Seroprevalence of Toxoplasmosis in France: First Study in 1,995 Blood Donors

Abstract

The seroprevalence of toxoplasmosis is well-described in French pregnant women, but no data are available in the general population. This study investigated 1,995 blood donors (sex ratio = 1), aged 18 to > 70 years (mean 44.8). The seroprevalence was 50.9% and increased with age, reaching almost 90% in blood donors > 70. Men exhibited a higher seroprevalence than women in age group 30–39 (41.1% vs 27.6%, p = 0.033). Multivariate analysis confirmed that men were more likely to be infected than women (OR = 1.234, p = 0.036). The highest prevalences for Toxoplasma were observed in the Northern and South-Western regions of France (55.2 to 60.5%). The lowest prevalence was observed in the East (41.4%), and was significantly higher in men < 40 years compared to women. These data are consistent with prevalence studies conducted in French pregnant women, but shows for the first time that females are less frequently infected than males, particularly in some regions, which could motivate further epidemiological investigations.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44197-026-00565-4.

Introduction

Toxoplasmosis is a cosmopolitan zoonotic infection caused by an intracellular protozoan, Toxoplasma gondii [1]. Cats and other felids are the definitive hosts of the parasite while humans, as well as all warm-blooded animals, are intermediate hosts. Toxoplasma is transmitted through the ingestion of water, food or soil, contaminated by oocysts which have been previously spread into the environment by felids faeces. Intermediate hosts then undergo a systemic dissemination of tachyzoites through the blood stream, resulting in the persistence of encysted parasites in muscles, brain and eyes. As a result, infection can also occur through the ingestion of undercooked meat of intermediate hosts harbouring tissue cysts. Primary infection with Toxoplasma gondii in human is usually benign or asymptomatic in healthy individuals, except when patients are infected with a virulent genotype strain. By contrast, toxoplasmosis is a life-threatening infection in immunocompromised patients, such as HIV-infected patients or transplant patients. It can also be acquired through transplantation to a naïve donor of an infected organ containing cysts, or through blood transfusion if it contains tachyzoites [1]. Vertical transmission to the foetus can happen when toxoplasmosis is acquired during pregnancy, a situation where tachyzoites disseminate through the bloodstream and pass through the placental barrier.

It is estimated that one third of the population is infected by Toxoplasma gondii, but the seroprevalence varies widely between countries from 10 to 80%, and sometimes within a given country [2]. Low seroprevalence, below 30%, has been observed in North America and Northern Europe, South East Asia and the Sahelian region of Africa. In Central and Southern Europe prevalence is usually moderate (30–50%), while high prevalences have been reported in warm and humid areas such as Latin America and tropical African countries [1, 3, 4]. In developed countries, contamination seems to be essentially linked to the consumption of infected meat [5]. In Europe, prevalence varies according to dietary factors, as prevalence is lower in countries where meat is eaten well-cooked (UK, Scandinavia), and higher in France due to the consumption of rare or smoked meat.

Several studies have focused on the seroprevalence of T. gondii among pregnant women [6–10], but this specific group is not representative of the French population as a whole. To the best of our knowledge, no seroprevalence studies have focused on French blood donors. Therefore, this study aimed to estimate the prevalence of toxoplasmosis in blood donors, to complete French epidemiological data.

Material and Methods

Sample Collection

This is a retrospective study conducted at Rennes University Hospital (Rennes, France), aiming at assessing the seroprevalence of toxoplasmosis in French metropolitan blood donors. Sera were obtained through donation by the blood French establishment (Etablissement Français du Sang, EFS) before destruction. Sera were collected from adult individuals during blood donation and stored for usual serologic screening to secure blood-derived products. The donation to Rennes University Hospital was exhaustive, and consisted of all sera collected during every single blood donation in all French regions, overseas territories excluded, between July 1 st and December 31 st 2019.

For each serum, available informations were: sex, age range by decade (as the date of birth was not precisely known), and department/region of France where blood donation took place.

