Table 1.

Efficacy of primary COVID-19 vaccine cycle and vaccine boosters from the ongoing Italian nationwide COVID-19 vaccination campaign

	Unvaccinated	Vaccinated (≥ 5 months)	Vaccinated (< 5 months)
OR (95%CI) total SARS-CoV-2 infections
Vaccinated (≥ 5 months)	0.30 (0.2900.31; p < 0.001)	–	–
Vaccinated (< 5 months)	0.20 (0.19–0.21; p < 0.001)	0.66 (0.63–0.69; p < 0.001)	–
Vaccinated (Booster)	0.07 (0.06–0.08; p < 0.001)	0.25 (0.23–0.27; p < 0.001)	0.37 (0.35–0.40; p < 0.001)
OR (95%CI) COVID-19-related hospitalizations
Vaccinated (≥ 5 months)	0.17 (0.16–0.19; p < 0.0019	–	–
Vaccinated (< 5 months)	0.14 (0.13–0.15; p < 0.001)	0.80 (0.71–0.90; p < 0.001)	–
Vaccinated (Booster)	0.03 (0.02–0.04; p < 0.001)	0.17 (0.14–0.21; p < 0.001)	0.21 (0.17–0.26; p < 0.001)
OR (95%CI) COVID-19 related ICU admissions
Vaccinated (≥ 5 months)	0.10 (0.07–0.16; p < 0.001)	–	–
Vaccinated (< 5 months)	0.14 (0.10–0.21; p < 0.001)	1.41 (0.82–2.43; p = 0.210)	–
Vaccinated (Booster)	0.02 (0.01–0.04; p < 0.001)	0.18 (0.06–0.53; p < 0.001)	0.13 (0.04–0.37; p < 0.001)
OR (95%CI) COVID-19 related deaths
Vaccinated (≥ 5 months)	0.12 (0.10–0.14; p < 0.001)	–	–
Vaccinated (< 5 months)	0.12 (0.10–0.14; p < 0.001)	0.99 (0.81–1.22; p = 0.958)	–
Vaccinated (Booster)	0.02 (0.01–0.03; p < 0.001)	0.19 (0.13–0.27; p < 0.001)	0.19 (0.13–0.27; p < 0.001)

Statistically significant values (p < 0.05) are reported in bold

OR odds ratio, 95%CI 95% confidence interval, COVID-19 coronavirus disease 2019, ICU intensive care unit, SARS-CoV-2 severe acute respiratory syndrome coronavirus 2