Quick Answer
The recommended time to get a rabies shot after being bitten is as soon as possible. According to the CDC, rabies shots are most effective when given right after exposure before the rabies virus has time to spread through the body. However, rabies has a long incubation period, so there is still time to get vaccinated after a delay. Rabies shots are still recommended regardless of the time interval between the bite and seeking treatment, as long as symptoms of rabies have not yet appeared.
What is the time frame to get the rabies vaccine after a bite?
The rabies vaccine should be given as soon as possible after a potential rabies exposure. The CDC recommends the following time frames:
- Immediately seek medical evaluation and rabies vaccination if bitten by a wild mammal or a domestic animal that is not up to date on rabies vaccinations.
- If evaluation is delayed, get vaccinated as soon as possible. Do not wait for symptoms to appear before getting vaccinated.
- Even if months or years have passed since the exposure, rabies vaccination should still be given if symptoms consistent with rabies have not appeared.
The key point is that while immediate vaccination is ideal, it can still be effective for some time after exposure. As long as the person bitten does not yet show symptoms of rabies, the vaccine and immunoglobulin can still potentially stimulate an immune response fast enough to prevent the rabies virus from infecting the central nervous system.
How long does it take for rabies symptoms to appear after a bite?
The incubation period for rabies, meaning the time from infection to onset of symptoms, can vary greatly:
- In humans, the incubation period typically ranges from 3-12 weeks after exposure, though it can be as short as days or longer than years.
- On average, symptoms begin after 3-8 weeks in humans.
- The incubation period tends to be shorter in bite wounds on the head, face, or neck compared to the extremities.
- Factors like the amount of virus in the animal’s saliva, severity of the wound, and proximity to the brain also play a role.
Due to the potentially long incubation period, there is time to get vaccinated after exposure as long as symptoms have not progressed. This wide window is why rabies vaccination is warranted even years after the bite occurred.
How does the rabies vaccine work after exposure?
The rabies vaccine works by stimulating the immune system to produce antibodies that can neutralize the rabies virus.
When given after exposure, it works in two ways:
- Prevents infection of cells: The antibodies can bind to virus particles and prevent them from entering and infecting cells.
- Clears infected cells: Antibodies also recognize infected cells displaying viral proteins on the surface and stimulate other immune cells to destroy them.
As long as enough antibodies can be produced and activated before the virus spreads to the nervous system, the infection can be halted. The vaccine is most effective in the period immediately after exposure since the virus load is still low. However, it remains beneficial at any point before symptoms start.
Why delay lowers effectiveness
A longer delay before getting vaccinated decreases effectiveness because in that time, more virus replication can occur leading to a higher viral load and greater infection of cells. The antibodies then have more work to do to contain the infection. Starting vaccination when virus levels are still low improves the chances of success.
What is the recommended rabies post-exposure treatment?
The CDC recommends a thorough washing of the wound with soap and water, followed by immediate vaccination with:
- Rabies immune globulin: Providesimmediate short-term protection by directly neutralizing virus particles.
- Rabies vaccine: Stimulates the immune system’s production of antibodies for long-term protection. Several doses are given over 14 days along with the first dose of vaccine.
This combination is highly effective at preventing rabies if given promptly after a bite from a rabid or possibly rabid animal. Depending on the type of contact, immune globulin may not be needed. Only the vaccine itself may be given in cases of licks on broken skin or exposure to blood, saliva, or brain/nervous tissue.
Vaccination schedule
The rabies vaccine is given as a series of 4 doses over 14 days:
- First dose: Given as soon as possible after exposure, along with the immune globulin.
- Additional doses: Given on days 3, 7, and 14 after the first vaccine dose.
These boosters stimulate a robust antibody response essential for neutralizing the virus.
Can rabies develop if vaccination is delayed?
Yes, it is still possible to develop rabies even if vaccination is delayed, though the risk decreases if it is given before any symptoms start.
Reasons why rabies could still develop after late vaccination:
- The virus may have already infected nervous system cells that antibodies cannot reach.
- The immune response was not robust enough to control the viral load.
- Symptoms began very soon after the bite, before the vaccine took effect.
However, the rate of vaccine failure is very low if it is administered promptly. In one study, no patients developed rabies after getting the recommended postexposure treatment within 10 days even without prompt wound care.
How long does the rabies vaccine last after exposure?
After getting the full postexposure rabies vaccine series, protection is long-lasting.
- CDC: Immunity after vaccination persists for at least 10 years, and likely longer.
- Those at continual risk should get a booster dose every 2-5 years.
- Monitoring antibody levels is not useful for determining waning immunity after vaccination.
Unlike the period immediately after exposure, a delay of years from the last vaccine booster to re-exposure is unlikely to impact effectiveness as long as some baseline immunity remains.
What if too late for the vaccine?
If symptoms of rabies develop, it is too late for the vaccine to work and the disease is nearly always fatal. However, a life-saving treatment option exists:
- The Milwaukee protocol is an experimental approach that involves putting the patient into a coma and giving antiviral drugs.
- This aims to bypass the brain and allow the immune system time to fight the virus.
- Fewer than 10 patients have survived this protocol to date.
- Outcomes are generally poor once clinical symptoms appear, underscoring the urgency of getting vaccinated as early as possible after exposure and not waiting for symptoms.
Key points
- Get the rabies vaccine and immunoglobulin as soon as possible after any potential rabies exposure for the best chance of stopping infection.
- Rabies vaccination is still warranted and can be effective for days to years as long as symptoms have not appeared.
- The average incubation period of 3-8 weeks leaves a window where postexposure vaccination can still stimulate an antibody response to control infection.
- With increasing delays, the risk of rabies rises but remains low if vaccination occurs before any symptoms start.
- Once symptoms appear, prospects for survival using the Milwaukee protocol are grim, underscoring the critical need for prompt vaccination.
Conclusion
While immediate rabies vaccination after a potential exposure is ideal, the vaccine remains highly effective for a period of time after delays thanks to the virus’s typically long incubation period. However, the sooner treatment begins, the better the chances of preventing progression to full-blown rabies. Regardless of the time interval, vaccination is strongly recommended following any bite or contact with a rabid or potentially rabid animal as long as symptoms consistent with rabies are not yet present. Public education on seeking prompt medical care even with remote exposures can go a long way in preventing this dangerous infection.