Serological Tests

All sera were included in the study and tested for anti-Toxoplasma IgG and IgM antibodies using the Platelia® Toxo IgG and Platelia® Toxo IgM (Bio-Rad, Marnes-la-Coquette, France). In case of doubtful results for IgG (IgG titer in the range 6–8 IU/mL) and/or doubtful or positive IgM (IgM index in the range 0.8–0.999) using these kits, a confirmation technique was performed, using the VIDAS® Toxo IgG II and VIDAS® Toxo IgM (BioMérieux, Marcy-l’Etoile, France), respectively. When IgG remained doubtful with both previous techniques, a western blot (WB) was performed using the Toxo II IgG confirmation kit (LD Bio Diagnostics, Lyon, France), and interpreted according to the manufacturer’s recommendations. All IgM-positive sera with simultaneous IgG detection benefited from an IgG avidity assay using the VIDAS® Toxo IgG Avidity kit (BioMérieux). A high avidity ≥ 0.300 can exclude primary infection within the last 4 previous months, while low avidity < 0.200 may suggest recent infection with T. gondii. An intermediate avidity between 0.200 and 0.299 is inconclusive.

Toxoplasma infection was defined by the presence of specific anti-Toxoplasma IgG with or without specific IgM.

Statistics

The mean age of the study population was calculated by multiplying the number of blood donors by the midpoint value of each age category, divided by the total number of donors. Prevalences were compared across categories (age class, sex, region of residency) using a Chi-squared test, or a Z test (age class, sex). Statistics were made using GraphPad Prim v10.1 software.

A multivariable logistic regression model was then performed to estimate adjusted odds ratios (ORs) and their 95% confidence intervals (95% CI). The reference categories were 18–29-year-old, female, and Grand-Est, for age, sex and region, respectively. Statistical significance was assessed using a two-sided threshold of p < 0.05. Model fit was evaluated using the likelihood ratio test and McFadden’s pseudo-R². Multivariable analysis was performed using Python, with pandas library for data management and statsmodels for statistical modelling.

Ethics approval

Blood donations are made voluntarily to the EFS, and donors give their consent for their use, including serological testing. The study adhered to the Declaration of Helsinki. Samples are anonymized and only a few data remain associated to the sample. Additionally, the study was approved by the ethics committee of the University Hospital of Rennes (approval number #25.153), which waived the necessity to inform blood donors of the reuse of their blood for secondary study, in relation to the strictly anonymized process and to French regulation (article L. 1211–2 du Code de la Santé Publique).

Results

In total, 1,995 sera were collected from healthy blood donors from the 12 regions of France. Platelia® Toxo IgG were positive and doubtful in 1,010 and 8 cases, respectively, while Platelia® Toxo IgM were doubtful or positive in 133 and 40 sera, respectively (8.7%). Those sera needed to be confirmed by VIDAS® Toxo IgG (n = 8) or VIDAS® Toxo IgM (n = 173). Thirty-two IgM and 5 IgG results were confirmed positive (24 IgM results; 2 IgG results) or doubtful (8 IgM results; 3 IgG results) with VIDAS® (sup. Table S1). Three sera with doubtful IgG results with both techniques were confirmed positive using the WB. An IgG avidity test was performed on all sera with positive IgG associated with positive or doubtful IgM (n = 32), of which 26 (81%) had high IgG avidity (infection dating more than 4 months ago), 4 had low IgG avidity and 2 were in the grey zone, thus recent infection could not be excluded.

Overall, of the 1,995 blood donors, 50.9% (n = 1,015) had IgG antibodies against Toxoplasma gondii (IgG +/IgM-, n = 983; IgG +/IgM +, n = 32). Anti-Toxoplasma IgM was never the sole positive test ever (IgG-/IgM +; n = 0).

The age of donors ranged from 18 to over 70 years; their mean age was 44.8 years. An equivalent number of sera was analysed in all age groups between 18 and 69, with a mean number of 381 ± 16 sera per age group. The sex ratio (M/F) was around 1 in all age categories (0.95–1.09) (Table 1). Blood donors aged 70 and older were fewer than in the younger groups (n = 90). A dramatic increase was observed according to age, from < 20% in the 18–29 age group to almost 90% in the > 70 group (p < 0.001) (Fig. 1, Table 1). Of the 1,015 positive sera, 531 and 484 were obtained from men and women, respectively. Overall, no differences in seroprevalence according to gender were observed (53.3% in males vs 48.7% in females, p = 0.083). However, seroprevalence was more frequently seropositive in men than in women in the age group 30–39 (41.1% vs 27.6% in men and women, respectively, p = 0.033), whereas the prevalence was not statistically different in all other age groups by univariate analysis (Table 1).

Table 1.

