Research shows delta variant can be spread by vaccinated, unvaccinated people


State health officials warned July 30 that new research indicates the COVID-19 delta variant spreads as easily as chickenpox and measles and that it can be spread similarly by vaccinated and unvaccinated people.

Since May, the delta variant has become the predominant strain in Indiana, accounting for more than 90 percent of samples sequenced in July. Indiana State Health Commissioner Dr. Kristina Box said the new data shows infected people, regardless of vaccination status, can spread the delta variant to as many, on average, as 8 other people, making it approximately as contagious as chickenpox, which she said is of significant concern because more than half of Indiana’s population remains unvaccinated and more vulnerable to the disease.

On July 27, the Centers for Disease Control and Prevention issued new guidance, calling for all people 2 and older to wear masks in areas of substantial or high transmission of COVID-19, which includes all of central Indiana, regardless of vaccination status. The change from its May guidance, which said vaccinated individuals could go without a mask in most settings, was inspired by new research the CDC was conducting but had yet to publish at the time. The CDC in collaboration with the Commonwealth of Massachusetts Dept. of Public Health has been conducting an outbreak investigation of multiple large public events in Barnstable County, Mass., and on July 30 some of the investigation’s data was published in the CDC’s Morbidity and Mortality Weekly Report.

CDC Director Dr. Rochelle P. Walensky stated the data demonstrated a delta infection resulted in “similarly high SARS-CoV-2 viral loads in vaccinated and unvaccinated people.” The viral loads of people infected with the delta variant are significantly higher than in the viral loads of people infected with previously dominant variants of the virus, which health officials say has caused a recent surge in cases in Indiana and across the country, though case numbers remain below record winter highs. The data led the CDC to issue its new guidance, Walensky stated.

“The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones,” Walensky stated July 30.

Because of the new research, the CDC recommends all close contacts, regardless of vaccination status or symptoms, get tested for COVID-19 three to five days after their exposure. Box said the definition of a close contact has not changed with the CDC’s new guidance.

“COVID-19 is a communicable disease that must be reported to the state and local health departments and that isolation is required when an individual tests positive,” Box said.

All K-12 institutions are required to report all positive cases to the state health department and its local health department. The ISDH recommended all school districts follow CDC guidelines that recommend all students, teachers and staff wear masks in school. The department stopped short of mandating masks because of a “philosophical” belief that local officials, who were elected by their constituents, are the best people to determine whether a district should require masks, Box said.

As of July 30, the state had not discussed imposing capacity limits on businesses or gathering restrictions for its residents, Box said. She said a vaccine mandate has not been considered, either.

State health officials continue to push vaccines as the best line of defense against the virus, citing ISDH data showing unvaccinated residents account for 98 percent of the state’s new COVID-19 cases and 96 percent of its COVID-19 hospitalizations, though data shows breakthrough cases are more likely with the delta variant; however, breakthrough cases are often present milder symptoms.

In recent weeks, an increased demand for COVID-19 testing has coincided with the reported increase in cases and numerous outbreaks in long-term care facilities. The state’s seven-day average positivity rate, which measures the number of tests that result in a positive COVID-19 diagnosis, has increased, rising from 2.1 percent on June 23 to 6.8 percent as of July 23, the highest it has been since January. COVID-19 hospitalizations and daily admissions are also on the rise, but remain below peak levels. Deaths remain at a record low, but Box warned deaths tend to lag behind an increase in cases.


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