due to vaccination must be weighed against the fact that global vaccination progress remains highly incomplete and unequal.  

The above chart shows in the first bar the primary vaccine coverage ratio (exclusive of boosters), where 200 doses per 100 people represents full vaccination (200 because doses have been adjusted into 2-dose vaccine equivalents; read more on this adjustment here). The latest data point suggests we’re still a long way off.

The dot inside the first bar shows booster coverage globally, where boosters are any vaccine doses that have been administered beyond the primary vaccination protocol represented by the bar. Given that progress on primary vaccinations remains highly incomplete, it comes as no surprise that booster progress is even more limited.

We also see that coverage progress for both primary doses and boosters is highly unequal. The visualization shows four groups of countries according to the World Bank’s income classification: high-income (HIC), upper-middle-income (UMIC), lower-middle-income (LMIC) and low-income (LIC) countries, with the latter three representing the developing world. Coverage is systematically lower especially for the LMICs and LICs, which together represent 52% of the world’s total population.

Omicron's current and future impact

Vaccination and previous infection have the potential to reduce the severity of Omicron and the combination of both (hybrid immunity) may in principle be particularly effective. 


  • Preliminary evidence suggests that immunity levels need to be boosted to provide sufficient protection against severe disease. Aggarwal and others (2021) confirm a 16x drop in neutralization capacity towards Omicron of serum/plasma from both (twice) vaccinated and convalescent patients. But boosters increase the calculated or estimated vaccine efficacy.
  • Evidence from Israel dating back before Omicron also suggests that the powerful effect of hybrid immunity wanes over time, pointing to the need for updated vaccinations to raise immunity levels. Whether this conclusion also holds with respect to Omicron was not tested but one can only speculate it does even more so.

While the above suggests a need for additional vaccination to protect against Omicron, the question becomes how to meet that challenge. Even as of today, almost a year into the global vaccination campaign, the world continues to be poorly and unequally vaccinated. 

Moreover, even if severity can be successfully reduced, there is the worry that the scale of infection and re-infection will be such that still a large number will need to be hospitalized. This will pose a problem for the less-resourced health systems around the world that will hit capacity constraints first. 

The current Omicron episode once again demonstrates that until and unless we ramp up our capabilities to scale up, distribute and administer updated vaccines, we will remain vulnerable to potentially more dangerous variants. 

At the heart of NATO’s founding treaty is the principle of “collective defense”: an attack against any ally is an attack against all allies. To get over the battle of this pandemic, we need to more fully embrace such principle at the global scale and realize that we’re all allies. Anything less is short-sighted and ineffective. 

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The world remains underprepared against the downside contingency of a highly contagious and more lethal variant. If it materializes, what will we wish then we had done differently today?

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