Rabies viral RNA and antibody response after post-exposure prophylaxis: Implications for blood donor deferral

Abstract

Background

Rabies post-exposure prophylaxis (PEP) using anti-rabies vaccine and immunoglobulin is widely recognized as highly effective. However, individuals who receive PEP are typically deferred from blood donation for a full year, largely due to theoretical concerns about transfusion safety. However, the evidence supporting such a prolonged deferral remains limited.

Objectives

This study aimed to assess rabies real-time RT-PCR status and serological responses among PEP recipients at various intervals following treatment and to consider whether these findings might justify a re-examination of the current one-year blood donor deferral policy after anti-rabies treatment.

Methods

We conducted a single-center interventional study at an anti-rabies clinic in a tertiary hospital in North India. The study enrolled twenty immunologically naïve adults who had sustained category III animal bites, with no prior rabies exposure or treatment, and who adhered fully to the protocol. Participants received anti-rabies vaccines and equine rabies immunoglobulin as appropriate for their category. Follow-up samples were collected between as early as 48 days and 120 days after the bites. These samples were tested for rabies viral RNA using real-time RT-PCR (Geno-Sens Rabies Real-Time PCR Kit), and antibody titers were measured using ELISA (Rabies Platelia Kit II). Data analysis included descriptive statistics, percentile analysis, correlation analysis, and regression analysis, as appropriate.

Results

In this cohort, dogs were responsible for 90% of bites, with 85% of incidents being unprovoked and 65% involving lower limbs. All participants tested negative using RT-PCR. ELISA titers ranged from 0.881 to 4.449 IU/mL, and all participants exceeded the protective threshold of 0.5 IU/mL. The mean titer was 2.97 ± 1.04 IU/mL.

Conclusion

The lack of detectable rabies viral RNA, together with sustained protective antibody titers, indicates an effective response to PEP in this group. These findings support a more evidence-based reconsideration of the current prolonged blood donor deferral following anti-rabies treatment.

Author summary

Rabies remains a major public health concern in India, where most human exposures occur after animal bites, especially dog bites. Post-exposure prophylaxis using anti-rabies vaccine and rabies immunoglobulin is highly effective when given correctly. However, people who receive anti-rabies treatment are often deferred from blood donation for one year, mainly because of theoretical concerns about transfusion safety. Evidence supporting such a long deferral period is limited. In this study, we followed 20 immunologically naïve adults with category III animal bites who received standard anti-rabies post-exposure prophylaxis. Blood samples were collected 48 to 120 days after exposure and tested for rabies viral RNA using real-time RT-PCR and for rabies antibody levels using ELISA. All participants were RT-PCR negative, indicating no detectable rabies viral RNA. All also had antibody levels above the accepted protective threshold. These findings suggest that individuals who complete appropriate anti-rabies post-exposure prophylaxis may not have detectable circulating viral RNA and maintain protective antibody responses during follow-up. Larger multicenter studies are needed, but these results support reconsideration of the current one-year blood donor deferral. Our findings suggest the potential for shortening the current one-year deferral for PEP recipients, supporting evidence-based transfusion policies after anti-rabies treatment.

Introduction

Rabies remains a significant public health challenge in India, primarily because of its transmission through dog bites. It causes high mortality, with India alone accounting for approximately 20,800 human rabies deaths annually — over 35% of the global burden of ~ 59,000 deaths. The Indian Million Death Study, a nationally representative verbal-autopsy survey of more than 122,000 deaths, documented 12,700 symptomatically identifiable furious rabies deaths in 2005 (overall mortality rate 1.1 per 100,000; 99% CI 0.9–1.4) and showed that 50% of all rabies deaths in India occur in children below 15 years of age, with a male preponderance (62%) and a marked rural concentration (91%). The pediatric predominance reflects children’s shorter stature, their closer interaction with dogs, and bites that are more often concentrated on the head and face [1–3].

The standard rabies vaccination protocol includes wound cleansing, multiple rabies vaccine doses (intramuscular or intradermal), and human rabies immunoglobulin for category III exposures [4, 5].

