Table 3. COVID-19-related hospitalisation and death rates by exposure status, and absolute and relative COVID-19 vaccine effectiveness estimates, Portugal, 15 May–31 July 2022 (n = 2,626,174).

Exposure status	Person-years	Events	Rate per 100,000 person-years	VE (95% CI)	rVE second booster and first relative to other vaccination regimens (95% CI)	rVE second booster relative to first booster (95% CI)
≥ 80 year-olds
Hospitalisation
Unvaccinated	10,901	164	1,505	Reference	NA	NA
Primary series	10,491	188	1,792	56 (46–65)	Reference	NA
First booster	61,637	858	1,392	63 (55–70)	16 (1–28)	Reference
Second booster	39,633	133	336	81 (75–85)	53 (43–65)	47 (35–57)
Death
Unvaccinated	10,911	231	2,117	Reference	NA	NA
Primary series	10,503	274	2,609	58 (49–65)	Reference	NA
First booster	61,702	1,209	1,959	64 (57–69)	13 (1–24)	Reference
Second booster	39,646	261	658	82 (77–85)	56 (47–63)	49 (41–56)
60–79 year- olds
Hospitalisation
Unvaccinated	31,482	94	299	Reference	NA	NA
Primary series	48,566	113	233	67 (56–75)	Reference
First booster	341,824	533	156	74 (66–80)	21 (2–36)
Death
Unvaccinated	31,491	67	213	Reference	NA	NA
Primary series	48,578	120	247	59 (44–70)	Reference
First booster	341,875	523	153	65 (54–74)	14 (−5 to 30)

COVID-19: coronavirus disease; NA: not applicable; rVE: relative vaccine effectiveness; VE: vaccine effectiveness.