The CDC research has several limitations and is only restricted to the Delta variant of COVID-19.
On July 30, 2021, the Centers for Disease Control and Prevention released new guidelines for people fully vaccinated against COVID-19. CDC suggested that everyone wears a mask, irrespective of their vaccination status, to prevent the transmission of the virus. The decision was based on recent research conducted by the CDC on the virus load of vaccinated and unvaccinated people infected with the Delta variant.
As a part of the research, 469 COVID-19 cases associated with multiple summer events in a town in Barnstable County, Massachusetts, were identified. The vaccination coverage among eligible Massachusetts residents was 69 percent. Approximately 364 people (74 percent) of cases occurred in people fully vaccinated with mRNA vaccines. Two hundred and seventy-four people (79 percent) vaccinated patients with breakthrough infection had symptoms. Also, out of five people who were hospitalized, four were fully jabbed. However, no deaths were reported. The research found that the RT-PCR cycle threshold (Ct) values in the 127 vaccinated people were similar to those from 84 unvaccinated people, not fully vaccinated, or whose vaccination status was unknown.
The research concluded that vaccinated and unvaccinated people would have similar viral loads of COVID-19 Delta variant infection, and even the vaccinated people infected with the Delta variant can transmit the virus.
A similar study conducted by the Nuffield Department of Medicine under the University of Oxford published the same results as CDC. The Delta infection resulted in equally high SARS-CoV-2 viral loads in the people with or without vaccination. However, the study noted that the vaccine would reduce the severity of the infection.
However, the CDC research report was subject to four limitations. According to the CDC, data from this report is not sufficient to conclude the effectiveness of COVID-19 vaccines against SARS-CoV-2. Also, the asymptomatic breakthrough infections could be underrepresented because of detection bias. Moreover, the demographics of cases likely reflect those of attendees at the public gatherings, as events were marketed to adult male participants. Most importantly, the Ct values can also be affected by factors other than viral load.
Considering the above study has so many limitations, further research is required to conclude the findings. Also, since the above analysis is limited to the Delta variant of COVID-19, it would be misleading to say that the virus load in vaccinated and unvaccinated people is the same.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19, including symptoms, prevention, and available treatment, please refer to the World Health Organization or your national healthcare authority.