The 1-year deferral period for blood donation after receiving an anti-rabies vaccine is primarily to prevent transient false-positive results in blood donor screening, specifically related to vaccine components that may mimic the viral antigens. Current guidelines recommend a temporary deferral period of one year for blood donors who have received postexposure prophylaxis with anti-rabies vaccine (PEP-ARV) after an animal bite. However, limited evidence is available regarding its wider consequences, particularly its effect on the eligible blood donor pool. A 2018 study conducted at one of the largest government hospitals in the national capital reported that 11.02% of blood donors were temporarily deferred because of a recent animal bite or receipt of anti-rabies vaccination. This was among the three leading causes of temporary donor deferral, after low body weight (15.59%) and anemia [6].

RT-PCR is a sensitive and specific method for rabies diagnosis, detecting viral RNA even when antigen levels are low or tissue is degraded. Studies show it complements or outperforms fluorescent antibody and immunohistochemistry tests and enables rapid, reliable detection of lyssaviruses through real-time assays [7, 8].

A negative RT-PCR result in recipients of anti-rabies vaccination following animal bites generally indicates the absence of detectable rabies viral RNA, suggesting effective viral clearance or no active infection. This supports the successful prevention of rabies when post-exposure prophylaxis is properly administered, although clinical vigilance remains essential since rare failures due to host immunocompromise can occur [9].

Previous studies on deferral periods for blood donation after rabies vaccination are limited to a few. However, standard guidelines commonly recommend a temporary deferral of approximately 12 months after rabies vaccination, especially post-exposure, to ensure transfusion safety because of the potential presence of the virus. More broadly, research shows that short-term temporary deferrals, regardless of the cause, significantly reduce donor return rates and subsequent donations, highlighting the need for effective donor communication to mitigate these effects [10, 11].

However, the evidence supporting the duration of blood donor deferral after animal bite and anti-rabies vaccination remains limited. In particular, there is a lack of data on whether individuals who have received post-exposure prophylaxis demonstrate detectable rabies viral RNA or inadequate rabies-specific antibody response during the deferral period. This gap is important because current deferral practices may affect donor availability in rabies-endemic settings, yet their laboratory and immunological basis has not been adequately evaluated.

Therefore, we conducted a single-center study to assess the status of RTPCR in recipients of anti-rabies treatment (ARV and RIG) at different time points after post-exposure prophylaxis and to re-evaluate the 1-year deferral for blood donation based on these results.

Objectives

Primary

To assess the RT-PCR and ELISA antibody status of individuals who received anti-rabies post-exposure prophylaxis, including anti-rabies vaccine and rabies immunoglobulin, at different time intervals (Day 0,14,28 and Dx) after treatment, in order to re-evaluate the current one-year blood donation deferral period following anti-rabies vaccination.

Secondary

To assess the proportion of anti-rabies post-exposure prophylaxis recipients who remained RT-PCR negative at different time intervals after Completion of Anti-Rabies Treatment.

To evaluate the earliest post-treatment interval at which RT-PCR negativity may support safe reconsideration of blood donation eligibility.

To determine rabies virus-specific antibody titres using ELISA and to analyse their relationship with animal bite exposure and/or receipt of post-exposure prophylaxis.

Methodology

Study type

Longitudinal, single-center, observational study.

Study area

An anti-rabies clinic in a tertiary care hospital in Northern India.

Sample size

The study included twenty participants, selected by convenience in accordance with the available budget. This pragmatic approach to sample size is recognized as a limitation, particularly in the interpretation of the statistical significance of the findings.

A post hoc assessment was performed to contextualize statistical precision.

With a sample size of 20, the study provided adequate statistical precision for estimating mean antibody titres, with the observed mean (2.97 IU/mL) yielding a 95% confidence interval (2.514–3.426 IU/mL), which remained substantially above the WHO protective threshold of 0.5 IU/mL, supporting robust seroconversion in this cohort. For RT-PCR, the absence of positive cases corresponds to an upper 95% confidence limit of approximately 15% using the “rule of three,” indicating that rare positivity cannot be excluded despite zero detection. However, the study was underpowered for correlational analyses (estimated power ~ 22%), and therefore non-significant associations should be interpreted cautiously as exploratory findings rather than evidence of absence of effect.

