Latest COVID-19 modeling projects continued decline in hospitalizations if no new variant appears in Colorado

Bivalent boosters could help blunt potential surge in cases and hospitalizations, modelers say
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Posted at 12:50 PM, Oct 11, 2022
and last updated 2022-10-11 14:55:35-04

DENVER – COVID-19 hospitalizations are projected to continue declining through the end of 2022 if the BA.5 sublineage of the omicron variant remains the dominant variant of concern in Colorado for the remainder of the year, but things could change should a more virulent and infectious variant take hold, the latest report from the state’s COVID-19 modeling team shows.

Though statewide hospitalizations for COVID-19 have increased over the past two weeks in Colorado, other data trends show a mixed picture of the trajectory of the virus: SARS-CoV-2 wastewater concentrations indicate a slow decline in infections statewide but increases in some regions, for example, and the state’s positivity rate has plateaued above 5%, modelers from the Colorado School of Public Health wrote in their latest report, dated Oct. 6.

“It is unclear if the recent rise in hospitalized COVID-19 patients is due to chance or a shift in disease patterns,” the modelers noted. “Notably, hospital admissions continue to decline nationally and in Colorado.”

Currently, the modeling team estimates 1 in every 188 Coloradans are currently infected with the virus – up from their estimate of 1 in every 162 infected from late August – a decline from summer highs but similar to infection levels from February, after the original omicron wave.

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Coloradans are estimated to have high levels of immunity both from infection and severe disease following the summer BA.5 wave, with about 90% of the state population having immunity against severe disease and 75% immunity against infection, according to the estimates from the modeling team.

Statewide COVID-19 data showed 90% of infections statewide were from the BA.5 variant, with BA.4.6 accounting for a little over 7% of all infections in the state as of mid-September, but two new omicron subvariants have since emerged in Europe and West Africa which could change the trajectory of SARS-CoV-2 in Colorado.

Though not highly prevalent in the U.S. right now, “early reports suggest that BF.7 (also called BA.2.75.2) and BQ.1 may have greater immune escape over BA.1, BA.2, BA.4 and BA.5 variants,” the modelers wrote.

The BF.7 sublineage, which has been reported in Belgium, Denmark, Germany and France, makes up about 3.4% of all current U.S. cases, according to the latest U.S. Centers for Disease Control and Prevention (CDC) data and has a growth advantage over BA.5 of about 6% per day. A study estimated BF.7 has six times the ability to neutralize antibodies from vaccination or prior infection compared to BA.5, making it the most immune evasive variant to date, according to the COVID-19 modeling team.

BQ.1, a cousin of the highly transmissible BA.5 variant, is circulating in England, France, Nigeria and the U.S., they said, but there’s not enough data yet to say how much growth advantage it may have over BA.5.

“BA.5 and BA.4.6 are currently the dominant VOC [Variants of Concern] in the U.S., but there are predictions that the rising subvariants BF.7 and BQ.1 may be more prevalent in the U.S. by the end of November,” they wrote.

That’s why uptake of the COVID-19 vaccine bivalent boosters, which target the BA.4/5 sublineages of the omicron variant are so important at the moment, they said.

To date, approximately 2% of Coloradans have received a bivalent booster – a slower uptake when compared to the first boosters of the original COVID-19 vaccine. The decline in booster uptake is happening across all age groups, statewide data show.

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Should a new, more virulent and/or more infectious variant arrive in Colorado, the COVID-19 modeling team projects hospitalizations would increase to between 300 if the variant has the same level of virulence as BA.5, and to 1,200 if the newer variant is as virulent as the delta variant from last fall.

The modeling team, however, projects between a 3.9% and 4.2% reduction in infections if Coloradans boosted with the latest COVID-19 vaccines encounter both of these scenarios so long as current booster uptake remains the same through the end of 2022.

If the current bivalent booster uptake continues through the fall, Coloradans should expect about a 3.9% reduction in hospitalizations should a more virulent and/or more infectious variant arrive in Colorado, the modelers projected. “The future benefit of bivalent boosters depends on booster uptake and the characteristics of the next variant,” modelers wrote in closing remarks.

The COVID-19 bivalent booster targeting the BA.4/5 sublineage of the omicron variant is available for people 12 and older (Pfizer) and for people 18 and older (Moderna) so long as two months have passed since your last COVID-19 shot and three months have passed since your last COVID-19 infection.