Impact of influenza vaccination on the risk of SARS-CoV-2 infection in a middle-aged group of people

Figures & data

Table 1. Characteristics of the study patients

	Vaccinated subjects n = 1108	Unvaccinated subjects n = 1450	P value
Mean age	53.7 ± 4.7	50.1 ± 6.8	0.49
Female (%)	686 (63)	782 (54)	0.21
BMI	21.7 ± 4.5	23.1 ± 5.1	0.19
Active smokers	387 (35)	459 (32)	0.41
Presence of chronic diseases	481 (43)	544 (38)	0.06
One	310	389
Two	116	109
More	55	46
Cardiovascular diseases*	281 (25)	315 (22)	0.13
COPD or asthma	178 (16)	185 (13)	0.09
Diabetes	107 (10)	124 (9)	0.28
Hyperlipidemia	113 (10)	100 (7)	0.17
Others	114 (10)	98 (7)	0.08
Rural living area	871 (79)	1090 (75)	0.44
BCG in childhood^	1073 (97)	1387 (96)	0.35

Legend: definition of chronic disease: confirmation by ICD-10 and a minimum of 6 months of documented treatment; * including arterial hypertension, heart failure, arrhythmias, coronary diseases; ^ BCG – compulsory vaccination against tuberculosis in early childhood.

Figure 1. Effect of influenza vaccination on SARS-CoV-2 infections in vaccinated and unvaccinated patients

Legend: blue curve – vaccinated patients, red curve- unvaccinated; * excluded analysis of first two weeks to avoid SARS-CoV-2 infections just after IV.

Table 2. Hazard ratios (HRs) for protection against SARS-CoV–2 infection comparing vaccinated beneficiaries with unvaccinated patients in relation to the analyzed confounding factors

Factors	HR	95% CI
Age 40–50 51–60	0.55 0.49 0.61	0.47–0.59 0.42–0.53 0.58–0.71
Sex	0.37	0.29–0.41
Comorbidities^a	0.83	0.68–0.78
High economic status^b	0.54	0.52−0.66
SARS-CoV–2 infection	0.74	0.54−0.89
Influenza infection in last year	0.53	0.49–0.57
Influenza vaccination in the past (minimum in previous season)	0.69	0.58–0.74
Pro-health behaviour^c	0.48	0.39–0.52
BCG vaccination	0.66	0.47–0.73

Legend: ^acomorbidities listed in Tables 1; ^bto have additional health insurance; ^cpreventive medical checkups in the last year.

Table 3. Patients hospitalized due to SARS-CoV-2 based on PCR confirmation

	Vaccinated subjects n = 6 (9%)	Unvaccinated subjects n = 15 (17%)	P value
Mean oxygen saturation on the day of submission	92.6 ± 2.8	90.1 ± 4.3	>0.05
Patients who needed MV	0	2	0.06
Days of MV	–	6 and 10
Average number of days of hospitalization (range)	16.3 (12–28)	17.5 (12–25)	0.08
Therapy:
Oxygen therapy	6	15
Remdesivir	1	6
Dexamethasone	2	12
Antibiotics	2	7
Low molecular weight heparin	6	15
The mean lowest oxygen saturation during hospitalization	89.3 ± 1.1	86.3 ± 2.8	0.05
Heart failure during hospitalization	1	6	0.03
Death from SARS-CoV-2 infection	0	1	0.07