Table 2. Adjusted vaccine effectiveness in the primary and secondary analyses, VEBIS healthcare worker multicentre cohort study on COVID-19 vaccine effectiveness, seven European countries, season 2023/24 (n = 1,305).

Analysis	Vaccinated			Unvaccinated			Adjusteda CVE
	Number HCWs	Events	Person-days	Number HCWs	Events	Person-days
Overall effect
SARS-CoV-2 infection	300	37	35,657	1,130	207	121,394	22 (−17 to 48)
Asymptomatic infection	300	15	35,657	1,130	101	121,394	26 (−43 to 61)
Symptomatic COVID-19	300	22	35,657	1,130	106	121,394	17 (−40 to 51)
By recent prior infection
No recent prior infection	184	25	21,135	738	150	70,024	33 (−9 to 58)
Recent prior infection	92	8	9,848	486	53	48,601	−9 (−139 to 50)
Time since previous vaccination
Vaccinated 90–365 days before the current season vaccination	300	37	35,657	165	10	5,186	−31 (−245 to 50)
Vaccinated > 365 days before the current season vaccination	300	37	35,657	1,082	197	116,208	23 (−16 to 49)
Before/after BA.2.86 predominant circulation and time since vaccination in season
Before	190	9	4,999	871	108	36,503	49 (−8 to 76)
7–59 days vs > 365 days before	190	9	4,854	801	100	32,278	47 (−11 to 75)
≥ 60 days vs > 365 days before	21	0	145	801	100	32,278	Not calculated
After	296	28	30,658	963	99	84,891	−11 (−84 to 34)
7–59 days vs > 365 days before	231	9	5,849	958	97	83,930	16 (−88 to 63)
≥ 60 days vs > 365 days before	283	19	24,809	958	97	83,930	−25 (−128 to 31)
Time since vaccination in season vs > 365 days before
7–59 days	267	18	10,703	1,082	197	116,208	24 (−29 to 55)
60–119 days	251	9	6,658	1,082	197	116,208	39 (−43 to 74)
120–149 days	243	9	16,080	1,082	197	116,208	−2 (−114 to 52)

CVE: COVID-19 vaccine effectiveness; HCW: healthcare worker; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.

^a Adjusted by age sex, site, at least one underlying condition, recent previous SARS-CoV-2 infection (Participants with at least one covariate missing were not included in the adjusted model).