Background: During the months of August-October Israel has experienced the fourth wave of COVID-19 outbreak. This outbreak resulted in major increases in COVID-19 hospitalizations and mortality. At the beginning of this outbreak, Israel had one of the highest rates of two-dose Pfizer vaccination (2D protocol) and was beginning a vigorous campaign to promote a third-injection booster of the vaccine (3D protocol). Purpose: The official serious illness and deaths records were analyzed in order to assess the efficacy of the 2D and 3D protocols in preventing serious illness or death due to COVID-19 infection Methods: All raw data were obtained from the official Ministry of Health records (Data Dashboard). The same source was used to estimate the size of the relevant populations. The data for serious illness or mortality were normalized to sizes of the relevant populations on a daily basis.

Results and Conclusions: The 2D protocol alone, or followed by third-dose booster, significantly protected the relevant populations against serious illness (5 and 3-fold, respectively) and death (3.4 and 2.2-fold, respectively). However, this alternative analysis indicated that there was no protective advantage of the 3D over the 2D protocol. Actually, the protective effect of the 2D protocol against serious illness, and death in particular, appeared to exceed by a large factor that of the 3D protocol. Importantly, there was an unexpected early and prolonged rise in COVID-19 mortality in the 3D population. These results are discordant with the official statistics of the Ministry of Health and with some of the results presented in the scientific literature. Moreover, the kinetics of serious illness or mortality was spiking instead of the expected monotonous rise and decline, suggesting additional factors involved.