![]() ![]() ![]() "High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus," she said. Walensky disregarded that caveat in the press release the CDC issued when it published the Provincetown study, saying the researchers found "Delta infection resulted in similarly high SARS-CoV-2 viral loads in vaccinated and unvaccinated people." Still, she did not claim that vaccinated carriers were as infectious as unvaccinated carriers. The researchers reported that cycle threshold (Ct) values, which indicate the extent to which the nucleic acid targeted by a RT-PCR virus test has to be amplified before the fluorescent signal rises above the background level, "were similar among specimens from patients who were fully vaccinated and those who were not." But they cautioned that "Ct values obtained with SARS-CoV-2 qualitative RT-PCR diagnostic tests might provide a crude correlation to the amount of virus present in a sample and can also be affected by factors other than viral load." While the similar Ct values "might mean that the viral load of vaccinated and unvaccinated persons infected with SARS-CoV-2 is also similar," they said, "microbiological studies are required to confirm these findings." ![]() Three days later, we finally got a look at some of those data, reported in an MMWR article about a July outbreak in Provincetown, Massachusetts, that primarily involved the delta variant. "Emerging evidence suggests that fully vaccinated persons who do become infected with the Delta variant are at risk for transmitting it to others," it said, citing "unpublished data" from the CDC COVID-19 Response Team. ![]() "Preliminary evidence suggests that fully vaccinated people who do become infected with the Delta variant can be infectious and can spread the virus to others," it said.Īn article published in the CDC's Morbidity and Mortality Weekly Report ( MMWR) on July 27 likewise did not back up Walensky's claim that vaccinated delta carriers have "the same capacity" to transmit the virus as unvaccinated carriers. The brief cited "early data" from India and "unpublished data" from the United States suggesting that "breakthrough Delta infections are transmissible." But it did not say they were as transmissible as infections in unvaccinated people. "These findings, along with the early evidence for reduced viral load in vaccinated people who develop COVID-19, suggest that any associated transmission risk is likely to be substantially reduced in vaccinated people." "COVID-19 vaccines currently authorized in the United States have been shown to be effective against SARS-CoV-2 infections, including asymptomatic and symptomatic infection, severe disease, and death," the CDC said. "The breakthrough infections, as rare as they are, have the potential to forward transmit with the same capacity as an unvaccinated person," Walensky told reporters on July 27, the day the CDC issued new guidance recommending that vaccinated people resume wearing face masks in public places if they live in "areas of substantial or high transmission." That statement contradicted a "science brief" that the CDC published the same day. That evidence includes a new study that found viral loads in vaccinated and unvaccinated COVID-19 patients were initially similar but dropped faster in the vaccinated group. Walensky's statements about the likelihood that vaccinated carriers will transmit the virus likewise have been inconsistent, confusing, and sometimes stronger than the evidence supports. While she has described so-called breakthrough infections as "rare" and this week reiterated the point that vaccinated people face a "far lower" infection risk than unvaccinated people, she also has offered an estimate implying the reverse: that vaccination somehow makes people more vulnerable to infection. Rochelle Walensky, director of the Centers for Disease Control and Prevention (CDC), has sent mixed messages about the likelihood that people vaccinated against COVID-19 will be infected by the delta variant of the coronavirus. ![]()
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