Toxoplasma seroprevalence among blood donors by age and gender, France, 2019 (n = 1,995)

Age groups years (N)	Seroprevalence %	Sex Ratio M/F	Seroprevalence in males		Seroprevalence in females		p valuea
			n/N	%	n/N	%
18–29 (N = 396)	18.4	0.95	38/193	19.7	36/203	17.7	0.777
30–39 (N = 384)	34.4	1.00	79/192	41.1	53/192	27.6	0.033
40–49 (N = 395)	53.7	1.01	107/199	53.7	105/196	53.6	0.974
50–59 (N = 371)	68.2	1.03	134/188	71.3	118/183	64.5	0.200
60–69 (N = 359)	74.1	0.99	130/179	72.6	136/180	75.6	0.561
70–71b (N = 90)	87.8	1.09	43/47	91.5	36/43	83.7	0.271
Overall (N = 1,995)	50.8	1.00	531/998	53.2	484/997	48.5	0.083

n Number of positive sera; N Number of tested sera; M Male; F Female

^aZ test

^bIndividuals are allowed to donate blood until the age of 71

Fig. 1.

Age-dependent Toxoplasma seroprevalence among blood donors per 10-year age group (right axis) and number of sera with IgG +/IgM-, IgG +/IgM + results and total number analysed per age group (left axis), France, 2019 (n = 1,995)

The four blood donors with low IgG avidity (< 0.200) were aged less than 50 years old, and were observed in different age groups (2 in the 18–29, 1 in the 30–39, and 1 in the 40–49 age group). They were observed equally in men and women, and in three distinct French regions, thus were not grouped cases.

We then compared the seroprevalence for toxoplasmosis according to the place of residence of blood donors. Only 13 to 27 sera (median = 21) were collected in each French department, thus analysis by department was not carried out as sample sizes were too small. The number of sera analysed by French region varied from 38 to 267 (median = 123). Blood donations per region ranged from 1.3 to 11.2 donations per 100,000 inhabitants (Table 2). The highest prevalences (> 55%) for Toxoplasma gondii were observed in the Northern and South-Western regions of France: Corse (60.5%), Hauts-de-France (56.4%), Nouvelle-Aquitaine (56.3%) and Ile-de-France (55.2%). The lowest prevalences (< 45%) were observed in the Eastern regions of the country: Grand-Est (41.4%), and Auvergne-Rhône-Alpes (44.2%) (Fig. 2). Univariate analysis showed that in Grand-Est, seroprevalence was significantly higher in males than in females, in the age group < 40 years (25.0 vs 6.3% respectively, p = 0.027), while in Hauts-de-France, it was higher in males than in females aged > 40 (89.3 vs 56.0% respectively, p = 0.015) (Table 3). Overall, in people < 40-year-old, males were more frequently Toxoplasma-seropositive than female in all regions, except Corse and Ile-de-France (Table 3).

Table 2.

Total blood donations per region per 100,000 inhabitants between June 1 st and December 31 st 2019

Region	Total population*	Total blood donation	Blood donation per 100,000 inhabitants
Auvergne-Rhône-Alpes	8,042,936	258	3.2
Bourgogne-Franche-Comté	2,805,580	177	6.3
Bretagne	3,254,854	83	2.5
Centre-Val de Loire	2,573,180	123	4.8
Corse	340,440	38	11.2
Grand Est	5,556,219	227	4.1
Hauts-de-France	6,004,947	94	1.6
Ile-de-France	12,262,544	154	1.3
Normandie	3,325,032	91	2.7
Nouvelle-Aquitaine	6,010,289	252	4.2
Occitanie	5,933,185	267	4.5
Pays de la Loire	3,806,461	108	2.8
Provence-Alpes-Côte d’Azur	5,081,101	123	2.4

^*Data: INSEE, 2019 population census

Fig. 2.

Toxoplasmosis prevalence among blood donors by region of residency, France, 2019 (n = 1,995). The prevalence (%), and the positive sera/total of analysed sera are shown for each region

Table 3.

