'Anti-rabies vaccine is very effective but there are other factors at play'
Rabies remains a formidable public health challenge in India, with around 20,000 annual deaths accounting for 36% of the global toll, according to WHO. In a conversation with
Pushpa Narayan, Dr B Sekar, former director of the Pasteur Institute of India in Coonoor which supplies vaccines to the Centre, explains why some bites are more dangerous than others
Last month, three children died in Kerala even after rabies shots, raising questions about quality. Why are such deaths happening despite vaccinations? Aren’t the vaccines effective?
Anti-rabies vaccines are incredibly effective. But, in some cases, they may fail owing to several factors, including the time of vaccination, dosage, and the type of wound care. For instance, if someone is bitten by a rabid animal and has a category 3 wound, then getting the vaccine right away, along with a rabies immunoglobulin shot, is crucial to make treatment 100% effective in preventing the disease. Also, the person must complete the full vaccination course — day 0, 3, 7, 14, and 28 for most intramuscular route vaccinations and day 0, 3, 7, and 28 for most intradermal vaccinations. Many skip vaccinations if they see the wound heal or if they don’t see visible wounds, both of which are wrong.
What is a category 3 wound? Why is it so serious?
Doctors classify wounds into categories to determine appropriate post-exposure treatment for rabies. Category 3 is considered the most severe type of exposure and typically has one or multiple transdermal bites or scratches where the animal’s teeth or claws puncture the full thickness of the skin, causing bleeding. Such wounds carry the highest risk of rabies transmission as the virus-laden saliva has a direct pathway into the body’s tissues and potentially the nervous system. If the animal licks a person’s eyes, nose, mouth, broken skin (or wound), or any other mucous membrane, that’s also category 3 exposure. Any direct contact with bats can be very tiny and go unnoticed but is often treated as category 3.
The recommended treatment for category 3 exposures involves immediate and thorough wound washing and rabies vaccination, along with a rabies immunoglobulin (RIG) shot which provides the immediate antibodies to neutralise the virus at the wound site, offering crucial passive protection while the body develops its own immune response from the vaccine.
Does the bite site play a key role in prevention?
Yes, it does. The rabies virus travels along the peripheral nerves to reach the brain through the spinal cord. If a bite is on the head, neck, or face, the virus has a shorter distance to travel, which can lead to a shorter incubation period and faster onset of symptoms. Prompt and aggressive medical response is critical in such cases. Areas with a lot of nerve endings, such as fingers and toes, also pose increased risk as the virus can easily find a nerve to latch on to. Of course, category 3 wounds, deep bites, contamination of mucous membranes, or broken skin allow more direct access for the virus, whereas a superficial scratch or lick on intact skin carries a much lower risk.
What about the risk of a higher viral load in the animal?
The amount of rabies virus present in the biting animal’s saliva directly impacts the likelihood of transmission. An animal in the later stages of rabies (when the virus has multiplied significantly and spread to the salivary glands) will typically have a higher viral load in its saliva. If it bites, more virus particles are introduced into the body and can enter the nervous system to cause infection. This can overwhelm the local immune response much before vaccination takes effect and contribute to a shorter incubation period before symptoms appear.
Last month, three children died in Kerala even after rabies shots, raising questions about quality. Why are such deaths happening despite vaccinations? Aren’t the vaccines effective?
Anti-rabies vaccines are incredibly effective. But, in some cases, they may fail owing to several factors, including the time of vaccination, dosage, and the type of wound care. For instance, if someone is bitten by a rabid animal and has a category 3 wound, then getting the vaccine right away, along with a rabies immunoglobulin shot, is crucial to make treatment 100% effective in preventing the disease. Also, the person must complete the full vaccination course — day 0, 3, 7, 14, and 28 for most intramuscular route vaccinations and day 0, 3, 7, and 28 for most intradermal vaccinations. Many skip vaccinations if they see the wound heal or if they don’t see visible wounds, both of which are wrong.
What is a category 3 wound? Why is it so serious?
Doctors classify wounds into categories to determine appropriate post-exposure treatment for rabies. Category 3 is considered the most severe type of exposure and typically has one or multiple transdermal bites or scratches where the animal’s teeth or claws puncture the full thickness of the skin, causing bleeding. Such wounds carry the highest risk of rabies transmission as the virus-laden saliva has a direct pathway into the body’s tissues and potentially the nervous system. If the animal licks a person’s eyes, nose, mouth, broken skin (or wound), or any other mucous membrane, that’s also category 3 exposure. Any direct contact with bats can be very tiny and go unnoticed but is often treated as category 3.
The recommended treatment for category 3 exposures involves immediate and thorough wound washing and rabies vaccination, along with a rabies immunoglobulin (RIG) shot which provides the immediate antibodies to neutralise the virus at the wound site, offering crucial passive protection while the body develops its own immune response from the vaccine.
Does the bite site play a key role in prevention?
Yes, it does. The rabies virus travels along the peripheral nerves to reach the brain through the spinal cord. If a bite is on the head, neck, or face, the virus has a shorter distance to travel, which can lead to a shorter incubation period and faster onset of symptoms. Prompt and aggressive medical response is critical in such cases. Areas with a lot of nerve endings, such as fingers and toes, also pose increased risk as the virus can easily find a nerve to latch on to. Of course, category 3 wounds, deep bites, contamination of mucous membranes, or broken skin allow more direct access for the virus, whereas a superficial scratch or lick on intact skin carries a much lower risk.
What about the risk of a higher viral load in the animal?
The amount of rabies virus present in the biting animal’s saliva directly impacts the likelihood of transmission. An animal in the later stages of rabies (when the virus has multiplied significantly and spread to the salivary glands) will typically have a higher viral load in its saliva. If it bites, more virus particles are introduced into the body and can enter the nervous system to cause infection. This can overwhelm the local immune response much before vaccination takes effect and contribute to a shorter incubation period before symptoms appear.
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