This was a multicenter, retrospective, descriptive, and analytical study with a period ranging fron the date of the start of vaccination in Senegal (February 23, 2021) to the end of August 2022 in 4 peritoneal dialysis units in Senegal.

We included all patients in PD for at least 3 months in Senegal.

Patients whose files were incomplete or who refused to answer the questionnaire were not included.

Data were collected on a pre-established form. The survey form recorded the reasons for vaccination, the type and dose of vaccine, and any reasons for non-vaccination.

In our study, patients were considered to have had COVID-19 only when the diagnosis was made biologically by a positive RT-PCR (reverse-transcriptase polymerase chain reaction) or a positive antigenic test.

In addition, severity criteria from the Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia (Trial Version 7) were used. COVID-19 was considered mild when it was asymptomatic (no clinical signs) or only slightly symptomatic (asthenia). It was considered moderate when pulmonary clinical signs and fever were present but did not require hospitalization. Finally, it was considered severe in the presence of respiratory distress with tachypnea greater than 30 cycles per minute or oxygen saturation (SaO2) below 93%, requiring hospitalization in an intensive care unit [5].

Data were entered online on a Google Docs form and then exported to Microsoft Excel 2016. Data analysis was carried out using IBM SPSS (Statistical Package for the Social Sciences) 25. They were expressed using measures of central tendency and dispersion (mean ± standard deviation) for quantitative variables and frequencies for qualitative variables. To compare frequencies, we used Pearson’s chi-square test. Means were compared using the analysis of variance test. A p-value of less than 0.05 was considered significant.

The study protocol was submitted to the National Health Research Ethics Committee at the Ministry of Health and Social Action under reference SEN2022/110.

Of a total of 74 PD patients in Senegal, 49 were included in our study. The mean age of the patients was 43.7 ± 17.5 years. There were 24 men (49%) and 25 women (51%), giving a sex ratio of 0.96. The most frequent nephropathy was benign nephroangiosclerosis (NAS) in 32.7% of cases, followed by chronic glomerulonephritis (CGN) in 24.5%. In the remaining 32.7% of cases, the causative nephropathy was undetermined. The average length of time patients had been in PD was 18 ± 22.2 months. The majority of patients (81.7%) had been in PD for less than 18 months (Table I).

Thirty patients (61.2%) were vaccinated against SARS-CoV2, while 19 patients (38.8%) were not.

In 42% of cases of vaccine refusal, the reason for non-vaccination was both fear of vaccine side effects and minimization of the severity of COVID-19. Six patients (31.6%) refused the vaccine solely out of fear of side effects, and 5 patients (26.3%) refused the vaccine only because COVID-19 did not seem serious enough to warrant vaccination.

All vaccinated patients (30) were vaccinated to protect themselves, and 27 patients (90%) were vaccinated to protect those around them. No patient was vaccinated because of an external obligation (international travel, obligation to be vaccinated in the workplace or for access to certain public places, etc.).

Twenty-five patients (83%) had received 2 doses of vaccine (15 with AstraZeneca and 10 with Sinopharm), while the remaining 5 patients (17%) had received a single dose (4 with AstraZeneca and 1 with Johnson & Johnson). No patient had received 3 doses.

Nineteen patients (63.3%) had received the ChAdOx1 nCoV-19 vaccine (AstraZeneca), 10 patients (33.3%) had received the BBIBP-CorV vaccine (Sinopharm), and 1 patient had received the JCOVDEN vaccine (Johnson & Johnson).

Sixteen vaccinated patients (53%) experienced side effects after vaccination.

All patients experiencing side effects (16) had pain at the inoculation site, and 4 (25%) had flu-like symptoms.

Two patients (7% of those vaccinated) contracted COVID-19 after vaccination, including one with a severe form 3 months after vaccination. Both these patients were vaccinated with the Sinopharm vaccine.

Factors associated with non-vaccination

Vaccinated patients were older than unvaccinated patients, with an average age of 47.6 versus 37.6 years. This difference was statistically significant, with a p-value of 0.048 (Table II).

Vaccinated patients accounted for 61.2% of cases. In the general population, only 8.7% of Senegalese had received 1 dose of SARS-CoV2 vaccine, and 6.4% had received 2 doses [2]. The higher vaccination coverage of PD patients compared with the general population may be related to the prioritization of chronically ill patients during the first phase of the vaccination campaign, but also to the important work carried out by nephrology and PD teams to raise patients’ awareness of the fact that End-stage renal disease constitutes a high-risk terrain for progression to severe forms of COVID-19. In Togo, Tsevi et al. reported that only 50% of hemodialysis patients were vaccinated against SARS-CoV2 [6]. In France, Bensouna et al. reported a much higher vaccination coverage of 96.7%, compared with 80.9% for the general population [2][7].

