The Centers for Disease Control and Prevention (CDC) in its internal presentation has claimed that Delta variant of COVID-19 is as contagious as Chickenpox. The Washington Post has obtained the information from CDC and reported that vaccines may be less effective at preventing transmission of the Delta variant.
Vaccines are surely considered as highly effective against other variants of COVID-19, but might not work with the same efficiency in preventing infection caused by the Delta variant. This conclusion was drawn after reviewing published and unpublished data on Delta variant, leading CDC to comment: "Acknowledge the war has changed."
SARS, MERS VS Delta Variant
A report in Live Science stated that the Delta variant is more contagious than viruses that cause Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS), Ebola, the common cold, seasonal flu, the 1918 flu and smallpox. Report stated that Delta is as transmissible as Chickenpox.
An outbreak of Delta in Barnstable County, Massachusetts, showed both vaccinated and unvaccinated people were equally affected by the Delta variant. Currently, researchers are trying to find out if all of those virus particles are infectious, or the fraction that can infect others is the same for vaccinated versus unvaccinated people.
Data collected from England, Scotland, Canada and Israel show that Pfizer-BioNTech vaccine's effectiveness in preventing hospitalization is between 93 percent and 100 percent but in terms of Delta variant, vaccine-effectiveness is said to be between 64 percent and 88 percent, reported Live Science.
Cape Code Outbreak
Another shocking report from Cape Code proved the severity of Delta variant. Reports claimed that at least 350 vaccinated people have tested positive for COVID-19, mostly caused by the Delta variant. A total of 469 cases of COVID-19 were reported from Massachusetts, most cases  found in Cape Cod.
Science News stated that of these cases, 346 [amounting to 74 percent] were fully vaccinated. About 46 percent of them had received the Pfizer vaccine, 38 percent had received the Moderna vaccine and 16 percent had received the Johnson and Johnson vaccine. Breakthrough cases were mostly found among men [87 percent] of average 42 years.
After swab sample analysis from 133 cases, 90 percent were found to be infected with the Delta variant. On analysing 211 cases, health officials also found that CT value [proxy value for viral load] was found in same amount among vaccinated and unvaccinated people.
This outbreak in Cape Code led CDC announce new mask guidelines. As other mitigation measures are not in place yet, CDC in its latest presentation emphasized the use of mask. CDC stated: "Given higher transmissibility and current vaccine coverage, universal masking [including vaccinated people] is essential to reduce transmission of the delta variant."