One of the key questions regarding COVID19 vaccines is whether they can reduce viral shedding . To date, Israel vaccinated substantial parts of the adult population, which enables extracting real world signals . The vaccination rollout started on Dec 20th 2020, utilized mainly the BNT162b2 vaccine, and focused on individuals who are 60 years or older . By now, more than 75% of the individuals of this age group have been at least 14 days after the first dose, compared to 25% of the individuals between ages 40-60 years old . Here, we traced the Ct value distribution of 16,297 positive qPCR tests in our lab between Dec 1st to Jan 31st that came from these two age groups . As we do not have access to the vaccine status of each test, our hypothesis was that if vaccines reduce viral load, we should see a difference in the Ct values between these two age groups in late January but not before . Consistent with this hypothesis, until Jan 15th, we did not find any statistically significant differences in the average Ct value between the groups . In stark contrast, our results in the last two weeks of January show a significant weakening in the average Ct value of 60+ individuals to the 40-60 group . To further corroborate these results, we also used a series nested linear models to explain the Ct values of the positive tests . This analysis favored a model that included an interaction between age and the late January time period, consistent with the effect of vaccination . We then used demographic data and the daily vaccination rates to estimate the effect of vaccination on viral load reduction . Our estimate suggests that vaccination reduces the viral load by 1.6x to 20x in individuals who are positive for SARS-CoV-2 . This estimate might improve after more individuals receive the second dose . Taken together, our findings indicate vaccination is not only important for individual's protection but can reduce transmission.