The study by Israeli researchers has not been published and peer-reviewed. It is early to ascertain results at this stage of the research.
Israel's largest coronavirus testing lab, MyHeritage lab, pre-published its findings of a study that shows that the Pfizer-BioNTech vaccine reduced viral load among those vaccinated. With one of the fastest COVID-19 vaccination drive, Israel has administered the Pfizer-BioNTech vaccine to nearly all of its eligible population.
The study compared data from 16,297 people over 60 years old and those aged between 40 to 60 who tested positive for the coronavirus between December 1, 2020, and January 30, 2021. The study found that 75 percent of individuals over 60 years had received their first dose at the time of the research, compared to 25 percent between 40 and 60. After January 15, esearchers saw a significant fall in the viral load for the individuals aged over 60, compared with the 40-60 group, which according to them, shows the vaccine is likely to reduce viral shedding and therefore decrease the spread in the community. The researchers used demographic data and daily vaccination rates to estimate the effect of vaccination on viral load shedding and calculated that "vaccination reduces the viral load by 1.6x to 20x in individuals who are positive for SARS-CoV-2," noting that "this estimate might improve after more individuals receive the second dose."
However, the researchers also stated that these are preliminary findings and have not been published and peer-reviewed. The results are also only based on partial data as the researchers were not aware if individuals in the study have been vaccinated.
Stephen Griffin, associate professor at Leeds University's school of medicine, told The Guardian that "the data, though early, was positive but not definitive." Washington Post also reported that "there’s insufficient data available to gauge the ability of vaccines to prevent people from developing asymptomatic infections or transmitting the virus to others. The quantity of infectious virus people “shed,” or emit in respiratory particles, is an indicator of their propensity to spread it".
With the study from Israel being at an initial stage and is yet to be published/peer-reviewed, we cannot corroborate the claim. Therefore, the claim is unverifiable.
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 Organisation or your national healthcare authority.