The Centers for Disease Control and Prevention (CDC) has finally released the data that was behind its recent backtrack on mask recommendations for vaccinated Americans to wear masks in indoor places in COVID-19 hot spots.
In a report published on Friday, the federal health agency detailed a COVID-19 outbreak earlier this month in Barnstable County, Massachusetts linked to the spread of the Indian ‘Delta’ variant.
Researchers found nearly three-quarters of the infections occurred in people who were fully vaccinated against COVID-19 with either of three shots approved in the U.S.
What’s more, tests showed that immunized people carried just the same viral levels in their noses and throats as unvaccinated people did.
However, there were just four hospitalizations and no fatalities, showing that the vaccines are very effective against severe disease and deaths.
A new CDC report detailed 469 cases of COVID-19 linked to an outbreak in Provincetown, Massachusetts between July 3 and July 17, of which 74% were 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 residents and tourists flocked to the summer town for Independence Day celebrations as well as family vacations, crowding bars, restaurants, rental homes and more.
On July 10, the Massachusetts Department of Public Health began receiving reports of an increased number of cases linked to the county.
The 14-day rolling average COVID-19 cases in the country rose from zero cases per 100,000 persons on July 3 to 177 cases per 100,000 person.
By July 26, 469 cases had been identified, of which 74 percent – or 346 – were among fully vaccinated with at least 14 days since their final dose.
Among this groups 46 percent had received the Pfizer-BioNTech vaccine, 38 percent the Moderna vaccines and 16 the Johnson & Johnson vaccine.
The remaining 26 percent, or 84 cases, were among people who were unvaccinated, had only received at least one dose or whose vaccination status was unknown.
Results showed that vaccinated people who get COVID-19 have same viral levels as the unvaccinated
Nearly 80 percent of those with ‘breakthrough’ infections had signs or symptoms such as cough, fever or a headache.
Of the five COVID-19 patients who were hospitalized, four were fully vaccinated of whom two 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) value.
After an infected person is swabbed, the sample is isolated and has to undergo under several amplification cycles to detect if there is any viral RNA.
The Ct value is the number of cycles necessary to spot the virus at which point the machine will stop running. Any number under 30 is considered a high viral load.
There was virtually no difference in the Ct value between vaccinated and unvaccinated people.
Fully vaccinated patients has 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 higher than 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 continually assess the need for additional measures, including limiting capacity at gatherings or event postponement, based on current rates of COVID-19 transmission, population vaccination coverage, and other factors.’