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Take a Load Off?

An initial analysis suggests that the Pfizer-BioNTech SARS-CoV-2 vaccine could reduce viral load and, in turn, perhaps viral transmission, the Guardian reports.

Researchers in Israel led by MyHeritage Lab's Yaniv Erlich compared PCR Ct values from December 2020 and January 2021 for individuals testing positive for SARS-CoV-2 who were over the age of 60 and those between the age of 40 and 60. Israel, the Guardian notes, rolled out its vaccination effort in late December 2020, first vaccinating older individuals, largely with the Pfizer-BioNTech BNT162b2 vaccine. 

As Erlich and his colleagues note in a preprint posted to MedRxiv, they hypothesized that if the vaccine leads to a decline in viral load, they should see a difference in Ct values between the groups beginning in January and not before. In their sample of 16,297 tests, they estimated that vaccination reduces viral load by 1.6 times to 20 times among individuals testing positive for SARS-CoV-2.

The Guardian notes that if a person's viral load is lower, the suspicion is that they would transmit the virus at a lower rate. Erlich cautions at the Guardian, though, that the analysis was initial one and that it is not yet established whether this decline in viral load would limit transmission.