The Centers for Disease Control and Prevention (CDC) has finally released the data behind recent backtracking on mask recommendations for vaccinated Americans to wear masks indoors at COVID-19 hotspots.
In a report published Friday, the federal health agency described a COVID-19 outbreak in Barnstable County, Massachusetts earlier this month linked to the spread of the Indian ‘Delta’ variant.
Researchers found that nearly three-quarters of infections occurred in people fully vaccinated against COVID-19 with one of three injections approved in the US
In addition, tests showed that immunized people had exactly the same viral levels in their nose and throat as unvaccinated people.
However, there were only four hospitalizations and no fatalities, showing that the vaccines are highly effective against serious illness and death.
A new CDC report details 469 cases of COVID-19 linked to an outbreak in Provincetown, Massachusetts between July 3 and July 17, with 74% of them in fully vaccinated people
For the report, the team looked at COVID-19 cases linked to summer events and large gatherings in Provincetown between July 3 and July 17.
Thousands of locals and tourists flocked to the summer city for Independence Day celebrations, as well as family vacations, busy bars, restaurants, rental properties and more.
On July 10, the Massachusetts Department of Public Health began receiving reports of an increased number of cases related to the county.
The 14-day moving average of COVID-19 cases in the country rose from zero cases per 100,000 people on July 3 to 177 cases per 100,000 people.
By July 26, 469 cases had been identified, of which 74 percent — or 346 — had been fully vaccinated with at least 14 days since their last dose.
Of these groups, 46 percent had received the Pfizer-BioNTech vaccine, 38 percent the Moderna vaccine and 16 percent the Johnson & Johnson vaccine.
The remaining 26 percent, or 84 cases, were among people who had not been vaccinated, had received only one dose, or whose vaccination status was unknown.
Results showed that vaccinated people who get COVID-19 have the same viral levels as unvaccinated
Nearly 80 percent of those with “breakthrough” infections had signs or symptoms such as a cough, fever or headache.
Of the five COVID-19 patients hospitalized, four were fully vaccinated, two of whom had underlying conditions.
No deaths were reported in either group.
To measure levels of the virus, CDC researchers looked at a figure known as the cycle threshold (Ct).
After an infected person is collected, the sample is isolated and must undergo several cycles of amplification to detect if there is any viral RNA.
The Ct value is the number of cycles it takes to detect the virus, after which the machine stops running. Any number below 30 is considered a high viral load.
There was virtually no difference in the Ct value between vaccinated and unvaccinated people.
Fully vaccinated patients had a Ct value of 22.77 while the unvaccinated group had a Ct value of 21.54.
Ideally, the number among vaccinated people should be above 35 and closer to 40, which would indicate low levels of the virus.
“The SARS-CoV-2 Delta variant is highly transmissible and understanding determinants of transmission, including human behavior and vaccine effectiveness, is critical to developing prevention strategies,” the authors wrote.
“Event organizers and local health jurisdictions should continuously assess whether additional measures are needed, including limiting capacity at meetings or postponing events, based on current spread rates of COVID-19, population vaccination rates and other factors. ‘