In the United States, Garcia reported vaccination coverage of 80% in a population of hemodialysis patients [8]. In Africa, the low vaccination coverage of renal replacement therapy (RRT) patients, and more generally of the general population, can be explained by the proliferation of “conspiracy theories” and “fake news” on social networks calling into question the efficacy and safety of vaccines and even the actual existence of COVID-19. This mistrust has been further exacerbated by the low apparent impact of COVID-19 on the African continent compared with the rest of the world [9].

Fear of long-term vaccine side effects and minimization of the seriousness of COVID-19 were both reasons for vaccine refusal in 42% of our patients. In Togo, a study of a population of chronic hemodialysis patients reported fear of vaccine side effects in 51.2% of patients, doubts about vaccine quality in 49.6%, and doubts about vaccine efficacy in 33.3% of cases [6]. A study by Blanchi et al. conducted in several hemodialysis centers in France and Italy found that doubts about efficacy and fear of side effects were the main reasons for vaccine refusal. On the other hand, a relationship of trust between nephrologist and patient was correlated with acceptance of vaccination [10].

Furthermore, Andrian reported in a study of hemodialysis patients in France that 90% of unvaccinated patients were not convinced of the vaccine’s efficacy, and 84% had doubts about the vaccine’s quality and possible long-term side effects [11].

This lack of confidence may be related to the vaccine manufacturing process, such as rapid development that does not allow sufficient hindsight and formal proof of safety, the development of new vaccine processes such as RNA vaccines that have generated fears among patients, and also the lack of transparency in vaccine development and during clinical trials [12][13].

On the other hand, populations may have had concerns about being used as guinea pigs, as was the case for the tenofovir trials on populations at risk of contracting HIV, or more recently in 2015 in Ghana for the Ebola vaccine [14][15].

All vaccinated patients were vaccinated to protect themselves, and 90% were vaccinated to protect those around them as well as themselves.

A Togolese study of hemodialysis patients found similar reasons to our study. Indeed, 90.9% of patients were vaccinated to protect against severe forms of COVID-19, 54.5% because of their advanced age, and 43.2% because of their comorbidities [6]. In France, where much higher vaccination coverage (96.7%) is reported, the reasons for vaccination were not included in the study, but this could be explained by the fact that a health pass was often required in many situations, unlike in Senegal, where it has always been voluntary [7],[16],[17].

In our study, no patient had received a complete 3-dose vaccination schedule. A majority (83%) had received 2 doses, and the remaining 17% a single dose.

In the various studies carried out in the West and in China, all vaccinated patients had received a complete vaccination schedule, i.e., 3 doses, or 2 doses if the Johnson & Johnson vaccine was used [6][8][15] .

This can be explained by the rush for vaccines in Senegal only at the start of the campaign and the growing lack of interest in vaccination among the population, given the much lower impact and mortality of COVID-19 in Africa.

Sixty-three percent of patients were vaccinated with AstraZeneca’s vaccine, 33.3% with Sinopharm’s, and only 1 patient with Johnson & Johnson’s vaccine. No patient was vaccinated with an mRNA vaccine. In the West, in all studies found, dialysis patients were vaccinated with mRNA vaccines (Pfizer-BioNTech),[7][18][19][20]. This may be explained by the fact that, in Senegal, vaccination was reserved primarily for patients with chronic diseases, and dialysis patients in particular. At the start of the vaccination campaign, only vaccines from AstraZeneca and Sinopharm were available. These vaccines were chosen not only for their availability, but also for their accessible method of storage (in a refrigerator between 2 and 8°C), unlike the Pfizer-BioNTech vaccine, which requires a freezer to ensure a temperature below -15°C [4]. Furthermore, the predominant use of mRNA vaccines in the West was due to a better humoral response in dialysis patients, as reported by Chen and Grupper, leading them to be recommended as first-line vaccines for dialysis patients [21][22].

Fifty-three percent of patients experienced side effects after vaccination, such as pain at the inoculation site in 100% of cases, flu-like symptoms in 25%, and diarrhea in 6.3%. In Seck’s study, 81.5% of patients reported no adverse effects. Of the 18.5% who did experience adverse reactions, 6.2% reported flu-like symptoms, 6.2% localized myositis, and 3.7% diarrhea [23]. A study by Zitt et al. in Austria found pain at the inoculation site in 38% of cases, diarrhea in 8%, and asthenia in 8% [24].

The disparity in results between our study and the literature can be explained by the different vaccines used in the studies. Indeed, patients in our study were vaccinated using 3 different vaccines (AstraZeneca, Sinopharm, and Johnson & Johnson), whereas in Seck’s study, patients used only the AstraZeneca vaccine, and those in Zitt et al.’s study only the Pfizer-BioNTech vaccine. Given the multitude of vaccines used in our study, it is difficult to establish an adverse event profile for each vaccine.

Only 6.7% of vaccinated patients tested positive for SARS-CoV2 after vaccination. These results are in line with various studies carried out in dialysis patients, which have shown that not only was their vaccine response diminished, but also that protective antibody levels fell more rapidly than in the general population, currently justifying the need for a second booster dose 3 months after the first booster (i.e., 4 injections in total) [25][26].

The authors declare no conflict of interest for this article.