Enrolment criteria

All category 3 animal bite patients above the age of 18 years with no previous history of exposure or treatment, willing to provide informed consent, and available for follow-up were included. Referred cases from other centers for immunoglobulin, participants with immunodeficiency (Cancer, HIV, HCV, TB, etc.), and those not willing to provide informed consent were excluded.

Ethical clearance

The study was approved by the Institutional Ethics Committee, Government Medical College, Patiala, Punjab, NECRBHR, DHR Reg.No.EC/NEW/INST/2023/PB/0383vide letter no.9(310)2026/15,045. Dated 10/04/26.

The present sample of patients were part of an earlier Clinical trial with Ethical Clearance dated 24/07/2024 Clinical Trial registered vide CTRI number - CTRI/2024/07/071408 which was registered on 26/07/2024 and study completed in February 2026.

Subsequent new Ethical approval was taken for present study as per Institutional Ethical Guidelines that any change in study criteria or use of same patient pool must be vide new Ethical Approval with study commencing in Second week of April 2026 post Ethical Approval.

Compliance

As per a pre-designed protocol prospectively developed and internally approved by experts in the field of rabies at a departmental meeting, a deviation of ± 2 days was allowed regarding vaccination schedule compliance, and subsequent doses were adjusted accordingly.

The protocol was not independently preregistered.

Antibody and RT-PCR testing were performed at the Research Lab of the Department of Virology, Government Medical College, Amritsar, which is a Center of Excellence in Punjab under the National Rabies Control Program. Antibody testing was performed using the ELISA method, free of cost, using the RABIES PLATELIA KIT II. PCR testing was done using Geno-Sens Rabies Real-Time PCR Kit.

The Rabies PLATELIA KIT II is an enzyme-linked immunosorbent assay (ELISA) used to detect rabies antibodies in serum or other body fluids. Known for its high sensitivity and specificity, it is a reliable diagnostic tool in both humans and animals. This kit is widely used in PEP to assess immunity and vaccine efficacy. Its advantages include rapid results, ease of use, and compatibility with diverse laboratory setups, ensuring accurate rabies diagnosis. A titer of ≥ 0.5 International units (IU)/ml (or Equivalency units (EU)/ml equivalent in ELISA) is widely accepted as protective seroconversion per WHO/OIE guidelines and rabies serology interpretations [12].

ELISA testing was performed at Day 0, Day 14, Day 28, and Dx.

RT-PCR was performed using the Geno-Sens Rabies Real-Time PCR Kit, according to the manufacturer’s instructions only once on Dx.

The Geno-Sens Rabies Real-Time PCR Kit is a qualitative molecular diagnostic assay for the detection of rabies virus RNA using reverse-transcription real-time polymerase chain reaction. After RNA extraction, viral RNA was converted into complementary DNA and amplified using rabies virus–specific primers and probes. The major advantages of this kit include a rapid turnaround time, closed-tube amplification, reduced contamination risk, high analytical sensitivity for low-copy viral RNA, and improved specificity enabled by probe-based target detection. In rabies diagnosis, real-time RT-PCR is considered useful because it can detect viral nucleic acid even when antigen levels are low, and it provides objective molecular confirmation [13, 14].

Biologicals used

All biologicals used were available free of cost under government supply.

Anti-rabies vaccine

CHIRORAB manufactured by Chiron Behring, which is a Purified Chick Embryo Cell Vaccine (PCEC) with batch number R25047D.

Anti-rabies serum

Premi-RAB, manufactured by Premium Serum and Vaccines Private Limited, with batch number RAB-091, is an EQUINE IMMUNOGLOBULIN.

RT-PCR sample and ELISA was collected post completion of treatment on Dx and ELISA was also done on varying intervals at Day 0,14 and 28.

Data collection/analysis

Data were collected using a pretested semi-structured questionnaire that included sociodemographic, animal-bite, and treatment/intervention details. The collected data were cleaned and entered into Microsoft Excel (2021) for further analyses. The results are reported as frequencies, percentages, means with standard deviations, percentile distributions, correlation coefficients, regression estimates, and visual models. The primary statistical methods included descriptive frequency analysis, percentile analysis, Pearson and Spearman correlations, simple linear regression. The Statistical software used was SPSS Trial version 26.