Toxoplasma seroprevalence among blood donors by gender, below and over 40 years, and region, France, 2019 (n = 1,995)

Regions	Males < 40 years (%)	Females < 40 years (%)	p-valuea	Males ≥ 40 years (%)	Females ≥ 40 years (%)	p-valuea
Auvergne-Rhône-Alpes (N = 258)	30.4	22.9	0.554	48.7	58.0	0.301
Bourgogne-Franche-Comté (N = 177)	37.5	21.2	0.242	64.5	56.0	0.470
Bretagne (N = 83)	27.8	12.5	0.500	64.0	75.0	0.600
Centre-Val de Loire (N = 123)	36.4	22.7	0.509	68.3	63.2	0.808
Corse (N = 38)	28.6	42.9	1.000	81.8	69.2	0.813
Grand Est (N = 227)	25.0	6.3	0.027	54.3	64.6	0.296
Hauts-de-France (N = 94)	22.7	47.4	0.184	89.3	56.0	0.015
Ile-de-France (N = 154)	37.5	20.6	0.213	79.5	70.5	0.460
Normandie (N = 91)	31.6	22.7	0.776	81.5	60.9	0.193
Nouvelle-Aquitaine (N = 252)	27.7	20.8	0.591	74.7	78.2	0.740
Occitanie (N = 267)	28.8	32.1	0.883	74.7	66.3	0.317
Pays de la Loire (N = 108)	40.0	14.3	0.132	66.7	67.6	1.000
Provence-Alpes-Côte d'Azur (N = 123)	20.8	29.2	0.739	63.2	67.6	0.874

^aChi-squared test

A multivariable analysis was further performed to confirm the differences of seroprevalences according to sex, age and region. As expected, the risk to be infected by T. gondii increased with age, with odds ratio rising from 2.278 in the 30–39 age group to 36.135 in the group > 70 (p < 0.001), compared to the youngest group (Table 4). Interestingly, it showed that men seemed to be more likely infected by T. gondii (OR = 1.234; 95%CI = [1.014;1.503]; p = 0.036) than women. Five regions out of 12 were associated with an at least twice higher risk of being seropositive, compared to the region with the lowest prevalence (Grand-Est), namely Corse (OR = 2.449), Hauts-de-France (OR = 2.453), Île-de-France (OR = 2.179).

Table 4.

Multivariate logistic regression analysis of factors associated with Toxoplasma seroprevalence among blood donors, France, 2019 (n = 1,995)

Variable	Category	OR	95% CI	p-value
Sex	Male vs Female (Ref.)	1.234	1.014–1.503	0.036
Age	18–29	Ref	Ref	Ref
	30–39	2.278	1.636–3.171	< 0.001
	40–49	5.236	3.789–7.236	< 0.001
	50–59	9.447	6.744–13.234	< 0.001
	60–69	13.199	9.296–18.741	< 0.001
	> 70	36.135	17.789–73.403	< 0.001
Region	Auvergne – Rhône-Alpes	1.090	0.731–1.626	0.672
	Bourgogne – Franche-Comté	1.355	0.873–2.105	0.176
	Bretagne	1.515	0.862–2.663	0.149
	Centre-Val de Loire	1.713	1.046–2.805	0.032
	Corse	2.449	1.129–5.313	0.023
	Grand-Est	Ref	Ref	Ref
	Hauts-de-France	2.453	1.421–4.236	0.001
	Île-de-France	2.179	1.373–3.460	< 0.001
	Normandie	2.039	1.180–3.525	0.011
	Nouvelle-Aquitaine	2.030	1.353–3.044	< 0.001
	Occitanie	1.922	1.290–2.865	0.001
	Pays de la Loire	1.577	0.943–2.636	0.082
	Provence-Alpes-Côte d’Azur	1.471	0.900–2.405	0.124

