Time lapses between distribution of influenza vaccines to health authorities and their administration by General Practitioners (GPs) to older adults: a retrospective study over five influenza seasons in Italy

Figures & data

Table 1. Characteristics of the overall older adult population and the amount of influenza vaccine doses delivered and administered over 5 influenza seasons in Italy.

	Influenza season
N	2017–2018	2018–2019	2019–2020	2020–2021	2021–2022
Total resident population (aged 15–95 years)^b	51,862,355	51,833,341	51,794,400	51,479,434	51,540,338
Resident older adults (aged 65–95 years)^a	13,487,719	13,581,770	13,739,556	13,821,297	13,927,447
Weeks	29	31	31	32	17
GPs in HSD	1129	1111	1096	1085	1064
Total population under care of GPs in HSD	1,346,465	1,287,476	1,223,344	1,174,423	1,058,289
Older adults under care of GPs in HSD	362,023	350,440	337,929	322,907	288,401
Male	160,320	155,634	151,480	145,928	133,103
Female	201703	194806	186449	176979	155298
Influenza vaccines
Delivered doses	3,004,521	2,847,156	3,235,771	6,035,439	5,947,126
Expected doses^b	78,455	73,226	78,974	137,787	120,821
Administered doses	87,316	89,955	99,384	114,253	85,815

Abbreviations: GP, general practitioner; HSD, health search database.

^aAs per https://demo.istat.it/.

^bThe calculation involves, for each season, multiplying the number of older adults under the care of GPs by the ratio of doses delivered to the total number of older adults as indicated in official demographic reports on regional bases.

Figure 1. Trends in influenza vaccine distribution to regional authorities and vaccine administration by general practitioners by influenza season.

Table 2. Vaccine distribution and vaccine administration velocities and vaccine coverage over 5 influenza seasons in Italy.

Influenza season	Velocity, median doses/week (IQR)			Vaccine coverage (%)
	Distribution	Administration	Difference^c
2017–2018	518 (235–925)	176 (106–408)	395 (108–777)	23.65
2018–2019	341 (102–675)	209 (88–348)	289 (110–551)	24.51
2019–2020	466 (159–952)	152 (96–299)	304 (200–669)	28.49
2020–2021	740 (261–1360)	203 (102–351)	622 (216–971)	36.53
2021–2022	833 (242–1514)	270 (112–499)	431 (167–1068)	30.75
p value over 5 seasons^c	0.421	0.065	0.189	0.142

Abbreviations: IQR, interquartile range (25th-75th percentile); MAH, marketing authorization holder; SD, standard deviation; ‘week’ is the observation time unit for each influenza seasons.

^aFrom MAH data weighted by official demographics.

^bDifference between distribution and administration rates (analyses are clustered by region of residence and then inferred to the Italian cohort).

^cTest on median clustered by regions of residence.

Table 3. Association between difference of distribution and administration velocities (doses/week of influenza vaccines) and hospital admissions over 5 influenza seasons according to quantile (median) regression.

	All-cause hospitalizations					Respiratory-related hospitalizations
Influenza season	Hospital admissions (n)	Vaccinees (n)	Cumulative incidence (%)	β^a (95% CI)	p value	Hospital admissions (n)	Vaccinees (n)	Cumulative incidence (%)	β^a (95% CI)	p value
2017–2018	3303	87,316	3.78	0.10 (0.01–0.20)	0.034	179	87,316	0.21	0.01 (0.1–0.2)	0.014
2018–2019	3899	89,955	4.33	0.54 (0.10–1.20)	0.030	211	89,955	0.22	0.03 (0.01–0.06)	0.034
2019–2020	4373	99,384	4.40	0.45 (−0.12 to 1.01)	0.185	212	99,384	0.21	0.01 (−0.02 to 0.03)	0.524
2020–2021	4283	114,253	3.75	0.12 (0.01–0.22)	0.030	263	114,253	0.23	0.01 (0.001–0.013)	0.016
2021–2022	899	85,815	1.05	0.01 (−0.1 to 0.05)	0.854	21	85,815	0.02	—^b	—
Pooled estimate^c				0.10 (0.01–0.20)

Abbreviations: CI, confidence interval.

^aProportional (%) increase or decrease versus the median value of the outcome for each individual vaccine dosage/day.

^bReduced analysis power for low number of hospital admissions (n = 21).

^cMeta-analysis using random effect model.