Ethical compliance

All procedures performed in the study involving human participants were in accordance with the ethical standards of the Institutional Ethics Committee and the 1968 Helsinki Declaration and its later amendments, or with comparable ethical standards.

Clinical trial statement

Not applicable as present manuscript is a secondary analysis of another previously registered study.

The study schema is presented in Fig. 1.

Fig. 1.

Study schema

Results

All participants adhered to the protocol established prior to the study, and all were seronegative at baseline, confirming their immunological naïveté.

The study cohort comprised 20 participants, all of whom received anti-rabies post-exposure prophylaxis and underwent both RT-PCR and ELISA antibody titer assessments.

Table 1. Socio-demographic and bite characteristics.

Table 1.

Baseline characteristics of the study participants

VARIABLE	CATEGORY	NO. OF PATIENTS
AGE GROUP	18–30 YEARS	10
AGE GROUP	31–45 YEARS	6
AGE GROUP	46–60 YEARS	4
SEX	MALE	14
SEX	FEMALE	6
PLACE OF RESIDENCE	URBAN	12
PLACE OF RESIDENCE	RURAL	8
MONTHLY INCOME	CLASS 1	17
MONTHLY INCOME	CLASS 2	2
MONTHLY INCOME	CLASS 3	1
BITING ANIMAL	DOG	18
BITING ANIMAL	CAT	1
BITING ANIMAL	OTHERS	1
NATURE OF BITE	UNPROVOKED	17
NATURE OF BITE	PROVOKED	3
SITE OF BITE	LOWER LIMBS	13
SITE OF BITE	UPPER LIMBS	7

Frequency and percentage analyses revealed that 10/20 participants (50%) were aged 18–30 years, 6/20 (30%) were 31–45 years old, and 4/20 (20%) were 46–60 years old. Males accounted for 14/20 (70%) and females for 6/20 (30%) patients. Urban and rural residents comprised 12/20 (60%) and 8/20 (40%), respectively. Income class 1 included 17/20 (85%), class 2 2/20 (10%), and class 3 1/20 (5%).

Dogs were the biting animals in 18/20 cases (90%), whereas cat and other animal bites were reported in 1/20 cases (5% each). Unprovoked bites occurred in 17/20 participants (85%), whereas provoked bites occurred in 3/20 (15%). The lower limb was involved in 13/20 (65%) cases and the upper limb in 7/20 (35%) cases (Table 1).

Analysis at the individual level revealed that samples were collected between 48 and 120 days after the animal bite. All participants (20/20) were RT-PCR-negative, indicating no detectable rabies viral RNA at the time of sampling. ELISA titers ranged from 0.881 to 4.449 IU/mL, and all participants had antibody titers above the protective threshold of 0.5 IU/mL by day 14, suggesting uniform serological protection within the cohort (Table 2).

Table 2.

Raw patient data: RT-PCR and ELISA titre

S. NO	TITRE AT DAY 0(Iu/ml)	TITRE AT DAY 14(Iu/ml)	TITRE AT DAY 28(Iu/ml)	DAYS OF SAMPLE COLLECTION AFTERRABID ANIMAL BITE	RT-PCR STATUS	TITRE on Dx
1	0.013	1.23	1.3	99	NEGATIVE	1.107
2	0.068	1.200	2.576	50	NEGATIVE	2.887
3	0.056	2.831	3.764	48	NEGATIVE	4.082
4	0.009	1.758	3.721	74	NEGATIVE	1.613
5	0.030	5.120	6.123	73	NEGATIVE	4.449
6	0.027	0.780	1.650	96	NEGATIVE	3.912
7	0.045	1.250	2.987	68	NEGATIVE	3.708
8	0.054	2.290	2.449	100	NEGATIVE	3.051
9	0.011	1.887	2.634	89	NEGATIVE	3.978
10	0.025	5.124	5.950	99	NEGATIVE	3.274
11	0.014	3.89	4.307	93	NEGATIVE	2.239
12	0.029	5.020	5.733	120	NEGATIVE	0.881
13	0.03	2.463	3.125	100	NEGATIVE	3.145
14	0.009	1.31	4.786	90	NEGATIVE	4.131
15	0.019	0.649	0.607	90	NEGATIVE	2.983
16	0.026	1.857	3.886	103	NEGATIVE	2.807
17	0.015	0.565	0.615	106	NEGATIVE	2.812
18	0.056	2.831	3.765	59	NEGATIVE	4.002
19	0.040	2.485	3.753	71	NEGATIVE	2.642
20	0.038	1.200	1.645	51	NEGATIVE	1.666

