A cluster of hundreds of COVID-19 cases on Cape Cod, many involving vaccinated people, prompted the Centers for Disease Control and Prevention (CDC) to change its policy on mask-wearing this week.
The July 4th outbreak in Provincetown, Massachusetts showed that vaccinated people infected with the Delta variant could spread the virus. A total of nearly 900 infections have been linked to the cluster.
The high viral load of the Delta variant, which was first discovered in India late last year, makes it possible for vaccinated who become infected through breakthrough cases to spread the virus in some cases, the CDC now says.
Of the initial 469 people infected, 346 (74 percent) were fully vaccinated, the CDC said in a presentation on Friday, July 30.
Seventy-nine percent of those 346 infected showed symptoms, the agency noted. There have been no deaths reported so far.
Of the five people hospitalized among the first 469 Cape Cod cases, four were fully vaccinated. Health experts say if so many had not been fully vaccinated, there could have been 100 or more hospitalizations.
“This finding is concerning and was a pivotal discovery leading to CDC’s updated mask recommendation," CDC Director Rochelle Walensky said on Friday.
“The war has changed,” the CDC presentation said.
Estimates are that the Delta variant is at least 50 times more contagious than the Alpha variant, which was initially discovered in the United Kingdom in September, 2020.
"In recent days I have seen new scientific data from recent outbreak investigations, showing that the delta variant behaves uniquely differently from past strains of the virus that causes COVID 19," Walensky said earlier in the week in announcing the new mask recommendations.
"Information on the Delta variants from several states and other countries, indicate that in rare occasion some vaccinated people infected with a delta variant after vaccination may be contagious and spread the virus to others. This new science is worrisome and unfortunately warrants an update to our recommendation."
The Delta variant is "more transmissible than the viruses that cause MERS, SARS, Ebola, the common cold, the seasonal flu, and smallpox, and it is as contagious as chickenpox," the CDC is now saying.
- Earlier report - COVID-19: Cape Cod Cluster Cases Nearly Double
- Original report - COVID-19: Cape Cod Cluster Linked To Delta Variant Grows To 430 Cases
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