In-Depth: Why the CDC says delta 'is likely' more severe

delta covid
Posted at 5:13 PM, Aug 06, 2021
and last updated 2021-08-06 21:31:01-04

SAN DIEGO (KGTV) -- Doctors and researchers aren’t yet ready to conclude the highly transmissible delta variant causes more severe illness than previous versions of the virus, but mounting evidence suggests it does.

The Centers for Disease Control and Prevention warned the delta variant is “likely more severe” in an internal document released last week. The document noted that vaccinated people have a 25 times lower risk of hospitalization than the unvaccinated.

The severity assessment was based on studies in Canada, Singapore and Scotland.

In each study, the researchers examined cases and hospitalizations, adjusting for factors like age, gender and underlying conditions. They found people infected with delta had a much higher risk of hospitalization than those infected with the original form of the virus.

The Scottish study examined 19,543 cases and 377 hospitalizations, of which 134 hospitalizations were from the delta variant. The risk of hospitalization from delta was 1.85 times higher.

In the Canadian study, which was updated Aug. 4 with new data, the risk of hospitalization from delta was 2.08 times higher. The risk of death was 2.32 times higher.

Experts say the studies examined limited populations and have not yet undergone peer review. The delta variant's extraordinary infectiousness could also drive up the number of severe cases.

However, the studies broadly align with what Dr. Christian Ramers says he’s seeing at Family Health Centers of San Diego.

“Compared to last year, I think we're seeing sicker people,” he said.

Early research suggests the delta variant strikes faster, making people sick within three to four days after infection compared to five to seven days for the older version. It also multiples 1000 times more within the body.

But statewide, California’s death rate from COVID has remained low even as cases have spiked. The death rate has stayed about the same as the level in June, when the state lifted business restrictions.

That’s partly because deaths are a lagging indicator, Ramers said. It typically takes about three weeks after infection for a person to die from COVID.

But there could be other confounding factors at play.

“The pool of people that are getting COVID is, by and large, unvaccinated people,” he said. “That tends to be more of the 20- to 30-year-old folks.”

Hospitals are reporting a younger patient population, which might skew the death rate, he said. Younger patients tend to be more resilient to disease in general.

At the same time, more than 70 percent of Californians over age 50 are now fully vaccinated.

“It may be that we have a very well protected vulnerable population, so deaths won't go up that much. And I know we now have treatments that are better than they were before,” he said.

Treatments like monoclonal antibodies are more readily available for high-risk patients soon after infection, he said.

The infusions can even be given to people who have been vaccinated, adding an extra layer of protection and an extra variable for scientists trying to calculate delta’s severity.