*DX= Varying number of days when the sample was collected after completing post-exposure prophylaxis

Descriptive analysis indicated that the mean duration between the bite and sampling was 83.95 ± 20.82 days, with a range of 48–120 days. The mean ELISA titer was 2.97 ± 1.04 IU/mL, ranging from 0.881 to 4.449 IU/mL. All participants had titers above 0.5 IU/mL, resulting in a uniformly protective antibody response across the groups (Table 3).

Table 3.

Descriptive statistics

Variable	N	Mean	Std Dev	Minimum	Maximum
Days After Bite	20	83.95	20.82	48	120
Titer by ELISA	20	2.97	1.04	0.881	4.449

Percentile analysis was performed to describe the distribution of ELISA antibody titres among participants. The 25th percentile was 2.541 IU/mL, the median was 3.017 IU/mL, the 75th percentile was 3.929 IU/mL, and the 90th percentile was 4.087 IU/mL. These findings indicate that antibody responses were consistently above the WHO protective threshold of 0.5 IU/mL, including among participants at the lower end of the distribution. The percentile analysis was used as a descriptive approach to demonstrate variability and uniformity of immune responses within this small study population (Table 4).

Table 4.

Percentile distribution of ELISA titres

25th Percentile (Q1)	50th Percentile (Median)	75th Percentile (Q3)	90th Percentile
2.541	3.017	3.929	4.087

Pearson and Spearman rank correlations were applied to examine the relationship between the number of days after the bite and ELISA titer. The Pearson correlation was r = − 0.279 (p = 0.234) and the Spearman correlation was ρ = −0.332 (p = 0.153). Both analyses showed a weak negative association, suggesting a mild decline in titer over time, though neither reached statistical significance in this sample of twenty participant (Table 5).

Table 5.

Correlation analysis

Correlation Metric	Coefficient (r)
Pearson (Linear)	-0.279
Spearman (Rank)	-0.332

Correlation and visual data modelling

RT-PCRtiter correlation could not be meaningfully calculated because 20/20 participants (100%) were RT-PCR-negative, leaving no variability in RT-PCR status. Correlation requires variation in both variables.

A scatter plot comparing RT-PCR values with antibody titers showed a horizontal clustering of RT-PCR results at the negative threshold level, whereas antibody titers were distributed across a broad range. This pattern visually shows the absence of direct association between viral RNA detection and antibody concentration (Fig. 2).

Fig. 2.

Scatter plot comparing RT-PCR values with antibody titers

Fig. 3.

Similarly, a scatter plot illustrating temporal trends would show a stable flat line for RT-PCR values, in contrast to fluctuating or progressively rising antibody titer curves. This visualization highlights that antibody dynamics continue despite the absence of detectable viral RNA. Heat maps or box-and-whisker plots may additionally demonstrate titre variability among subjects while reinforcing the uniform negativity of RT-PCR findings (Fig. 3)

Overall, all 20/20 participants (100%) were RT-PCR negative, and all 20/20 (100%) had protective ELISA titers above 0.5 IU/mL. Correlation analysis showed a weak, non-significant negative association between the number of days after the bite and the titer.

Discussion

The demographic profile of our cohort — predominantly young adult males residing in urban and lower-socioeconomic settings, with dogs responsible for 90% (18/20) of bites, 85% (17/20) unprovoked and 65% (13/20) involving the lower limbs — aligns closely with the Institut Pasteur du Cambodge PEP cohort reported by Nisa Ya et al., in which 78 of 148 patients were bitten by laboratory-confirmed RABV-positive dogs and were given the WHO-recommended IPC intradermal PEP regimen alongside equine rabies immunoglobulin (eRIG). Nisa Ya et al. reported that 100% (148/148) of these conformed to the same cat-III / dog-bite profile as our North Indian cohort, including a comparable rural/urban and age distribution. This similarity supports the relevance of our 20-participant cohort for PEP immunogenicity evaluation. The predominance of dog-mediated exposure in our data (90%) is also consistent with the global estimate that dogs account for ≥ 95% of human rabies cases worldwide [14].

