This coincides with a recent study from the United States, where similar results were observed in Wisconsin.
“Some initial findings ... indicate that levels of virus in those who become infected with Delta having already been vaccinated may be similar to levels found in unvaccinated people,” PHE said in a statement.
“This may have implications for people’s infectiousness, whether they have been vaccinated or not,” it added. “However, this is early exploratory analysis, and further targeted studies are needed to confirm whether this is the case.”
The Delta variant, first identified in India, is currently the dominant CCP virus variant in England.
Ct value is the number of cycles needed to boost the viral signal in a sample when conducting an RT-PCR test.
The non-age-stratified data indicate that “whilst vaccination may reduce an individual’s overall risk of becoming infected, once they are infected there is limited difference in viral load (and Ct values) between those who are vaccinated and unvaccinated,” PHE said.
“Given they have similar Ct values, this suggests limited difference in infectiousness,” the document reads, adding that test-seeking behaviour and true changes in the data, such as the age distribution of cases, can influence the findings.
In a recent study from Wisconsin, the United States observed a similar result.
However, these findings contradict the findings of a recent study by Imperial College London (ICL).
Vaccines ‘May Be Less Effective’ Against Lambda Variant
In a separate statement, PHE said that “there is preliminary laboratory evidence to suggest that vaccination and previous infection may be less effective at preventing infection” with the Lambda (B.1.621) variant.“However, this data is very limited and more research is required. There is no evidence to suggest that [it] is more transmissible than the dominant Delta variant,” it said.
According to PHE, England has 37 confirmed cases of the Lambda variant.
The document also said there’s evidence indicating that the Lambda variant evades natural immunity from previous Delta infections.
Case numbers in the recent wave of infections peaked at a similar level to those seen in January, but the numbers of hospitalisations and deaths were far lower than those of the last wave.
There is currently no long-term data on the effectiveness and safety of the vaccines.