Using a physical model and aggregate data from Israel to estimate the current (July 2021 ) efficacy of the Pfizer-BioNTech vaccine

From the end of June 2021, the state of Israel, where 60% of the population is vaccinated with an mRNA BNT162b2 vaccine, has an increase in the daily morbidity. This increase may be a result of different events: a temporal decline of the vaccines efficacy; Lower efficacy of the vaccine against the current Delta ((B.1.617.2) variant (which is now the dominant strain in Israel); A result of lack of social restrictions, a highly contagious variant, or any combination of the above. We found, by using a novel spatial-dynamic model and recent aggregate data from Israel, that this new surge of cases is partiality due to a decline in the shielding of those who were vaccinated about six months ago. Also, we found a decrease in the vaccines efficacy against severe morbidity for the early elderly population compared to the rest of the vaccinated population. These results, which are consistent with recent studies, emphasize the high ability of the model in evaluating the time- and age- dependent efficacy of the vaccine for different age groups and enables to predict the spread of the pandemic as a function of such efficacy.