Our RT-PCR findings — all 20/20 participants negative on real-time RT-PCR between days 48 and 120 post-bite — concur with the systematic-review evidence assembled by Preiss et al. from 54 estimates of immune response to PCECV-based PEP, which documented that almost all individuals develop RVNA ≥ 0.5 IU/mL by day 14 and clear any viral challenge without detectable viremia during follow-up. Notably, the Preiss et al. meta-analysis identified zero failures among immunocompetent PEP recipients in the 54 evaluated estimates, mirroring our 100% RT-PCR negativity. The Preiss PCECV evidence base also corroborates the safety profile of PCECV-based regimens — the same vaccine class (CHIRORAB, batch R25047D) administered in our study. Active infection or vaccine failure remains exceptionally rare; the only documented PEP failure with a cell-culture-based vaccine in the Western Hemisphere was reported by Holzbauer et al. in 2023, in which previously unrecognized impaired immunity — not vaccine failure per se — was the most plausible explanation for breakthrough infection. As Holzbauer et al. concluded, clinicians should consider measuring rabies neutralizing antibody titers after PEP completion if there is any suspicion of immunocompromise — an approach directly relevant to our exclusion of immunocompromised individuals and our ELISA-based titer verification [9, 13].

Regarding serological responses, our antibody titers (0.881–4.449 IU/mL; mean 2.97 ± 1.04) exceeded the WHO protective threshold of 0.5 IU/mL and align with three evidence streams. In the IPC PEP cohort, Nisa Ya et al. reported 98.6% seroconversion by day 14, 87% protective nAb titers at 12 months, and sustained IL-4 and IFN-γ–secreting T-cell elevations through 1 year, supporting persistence beyond typical RT-PCR clearance follow-up. Preiss et al.’s PCECV systematic review/meta-analysis showed that most of > 54 cohorts achieved protective titers by day 14, matching our 100% day-14 PCECV-class response. Vien et al. found 100% of Vietnamese children receiving low-dose intradermal vaccine maintained RVNA ≥ 0.5 IU/mL for 5 years post-booster, with gradual waning consistent with our non-significant time-since-bite correlations (Pearson r = − 0.279; Spearman ρ=−0.332). Thus, our lower quartile remained 5× protective (Q1 = 2.541), and the 90th percentile reached 4.087 IU/mL. Collectively, these results support durable immune memory and effective anamnestic protection, consistent with De Benedictis et al.’s RVC20/RVC58 cocktail findings: broad lyssavirus neutralization, preserved endogenous antibody responses, hamster protection, and no viral persistence [13–16].

Our full adherence to PEP, supported by Shankaraiah’s Bangalore anti-rabies clinic (n = 735), where 80.4% completed the 5-dose intramuscular Essen regimen with compliance declining from 100% at dose 1 to 80.4% at dose 5, contextualizes interpretation. Our 100% protocol-adherent cohort represents a best-case immunological benchmark, contrasting population-level attrition (~ 20%) that may affect antibody magnitude and durability. RT-PCR negativity and sustained antibody levels support that PEP induces effective viral clearance with durable post-exposure immunity and minimizes subclinical or persistent infection. This aligns with Preiss et al.’s meta-analysis of 54 cohorts where PCECV regimens achieved RVNA ≥ 0.5 IU/mL by day 14, with variability driven by host factors, schedule, and sampling timing rather than ongoing viral presence. Concordant visual data modelling further substantiates response robustness over time [13, 17].

