Results
Booster Dose Vaccination Campaign
By October 31, 2021, persons ≥60 years of age reached a vaccination rate of ≈80% (Appendix Figure 1). Vaccination rates by that date were 70.2% for the 50–59-year age group, 62.4% for the 40–49-year age group, 53.1% for the 30–39-year age group, and 44.7% for the 16–29-year age group (Appendix Figure 1).
Booster Dose VE in Persons 16–59 Years of age
Adjusted VE point estimates reached 92.8% (95% CI 91.3%–94.0%) in week 2 of the evaluation period and 96.8% (95% CI 96.0%–97.5%) by week 3 (Figure 2, panel A; Appendix Table 3). The adjusted VE remained above 95% until week 10 and thereafter started to slowly decline, reaching VE of 89.6% (95% CI 85.4%–92.7%) in week 14. In weeks 15 and 16, VE point estimates declined by 12%, reaching a point estimate of 77.6% (95% CI 68.4%–84.2%) (Figure 2, panel A; Appendix Table 3). The evaluation dates of weeks 15 and 16 occurred during December 2021 (Appendix Table 2), when the percentage of the B.1.1.529 (Omicron) variant among reported sequenced samples in Israel rapidly increased (Figure 3).[9] VE estimation by age groups demonstrated similar patterns (Appendix Figure 4).
Booster Dose VE in Persons ≥60 Years of age
Adjusted VE point estimates reached 76.4% (95% CI 70.9%–80.9%) on week 2 of the evaluation period and 93.1% (95% CI 91.8%–94.2%) by week 3 (Figure 2, panel B; Appendix Table 3). The adjusted VE remained above 93% until week 13, and thereafter started to slowly decline, reaching VE of 90.6% (95% CI 87.2%–93.1%) at week 17. In weeks 18 and 19, VE point estimates declined by 7% and in week 20, VE declined by 21.6%, reaching a point estimate of 61.3% (95% CI 52.5%–68.4%) (Figure 2, panel B; Appendix Table 3). The evaluation dates of weeks 19 and 20 occurred during December 2021 (Appendix Table 2), when the percentage of the B.1.1.529 (Omicron) variant among reported sequenced samples in Israel rapidly increased (Figure 3).[9]
Hospitalizations Among SARS-CoV-2–Positive Booster Dose Vaccine Recipients
We analyzed rate reductions of hospitalizations among persons who became SARS-CoV-2-positive by week and for all evaluation weeks combined (Table 1). The hospitalization rate reduction by week for persons 16–59 years of age was between 62.8% (95% CI −0.6% to 86.2%) and 100.0%. The combined rate reduction for weeks 2–16 was 89.2% (95% CI 79.1%–94.4%) (Table 1).
The hospitalization rate reduction by week for persons ≥60 years of age was between 54.9% (95% CI −35.9 to 85.1%) and 95.0% (95% CI 72.1%–99.1%). The combined rate reduction for weeks 2–20 was 75.1% (95% CI 71.3%–78.5%) (Table 1).
Severe Disease Among SARS-CoV-2–Positive Booster Dose Vaccine Recipients
The severe or critical disease rate reduction for persons 16–59 years of age was 92.0% (95% CI 70.0%–97.9%) on week 2 (Table 2). No cases of severe or critical disease were recorded among booster-dose recipients for weeks 3–16. The combined rate reduction for weeks 2–16 was 97.3% (95% CI 89.7%–99.3%) (Table 2).
The rate reduction of severe or critical disease by week for persons ≥60 years of age was between 58.6% (95% CI 11.1%–80.7%) and 100%. The combined rate reduction for weeks 2–20 was 81.6% (95% CI 78.3%–84.3%) (Table 2).
Deaths Among SARS-CoV-2-Positive Booster Dose Vaccine Recipients
No deaths were recorded among booster-dose recipients 16–59 years of age during the evaluation weeks, compared with 1–45 deaths per week in the unvaccinated group, a rate reduction of 100% (Table 3). The death rate reduction by week for persons ≥60 years of age was between 49.1% (95% CI −44.3% to 82.1%) and 100%. The combined rate reduction for weeks 2–20 was 77.1% (95% CI 71.2%–81.8%) (Table 3). Analysis of death rate reduction by using only deaths that were highlighted by hospitals as deaths caused by COVID-19 and limiting the time from positive PCR test to death by up to 28 days yielded similar results (Appendix Tables 4, 5).
Emerging Infectious Diseases. 2022;28(5):948-956. © 2022 Centers for Disease Control and Prevention (CDC)
