ABSTRACT
Background: Estimating real-world vaccine effectiveness is challenging as a variety of population factors can impact vaccine effectiveness. We aimed to assess the population-level reduction in cumulative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cases, hospitalizations, and mortality due to the BNT162b2 mRNA coronavirus disease 2019 (COVID-19) vaccination campaign in Israel during January-February 2021. Methods: A susceptible-infected-recovered/removed (SIR) model and a Dynamic Survival Analysis (DSA) statistical approach were used. Daily counts of individuals who tested positive and of vaccine doses administered, obtained from the Israeli Ministry of Health, were used to calibrate the model. The model was parameterized using values derived from a previous phase of the pandemic during which similar lockdown and other preventive measures were implemented in order to take into account the effect of these prevention measures on COVID-19 spread. Results: Our model predicted for the total population a reduction of 648 585 SARS-CoV-2 cases (75% confidence interval [CI], 25 877-1 396 963) during the first 2 months of the vaccination campaign. The number of averted hospitalizations for moderate to severe conditions was 16 101 (75% CI, 2010-33 035), and reduction of death was estimated at 5123 (75% CI, 388-10 815) fatalities. Among children aged 0-19 years, we estimated a reduction of 163 436 (75% CI, 0-433 233) SARS-CoV-2 cases, which we consider to be an indirect effect of the vaccine. Conclusions: Our results suggest that the rapid vaccination campaign prevented hundreds of thousands of new cases as well as thousands of hospitalizations and fatalities and has probably averted a major health care crisis.
ABSTRACT
BACKGROUND: Benefits of school reopening must be weighed against the morbidity and mortality risks and the impact of enhancing spread of coronavirus disease 2019 (COVID-19). We investigated the effects of school reopening and easing of social-distancing restrictions on dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in Israel between March and July 2020. METHODS: We examined the nationwide age-wise weekly incidence, prevalence, SARS-CoV-2 polymerase chain reaction tests, their positivity, COVID-19 hospitalizations, and associated mortality. Temporal differences in these parameters following school reopening, school ending, and following easing of restrictions such as permission of large-scale gatherings were examined. RESULTS: Incidence of SARS-CoV-2 infections gradually increased following school reopening in all age groups, with a significantly higher increase in adults than children. Higher rate ratios (RRs) of sample positivity rates 21-27 days following school reopening relative to positivity rates prior to openings were found for the age groups 40-59 (RR, 4.72; 95% CI, 3.26-6.83) and 20-39 (RR, 3.37 [2.51-4.53]) years, but not for children aged 0-9 (RR, 1.46 [.85-2.51]) and 10-19 (RR, .93 [.65-1.34]) years. No increase was observed in COVID-19-associated hospitalizations and deaths following school reopening. In contrast, permission of large-scale gatherings was accompanied by increases in incidence and positivity rates of samples for all age groups, and increased hospitalizations and mortality. CONCLUSIONS: This analysis does not support a major role of school reopening in the resurgence of COVID-19 in Israel. Easing restrictions on large-scale gatherings was the major influence on this resurgence.