OR Odds ratio; CI Confidence interval

Discussion

This study is the first one investigating Toxoplasma seroprevalence among a large cohort of French blood donors nationwide. To date, only data from pregnant women are available. The exclusion of blood samples from overseas departments (Réunion, Mayotte, Martinique, Guadeloupe, French Guiana) was decided because of shipping constraints and possible sample alteration. Variation of the number of samples per region (38 to 267) reflects regional population size, as the lowest and highest sample size came from Corse (340,440 inhabitants) and Occitanie (5,933,185 inhabitants). The number of tested sera was the highest ever analysed in this context, which ensures reliable conclusions. Additionally, chance did things well, as the sex ratio of the blood donor population was around 1 for all age categories, which allowed for the first time to compare seroprevalence in male and female. In univariate analysis, a significantly higher prevalence was observed in men aged [30–39] years old (p = 0.033). This age group corresponds to the average age of 31 years for pregnancies in France, with 95% of first births occurring among mothers aged between 21 and 38 (INSEE data for 2023) [11]. The policy of prevention and monthly screening for toxoplasmosis implemented in France since 1992 could account for a better awareness of women regarding toxoplasmosis, and might result in more vigilance about food and hygiene to avoid primary toxoplasmosis. Although these hypotheses were not tested in this study, they might explain the difference in seroprevalences between men and women aged between 30 and 39. Further testing on an even larger sample size would help to confirm these findings. Of note, the mean seroprevalence observed in our study in women of childbearing age (18–39 years) was 22.5% (89/395, Table 1), which is very close to the most recent nationwide seroprevalence study of toxoplasmosis in pregnant women (24.9% in mainland France) [10]. Besides, the mean seroprevalence among blood donors aged > 40 years (66.7%) was similar to that observed among deceased organ donors (68%) in our lab, over a 10-year period (mean age = 61) (data not shown).

The high overall seroprevalence of 50.9% in French blood donors in our study is an important finding, as it shows that the prevalence is still high in the French population whose mean age is 42.7 years (https://www.insee.fr/fr/statistiques/2381476?utm), which is similar to the mean age of our blood donor population (44.8). Here, the seroprevalence in subjects aged > 40 years ranged from 54 to 88%. It is well known that seroprevalence increases with age [6, 12, 13], and older age groups are more exposed to the occurrence of various diseases leading to therapeutic immune suppression, a situation where reactivation of chronic toxoplasmosis remains a major threat [14].

As already described in the study by Mazzili et al. (2025), the highest seroprevalences in our study were observed in Île-de-France and Southern regions, and the lowest in Eastern region [10]. Even though regional comparison is exploratory, as no adjustment or weighting was applied based on regional population size, these differences in prevalence among regions that are sometimes close to each other could be explained by several factors. Firstly by geoclimactic factors, as it was reported that Toxoplasma seroprevalence was higher in regions with high average temperature (Southern regions), and lower in regions with temperatures falling below −5 °C in winter (Eastern regions). This explanation is in relation to better survival and sporulation of Toxoplasma oocysts in warmer environments [8]. Secondly, dietary factors can also account for seroprevalence variation, especially the consumption of sheep meat. Sheep is a mammal with a Toxoplasma prevalence varying among French regions from around 30% (Eastern France) to 72% (South West France) [8]. A correlation between regions where this meat is commonly eaten, i.e. Southern, Northern and Paris regions, and Toxoplasma prevalence among pregnant women has also been pointed out [8, 15]. Berger et al. hypothesized that the supply of sheep meat from countries with low endemicity, such as the United Kingdom and New Zealand, has probably contributed to the decline in the prevalence of toxoplasmosis throughout the years, together with the increasing practice of freezing meat, which destroys Toxoplasma cysts [8]. Finally, many people originating from overseas territories or African countries where toxoplasmosis is highly prevalent, are living in Île-de-France and Southern regions, thus could contribute to the overall higher seroprevalence observed in these regions.

The overall seroprevalence of T. gondii in the present study appears to be higher than those reported among blood donors in other European countries like Portugal (38.1%) [16] or Scotland (13.2%) [12], but seems to be similar to those reported in Romania (45.9%) [13] and Germany (55%) [17]. In other continents, blood donors were reported with seroprevalence ranging from 5.3% in China [18], 9.3% in Taiwan [19], 11.2% in Egypt [20], 16.8–19.3% in Iran [21, 22], 38.5% in Colombia [23], 42.9% in New Zealand [24], 44.4% in Tunisia [25], to 45.3–48% in Brazil [26, 27] (Table 5). These differences could be explained by socio-cultural factors such as diet or socio-economic status [28], or by climate factors and prevalence of Toxoplasma in wildlife, which is higher in the Amazonian forest [29]. However, some studies suffer from a poor demographic representativity or a low number of included blood donors. Indeed, some studies favoured male (Egypt, Iran) or female (New Zealand) recruitment, and others only reported on a small portion of the country population with limited geographical recruitment (China, Brazil, Colombia, Iran, New Zealand) (Table 5). Only two studies conducted in Taiwan and Germany were nationwide, as is our study. Noteworthy, our study is particularly robust, as it does not favour one gender over the other (sex ratio = 1) and it displays a representative fraction of the population of each region.

