Smitha, a resident of Attingal, was proactive in her health by completing a full course of anti-rabies vaccination after being bitten by a stray dog six months ago. However, when she experienced another dog bite a few weeks ago, her doctors recommended just a booster dose instead of another full vaccination course. They warned her that receiving two full courses in quick succession could lead to hyperimmune reactions. Yet, Smitha remained unconvinced, fearing reports of rabies cases in vaccinated individuals, and insisted on undergoing the full vaccination process once more.
Dr. E. Sreekumar, Director of the Institute of Advanced Virology, suggested that Smitha submit a blood sample to assess her immunity levels post-vaccination. Seroconversion refers to the development of specific antibodies in response to infection or vaccination. The World Health Organization stipulates that a rabies virus-neutralizing antibody titre of 0.5 IU/mL or above indicates adequate immune response. The results of Smitha’s blood test revealed an antibody titre of 16 IU/mL, confirming that she did not require another full vaccination.
Effective rabies vaccination relies on inducing a strong neutralizing antibody response against glycoprotein G, a critical viral component. These antibodies prevent rabies by blocking the virus from entering host cells. Traditionally, tests like the Rapid Fluorescent Focus Inhibition Test (RFFIT) and the Fluorescent Antibody Virus Neutralization Test (FAVN) have been used to measure these neutralizing antibodies. However, both require stringent biosafety measures due to their use of live rabies virus, posing challenges in terms of accessibility and cost.
Recently, the Institute of Advanced Virology introduced a simpler assay that employs pseudoviruses for evaluating immune responses in vaccinated humans and animals. Unlike live viruses, pseudoviruses are safer to handle in laboratory environments due to their restricted infectivity. This new vesicular stomatitis virus (VSV)-based assay has shown comparable results to RFFIT when assessing immunity following rabies vaccination.
Dr. Sreekumar underscored the limitations of traditional assays for large-scale use, noting issues related to bio-containment and high costs. The newly developed assay allows for high-throughput analysis, making it particularly useful in rabies-endemic areas. Last year, three cases of rabies in vaccinated children in the State raised concerns about the efficacy of rabies vaccination, highlighting the need for reliable tracking of antibody levels.
The IAV’s assay will serve as a critical tool to ensure that individuals, especially those in high-risk occupations like animal handlers, veterinarians, and forest officials, possess protective levels of antibodies against rabies. Dr. Sreekumar cautioned that many people dismiss pet bites, mistakenly believing their pets are fully protected by their vaccinations. However, without proper cold chain maintenance during storage and transport, the effectiveness of veterinary vaccines can be compromised.
The IAV is dedicated to enhancing public health access to anti-rabies antibody testing for effective immunization monitoring and contributes to the global effort to control and eliminate rabies. This essential test is now available to the public at a cost of ₹500 per sample.
Original Source: https://www.thehindu.com/news/national/kerala/iav-develops-tests-for-checking-the-efficacy-of-anti-rabies-vaccination/article70311023.ece
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Publish Date: 2025-11-22 18:35:00
