The previous post on evolution brings us to the Delta and now Omicron variants of SARS-CoV-2, the virus that causes COVID-19. A strain that is more contagious (meaning it is better at spreading from one person to others) will quickly come to dominate the population of virus strains. Delta was more contagious than the original strain but at least a little less deadly. Omicron is now more contagious than the original strain, but a lot less deadly, like at least 4 times and maybe as much as 40 times less likely to cause death! That means it is far less deadly than the flu and about as deadly as the common cold. I’ll bet you didn’t hear that from the media or Anthony Fauci.
Here’s how I arrived at that 4- to 40-fold less deadly number. First, by deadly I mean the infection fatality rate (IFR), which is defined as deaths/infections or the likelihood of dying once you are infected.
Ferguson et al. (Reference 1) gives data from the British health service on the PCR tests of every person tested for COVID from Nov. 29 to Dec. 11, 2021 in the U.K. The PCR test shows not only whether they are infected but also whether they are infected with the Omicron strain (designated S-) or another strain, probably Delta. The key data for me is this:
If you are infected with Omicron, you are 4.2 times less likely to be hospitalized than if you are infected with another strain. That is actually a lowest limit on the magnitude of the difference because people infected with Omicron have milder disease and are more likely to be asymptomatic, so they are less likely to go in for a PCR test. If you are entirely asymptomatic you will not go in, and if your symptoms are mild you are less likely to bother to get tested.
Another data point caught my eye in this paper, which suggests to me that the main evolutionary advantage of Omicron over Delta is that it is better at reinfecting people who were previously infected, meaning it is better at evading immunity from prior infection (which would make sense because prior infection was with a different strain and you immunity would be best against that same strain).
The reinfections are only 10% of the omicron cases, so 90% of the persons were not previously infected with COVID. And still only 0.15% of them were hospitalized. So the decreased hospitalization risk of omicron is not due to infecting only previously infected people who have partial immunity; it is an inherent decreased lethality.
The second paper I turned to in order to calculate the lethality of omicron compared to previous strains is Maslo et al., (reference 2), published in JAMA, the Journal of the American Medical Association, with data from South Africa.
Look at the bottom line of deaths. The relative death risk, of hospitalized patients, is 2.7% in the omicron wave and 25.5% last year in the earlier wave, 9.4-fold lower for omicron. Since 66% of patients in the omicron wave were unvaccinated, even if all the deaths occurred in unvaccinated persons, the risk of death in the omicron wave would still be 6-fold lower than in previous waves. And that can be viewed as a lowest estimate of the difference, because not all of the patients in Nov.-Dec. 2021 had omicron. If some had delta or a previous strain, they would have a higher risk of death and might account for some or even all of the COVID deaths in the time period of the omicron wave.
Also, note that all the other risks were significantly lower in the omicron wave—more than 4-fold less risk of needing oxygen therapy, half the risk of intensive care admission, and less than half of the time in the hospital.
The Ferguson paper did not report deaths, perhaps because there were no deaths with omicron, but the relative infection fatality rate would be equal to relative risk of hospitalization times the risk once you are hospitalized of dying from COVID. Ferguson’s data shows 4.2-fold lower risk of hospitalization and Maslo’s data shows over 9-fold lower risk of dying once you are hospitalized. Relative Infection Fatality Rate of omicron versus delta is then 4.2 x 9 = 38-fold lower!
Another way to look at this is the ratio of deaths to cases over time as the omicron variant has become common.
In the U.K. only about 7% of COVID cases were omicron in Nov. 29 to Dec. 11, 2021. In October no cases were Omicron. By January 1 if 100% of cases were Omicron, then this ratio that omicron is 4.3-fold less deadly would be correct, but if only 10% of cases were Omicron, which is probably closer to reality, it would be more like 43-fold less deadly.
For South Africa, the numbers in their three most recent waves were as shown in Table 5 below. Each of these dates represents a peak of COVID cases and deaths corresponding to the beta (1/15/21), delta (7/15/21), and omicron (12/15/21) strains of the COVID virus (Reference 2).
South Africa is the best nation for this data because it is the one with the highest percentage of omicron cases. By Dec. 15, 2021 the majority of their cases were omicron (Reference 2). But not all were, so these ratios can still be viewed as low estimates of the ratio of lethality of omicron to earlier strains.
The lower lethality on Dec. 15 than the earlier dates could partially reflect higher vaccination. But according to reference 4, as of January 1, 2022, about 25% of South Africans were fully vaccinated, and fewer than a quarter of those or about 7% were vaccinated by July 15, 2022. So the vaccination does not have a huge effect on this data. Perhaps the ratio of 18 to 1 in lethality of omicron versus delta should be cut at most by 25% to about 14.
The original strain of COVID was only 1.7-fold more deadly (1.7-fold higher infection fatality rate) than ordinary influenza if you have not been vaccinated against either. So if omicron is even 4-fold less deadly than the original strains, it is less than half as deadly as influenza. More likely it is at least 10-fold less deadly and by one calculation above 38-fold less deadly. In any case, we have little if anything to fear from the omicron variant. It is less than half as deadly as ordinary flu and maybe no more deadly than the common cold.
In any rational world, the fact that omicron is far less deadly than the earlier strains of COVID and far less deadly than ordinary influenza would be greeted as great news and as a reason to declare that there is no reason not to go back to normal life. But that is not how our leaders have reacted to this. Instead, they have latched on to it as an excuse to reinstate restrictions. For some reason they seem to be desperate for an excuse to continue the lockdowns and the restrictions.
1. Ferguson, N. et al. 2021. Report 49: Growth, population distribution and immune escape of Omicron in England. Dec. 16, 2021. DOI: https://doi.org/10.25561/93038.
2. Maslo, C. et al. 2021. Characteristics and Outcomes of Hospitalized Patients in South Africa During the COVID-19 Omicron Wave Compared With Previous Waves. JAMA Dec. 30, 2021. https://doi.org/10.1001/jama.2021.24868
4. https://covidvax.live/location/zaf, accessed January 2, 2022.