The highly transmissible Delta variant of COVID-19 does not appear to cause more severe disease among fully vaccinated or unvaccinated hospitalized patients, compared to earlier forms of the virus, according to preliminary data from the Centers for Disease Control (CDC).
The CDC study, released on Oct. 22, analyzed some 7,600 patients hospitalized with COVID-19, the disease caused by the CCP (Chinese Communist Party) virus, in the months of July and August, when the Delta variant became predominant in the United States. Researchers found that compared to earlier months, there was no significant change in hospitalized COVID-19 patients’ outcomes.
Specifically, although adult hospitalizations surged during the Delta wave, compared to the six months prior, the proportion of patients with COVID-19 who were admitted to an ICU, received invasive mechanical ventilation (IMV), or died during their hospitalization did not significantly change during this period, the data suggests.
The research however shows that adults aged 18 to 49, many of whom were unvaccinated, accounted for a larger proportion of hospitalized patients compared with the pre-Delta period—35.8 percent of hospitalizations compared to 24.7 percent from the previous six months.
Roughly 71 percent of COVID-19–associated hospitalizations during the Delta wave were in unvaccinated adults, the researchers said, adding that the lower vaccination coverage in the 18 to 49 demographic likely contributed to the increase in hospitalized patients during the Delta period.
The Delta variant of the CCP virus grew in prevalence in the country from 1.8 percent on May 1 to over 85 percent on July 10. It is now the dominant strain around the globe and has been reported in at least 187 out of 194 World Health Organization member countries, the organization earlier this month.
“Although this variant is more transmissible, this study did not find significantly higher proportions of hospitalizations with ICU admission, receipt of IMV, or in-hospital death in nonpregnant hospitalized adults,” the CDC study states.
They acknowledged a number of limitations, including that during spikes in COVID-19 cases during the Delta wave, the clinical thresholds for hospitalization and ICU admission might have shifted and could therefore have potentially obscured trends in increased severity.
The researchers also noted that some patients could also have been hospitalized but not tested for the virus, and the data could potentially change including cases from the summer months who do not yet have a discharge disposition.
A separate preprint study published on medRxiv on Oct. 6 suggests that children also do not get any sicker from the Delta variant than they did from earlier strains.
Researchers compared two groups of school-age children with COVID-19: 694 infected with the Alpha variant between late December 2020 and early May 2021, and 706 infected with Delta between late May and early July.
In both groups, very few children needed to be hospitalized and long periods of illness were uncommon. In both groups, half of the children were sick for no more than five days.
“Our data suggest that clinical characteristics of COVID-19 due to the Delta variant in children are broadly similar to COVID-19 due to other variants,” the researchers concluded, echoing remarks from CDC Director Dr. Rochelle Walensky in September that although more children are getting infected with the virus, studies show that there has not been an increased disease severity in children.
“More children have COVID-19 because there is more disease in the community,” Walensky said of the Delta-driven wave in a statement.