From a clinical and transfusion-safety perspective, our data indicate that patients completing PEP do not harbor active virus and pose no transmission risk, supported by convergent evidence. Tarantola et al.’s 12-year Cambodian retrospective (n = 3,318; 1,739 traced) reported 99.83% survival (95% CI 99.49–99.96%) among PEP-compliant recipients exposed to confirmed rabid dogs, with no deaths attributable to post-PEP viral persistence. Shankaraiah et al. show that only full PEP completion—as in our 100% adherent cohort—achieves the immunological benchmark underpinning safe eligibility reconsideration. Preiss et al.’s PCECV meta-analysis across 54 immune-response estimates found no vaccine-related viremia in compliant recipients, supporting that deferral policies may exceed biological risk. Martín-Dávila et al. document only 8 corneal-transplant cases and 2 solid-organ clusters worldwide, estimating transfusion risk at < 1 in 10¹² even under extreme incidence scenarios, while Lu et al. confirm no confirmed human-to-human transmission except rare transplant events. No transfusion-transmitted rabies has been reported, reinforcing negligible risk in PEP-completed donors [13, 17–20].

Nonetheless, our interpretation should be contextualized within the rare but documented instances of PEP failure. Notably, Holzbauer et al. reported the first PEP failure in the Western Hemisphere using a cell-culture-based vaccine, attributing the breakthrough to previously unrecognized impaired immunity (host-mediated primary vaccine failure) rather than vaccine or protocol failure; the paper recommends post-PEP antibody titer measurement whenever immunocompromise is suspected. Although these exceptions are uncommon, they underscore the need to balance low transmission risk with vigilance in immunologically impaired individuals. Expanding serological monitoring or individualized risk assessment could enhance donor safety without overly restrictive deferral [9].

Conclusion

This study demonstrates that all participants achieved protective antibody titres above the WHO threshold following post-exposure prophylaxis, with no RT-PCR positivity detected, supporting effective prophylaxis. However, the small convenience sample size of 20 limits statistical power and generalisability, making findings exploratory. Borderline serological variability further constrains interpretation. Larger multicenter prospective studies with 200–300 participants per group, predefined longitudinal sampling, and inclusion of high-risk populations such as immunocompromised individuals are required to validate immune kinetics and strengthen clinical and policy relevance.

Specifically, a shortened deferral interval of approximately 3 months post-PEP completion could be explored in future policy evaluations, provided confirmatory evidence from larger multicenter studies. This recommendation is intended as hypothesis-generating and not practice-changing at the current stage.

Strengths and limitations

The strengths of this study include its focused clinical question, enrolment of immunologically naïve category III bite victims, complete protocol compliance, combined molecular and serological assessment, and use of real-time RT-PCR with ELISA antibody titer measurement at clinically relevant follow-up intervals. These findings directly address an important transfusion policy issue with limited evidence.

The limitations of this study include the small convenience sample of 20 participants, single-center design, absence of a control group, and follow-up restricted to 48–120 days. Rare PEP failures, immunocompromised individuals, and early post-treatment viremia cannot be excluded. Therefore, multicenter studies with larger sample sizes and serial repeat testing are required.

Abbreviations

PEP

Post-Exposure Prophylaxis

RT

PCR-Reverse Transcriptase Polymerase Chain Reaction

ELISA

Enzyme-Linked Immunosorbent Assay

ARV

Anti-Rabies Vaccine

RIG

Rabies Immunoglobulin

IU/mL

International Units per Milliliter

WHO

World Health Organization

RNA

Ribonucleic Acid

Dx

Day of sample collection / Days post-exposure (as used in tables)

SD

Standard Deviation

Q1

25th Percentile

Q3

75th Percentile

SPSS

Statistical Package for the Social Sciences

Author contributions

Conceptualization/Study design – ADS, SO, SG. Resources – ADS, KA, SG, SK. Methodology – ADS, SO, SK. Software – ADS, SG, AK, MG. Data analysis- ADS, SO, KA. Investigation- AK, MG, RB. Visualization – ADS, SK, KA. Writing/Original draft-ADS, SO. Writing/Reviewing/Editing-SO, KD. Supervision/Project Administration- ADS, SO, KD.

Funding

The author’s received no financial support for the research, authorship- and/or publication of this article.

Data availability

No datasets were generated or analysed during the current study.

Declarations

AI disclosure

During the preparation of this work, the author(s) used Grammarly/Paper Pal to check the grammar and assist with the literature search. After using these tools/services, the author(s) reviewed and edited the content as needed and took full responsibility for the content of the published paper

Competing interests

The authors declare no competing interests.