A study by the U.S. Center for Disease Control and Prevention (CDC) found that the Delta variant of Covid causes a similar viral load in vaccinated and non-vaccinated individuals.

The study is based on 469 Covid cases found among Massachusetts residents who traveled to Barnstable County for a summer vacation between July 3 and 17, 2021. Of these, 346 (74%) were fully vaccinated. Delta variants were found in 90% of the samples taken from 133 patients.

Cycle threshold (CT) values were similar in samples of patients who were vaccinated and those who were not. The CT value is a measure of how quickly the SARSCOV-2 virus can be detected in a sample during RTPCR testing. It calculates the frequency at which the viral RNA in the sample must be amplified in order to reach a detectable level. The similar CT value in both groups indicates that the viral load is similar.

People with high viral loads are also more likely to spread the disease to others. Covid is different from other variants in people who have been vaccinated against the Delta virus. In the light of the study, CDC Director Rochelle Valensky pointed out that it can spread.

The findings of this study prompted the CDC to revise its guidelines on mask use. The CDC initially suggested that vaccinated people should not wear masks in public places, and later recommended that everyone wear the mask in public places such as schools and offices.