How does a rabies vaccine work?

Subject: Health

The death of a 12-year-old girl in Kerala from rabies, despite having multiple inoculations of the vaccine, has raised questions on the efficacy of rabies vaccines in India and their availability.

How does a rabies vaccine work?

Rabies is a disease that is caused by a family of viruses called the lyssaviruses and found in a range of mammals. The virus targets the central nervous system and is nearly 100% fatal to the host animal if it succeeds in infecting it. Though many animals from cats to crocodiles can be transmitters of the virus, it is most likely to spread to people from the bite of an infected dog or a cat as they are the most common pets.
Despite being potentially lethal, the virus is slow-moving and it can be several weeks before the disease manifests into a fatal encephalitis which is why administering a vaccine, even after being bitten by a rabid animal, is effective.
A shot of rabies immunoglobulin (rabies-antibodies against the virus derived either from people or horses) followed by a four-week course of anti-rabies vaccine, is nearly guaranteed to prevent rabies. This translates to the first dose being given on the same day as the immunoglobulin followed by vaccinations on the 3rd, 7th and 14th day. There are other regimens, such as five shots which include one on the 28th day approved by the World Health Organization (WHO) which clinics may consider, depending on the availability of the vaccine.

How is the vaccine made?

The vaccine is made up of an inactivated virus that is expected to induce the body into producing antibodies that can neutralise the live virus in case of infection. There are also test vaccines that involve genetically modified viruses. There is no single-shot rabies vaccine or one that offers permanent immunity.
There are mainly two ways of administering the rabies vaccine. One, called post-exposure prophylaxis (PEP), is given to persons who have been exposed via a bite to an animal suspected to be infected. The vaccines are administered either into the muscles, or into the skin.
It can also be given ahead of time to persons who have a high risk of being infected, such as veterinarians, animal handlers, areas with a high number of rabies infection, by what is called Pre Exposure Prophylaxis (PrEP). The advantage of a PrEP is that if bitten, one doesn’t need a immunoglobulin injection, and two subsequent shots of the vaccine will suffice for full protection, unlike the four-course prescription in the case of PEP. However, the WHO doesn’t recommend PrEP as a general preventive.

Are rabies vaccines easily available in India?

According to the Health Ministry, there are at least six rabies vaccines approved for India. They all contain inactivated virus made of duck, chicken or human cell cultures and are marked as safe, efficacious and with long immunity. Rabies vaccines are available for free in government dispensaries though vaccines administered in a private clinic can cost up to ₹500 per dose.
The WHO says India is endemic for rabies and accounts for 36% of the world’s deaths. The true burden of rabies in India is not fully known; although as per available information, it causes 18,000-20,000 deaths every year.

What about vaccines for animals?

Given that rabies treatment requires multiple shots of vaccine as well as immunoglobin, sticking to the schedule is challenging. Governments of countries where rabies is endemic have frequently set targets to eliminate the disease — India has committed to do so by 2030. Yet it is widely acknowledged that this elimination requires vaccination of dogs. Like in people, vaccinating animals too doesn’t guarantee lifelong immunity from the disease. Because dogs are deemed responsible for 99% of all rabies infections in people, the government in its 2021 plan, called the ‘National Action for Plan — Rabies Elimination’, aims to vaccinate at least 70% of all dogs in a defined geographical area annually for three consecutive years. With this, a degree of herd immunity is expected leading to eventual elimination within eight years. Rather than inoculate all dogs, which is not feasible, the plan is to identify ‘rabies hotspots’ across the country and target them.