US IHME Covid Projections Now Include Immunity Waning and the Omicron Variant
The IHME (Institute for Health Metrics and Evaluation) at the University of Washington has moved to every two week updates, but had paused a month until more details of the Covid-19 Omicron Variant infections were known. They now cover Omicron with both a Reference Projection and a High Severity Projection. Some experts think it may take a month to gather hospitalization and death data with holiday disruptions.
Omicron is now the dominant variants in the US, and the IHME US Policy Briefing now projects over 60% of Americans will be infected by it over the next two months. Over 90% of the infections will be asymptomatic. Their model uses an Infection Hospitalization rate of 0.90%-0.96%, or less than 1% of the Delta variant rate. Their projected Covid deaths in February are greater than 2,000 a day. In their High Severity Projection, that rises to 2,900 deaths a day. Those are to be compared to the present Covid death rate of 1,300 a day. While the projected death rate per infection is lower, the rate of infectability is higher with Omicron. In the High Severity projection, Hospitalization is taken as 2.3 times the Reference Projection, and Fatality is taken as 4.6 times the Reference Projection. However, in the High Severity projection explanation with the graphs below, those factors are taken as 2 times for hospitalizations and 3 times for deaths.
Their Reference scenario of Booster shots is that 80% of the fully vaccinated get them. Currently, only about a third have gotten them. Projections with Boosters increased to 100% has little extra effect. Presently, only 61.7% of Americans are fully vaccinated with just two shots, and 71% has at least one dose. They project 72% fully vaccinated by April 1.
The preventative action that has the most effect, and which can be done immediately, is to extend masking to 80%. They also promote the use of KN95 or N95 masks, but this is not modeled. Currently, only 38% are masking, although California is over 50%. They do not recommend closing primary or secondary schools. The effectiveness of 80% masking is a very welcome Christmas present, since the growth in vaccinations and boosters has been so slow. The peak infection rate in the Reference and other projections is 870/100,000 per day, but with 80% Masking, this is cut in half to 450/100,000 per day. Current US mask use is only at 38%. They also state that social distancing is more effective than masking, but I think that this means shutting things down. Cloth masks they say for the general population reduces transmissibility by 1/3, medical masks by 0.55, and other masks by 0.67, without further definintions.
They estimate that 38% of the US has been infected at least once, and the detection rate is only at 34%.
A short table for the US vaccinations that IHME uses in Preventing Infections and Severe Disease follows.
| Vaccine | Prevent Infections | Prevent Severe Disease |
| Pfizer | 44% | 72% |
| Moderna | 48% | 73% |
| J and J | 33% | 57% |
Results from IHME Covid-19 Projection Graphs for the United States
The various projection conditions are listed below:
The graphs of Projections for Current Estimated Daily Infections for the United States is below.
The Estimated Daily infections for the US for today from above is rounded as 1.15 million, whereas the reported 7 day average today, December 24, is 176,097, or only 15%.
The count for Estimated Daily Infections for the US on January 27 near its peak below is 2.81 million on the Current Projection. The 80% mask us would reduce this to 1.40 million, or half, which seems to be a standard ratio for this case. Clearly, hospitalization and deaths which follow would also be reduced by half. Reducing vaccine hesitancy to zero or increasing third doses to 100% from 80% has almost no effect.
The projections for Daily Deaths for the US is below.
Daily US deaths at its peak around February 13, 2022 is 2,300 in the Current Projection, but can be reduced to 1,140, or again, about half, by going to 80% masking.
For California, below, Daily Deaths at its March 14 peak can be reduced from 189 to 104 by going to mask use of 80%. Current mask use in California is 53%, although the Governor has now instituted a mandate for indoor mask use. Again, vaccine increases do not have such a major effect.
