Boosters Holding Back Worst of Omicron

Summary 

• European countries imposed new restrictions over the festive period following a sharp rise in cases. As a result, Germany now has the highest Stringency Index score out of the 50 countries we track. 
• Israeli data shows the importance of Covid boosters. It significantly reduces the chance of vaccinated individuals developing severe disease. It does not, however, prevent mild Omicron symptoms as well as it did for Delta. 
• High immunity in the UK has prevented hospitalisations from rising at the same pace as in the US and European countries. 

An Overview of Developments Over the Last Two Weeks 

A lot has happened over the festive period on the Covid-19 front. Officially, 0.3% of the world’s population contracted Covid-19 between 24 December 2021 and 6 January 2022. In Denmark, 4.3% of the population tested positive, with France (3.5%), Greece (3.5%) and the UK (3.3%) not far behind. As a result, several countries reintroduced restrictions, especially in Europe, where Spain registered a 12pp rise in its Stringency Index score – the biggest globally. Moreover, with a score of 84.3, Germany now has the highest Stringency Index score out of the 50 countries we track (Chart 1).

Promisingly, the UK Health Security Agency (UKHSA) reported a vaccine effectiveness against hospitalisation of 88% for Omicron after three doses. And so, booster programmes have been in full flow (Chart 2). In Asia, South Korea boosted 11% of its population over the last two weeks. And many EU countries find themselves in the top half of our list. Meanwhile, the US places just 46^th, having only boosted 2% of its population in the last fourteen days.  

Israeli Data Highlighting Importance of Boosters 

The importance of the booster is perhaps best visualised using hospitalisation data published by the Israeli Health Ministry. Data is broken down by symptom severity and vaccination status. Three trends emerge. First, the vaccine provided significant protection across the full range of symptoms during the Delta wave. That is, the unvaccinated were far more likely to enter hospital and report either mild, medium, or severe symptoms (Charts 3-5).  

Second, the effectiveness of the first two doses waned dramatically after seven to eight months. In August, the share of vaccinated individuals in hospital reporting mild, medium, or severe symptoms became greater than the unvaccinated share. Third, during the Omicron wave, the booster continues to protect the vaccinated against severe disease, but is no longer as effective at preventing mild and medium symptoms (Chart 3 and 4 vs Chart 5). Now, around 60% of individuals in hospital reporting mild symptoms are vaccinated. 

As a result, it is likely that rising hospitalisation numbers will mask the severity of Omicron. The proportion of mild and medium hospitalisations will likely increase, as they have done in Israel (Chart 6), but severe cases and deaths should remain low if booster programmes are successful. This means that slow booster rollouts in Asian countries could make them susceptible to Omicron spreading from Europe. India is yet to start boosting (Table 1) and weekly infections are up 309% from 66,000 to 270,000 cases.  

Hospitalisations, and the UK 

Hospitalisations are beginning to pick up in some of the countries that report the data (Chart 7). Italy and Spain have recorded 203% and 184% WoW increases in weekly hospitalisations, respectively. The US has one of the highest number of hospitalisations per million, and is not far off last January’s peak – the figure has also risen 17% WoW.  

Meanwhile, the UK has not seen hospitalisations rise anywhere near as substantially as Italy, Spain or the US (Chart 8). This is despite recording many more cases over the last month, and nearly double those registered in the US on a per head basis (Chart 9). This must partly be related to its booster rollout, where over 50% of the UK’s total population has now been given a third dose (Table 1).  

Bottom Line 

The Omicron wave will inevitably cause hospitalisations to rise in countries where it has taken grip. But, the booster does appear to be limiting the worst of the disease. That, alongside evidence that the virus itself is less severe, should mean that hospitalisations will not translate into significantly higher deaths. That being said, countries not as far along in their booster rollouts will give the virus the opportunity to cause severe disease in the previously double vaccinated population. And so, given the infectiousness of the virus, we could yet see large Omicron-related disruptions in less prepared countries, such as India.