Table 5.

Comparison of studies on Toxoplasma gondii seroprevalence among blood donors around the world

Country, Year	Sample size	Sex Ratio M/F	Location	Anti-Toxoplasma IgG prevalence (%)	Age (year)	Reference
France, 2024	1,995	1.0	Nationwide France	50.9	18–71	Our Study
China, 2025	702	1.1	Zhejiang Province	5.27	18–59	[18]
Egypt, 2024	420	34	Menoufia Province	11.2	17–66	[20]
Brazil, 2024	1,729	ND	São Paulo state	48	ND	[26]
Brazil, 2022	510	1.1	Erechim and Chapeco (Southern Brazil)	45.3	< 29–69	[27]
Romania, 2022	1,347	1.3	Western Romania	45.9	18–63	[13]
Tunisia, 2020	800	3.9	Gafsa and Monastir	44.4	18–62	[25]
Portugal, 2020	520	0.94	Various	38.1	18–65	[16]
Colombia, 2019	348	2.45	Cucuta	38.5	18–56	[23]
Scotland, 2016	1,403	0.85	Not specified	13.2	17–91	[12]
Iran, 2018	285	30.3	Boyer-Ahmad county	16.8	28–46	[22]
Germany, 2014	6,564	0.91	Nationwide	55	18–79	[17]
Iran, 2014	1,480	16	Fars province	19.3	20–68	[21]
Taiwan, 2012	1,783	1.7	Nationwide	9.3	18–65	[19]
New Zealand, 2007	140	0.59	Waikato Region	42.9	17–69	[24]

M Male; F Female; ND No data

The observation of four blood donors with IgG avidity < 0.200 and positive IgM, raises the question of the risk of parasite transmission through blood transfusion. The presence of high levels of anti-Toxoplasma IgG in all four donors indicates that the primary infection occurred more than a month prior to sampling. Indeed, IgG antibodies are usually detected approximately three weeks after primary infection and increase until they reach a plateau, i.e. two to three months after infection [1]. More than one month after infection, there are no longer any circulating tachyzoites, and therefore no risk of transmission to a transfused patient [1, 30]. We can then assume that none of the donors were at risk of transmitting T. gondii at the time of blood donation. Additionally, it is generally considered that the storage procedure of blood products limits considerably the survival of tachyzoites, which are fragile.

Our study has some limitations, as it was conducted over a short period of time (6 months), but it included a high number of samples and was exhaustive over the study period. It would be of interest to perform similar studies in overseas departments or territories (Tahiti, Wallis and Futuna, Saint-Pierre et Miquelon, French Guyana and French West Indies), as geoclimatic conditions and felid densities and diversity are very different from mainland. As blood donors are selected through eligibility criteria (e.g. exclusion of comorbidities, risk behaviours etc.), it could introduce a selection bias. Toxoplasma seroprevalence in people who are unfit to donate blood for health reasons or due to risky behaviour might differ from our findings obtained on a healthy population.

In conclusion, Toxoplasma seroprevalence in the general population is still high in France, despite a decrease in younger age groups, particularly in women of childbearing age. However, the possibility of infection is still present, as shown by the increasing seroprevalence with age.

Supplementary Information

Below is the link to the electronic supplementary material.

Authors’ Contribution

Conceptualization: JPG, FRG; Investigation: LH; Methodology: FRG; Formal analysis: LH, AB, FRG; Supervision: FRG; Writing original draft: LH; Review & editing: FRG, JPG, AB. All authors read and approved the final manuscript.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data Availability

All data analyzed during this study have been shared on Zenodo, on open repository, and can be retrieved as a raw data set using this link: 10.5281/zenodo.18330122

Declarations

Ethics Approval

Blood donations are made voluntarily to the EFS, and donors give their consent for their use, including serological testing. The study adhered to the Declaration of Helsinki. Samples are anonymized and only a few data remain associated to the sample. Additionally, the study was approved by the ethics committee of the University Hospital of Rennes (approval number #25.153), which waived the necessity to inform donors of the reuse of their blood for secondary study, in relation to the strictly anonymized process and to French regulation (article L. 1211–2 du Code de la Santé Publique).

Consent for Publication

Not applicable.

Use of Artificial Intelligent Tools

None to declare.

Competing interests

The authors declare no competing interests.