Typhoid fever and its vaccine – Who? What? Where? Why?

Typhoid fever? What’s that?

I’m sure you’ve heard about Salmonella, correct?
As I mentioned in my post about Salmonella, this is a family of bacteria named after the American veterinarian, Dr. Daniel Salmon, who discovered it at the time.
The Salmonella family is divided into different groups, two of these groups are the Typhoidal (Typhi) Salmonella group and the Non-typhoidal (Non-typhi) Salmonella group.

The Salmonella that causes typhoid fever, which is also known as enteric fever, is referred to as Salmonella typhi (and also para-typhi), and the salmonella vaccine that exists is for this type only.

The infection presents with fever (usually high), headaches, abdominal pain, weakness, fatigue, loss of appetite, a characteristic rash in about 30% of the cases, diarrhea and more. The infection itself is unpleasant, to say the least, and carries many potential complications.

One of my late teachers, Professor Mervin Shapira, may his soul rest in peace, who was one of the best infectious disease specialists I have ever known, used to joke about how they used to diagnose typhoid fever back in the day with the help of the “fly test”.
These were his words: If your patient has a fly on their nose and has no energy to lift his arm to shoo the fly away, that is when you know they have typhoid fever.
Nobody wants to catch this disease.

In which parts of the world can this infection be found?

Salmonella typhi is distributed everywhere in the world, but it is less prevalent in eastern countries. Its prevalence is higher in developing countries, particularly in Asia.

How does Salmonella typhi spread?

Salmonella typhi is transmitted through the fecal-oral route. That means, it spreads when one eats or drinks food or beverages that were contaminated by someone who had the infection or is a carrier of the bacteria. People can remain carriers for over a year following their primary infection, which means that even those who are healthy and feeling well can spread the infection.

How long is the incubation period and why is this important?

The term ‘incubation period’ is important in infectious diseases. It describes the length of time that it takes for clinical manifestations to occur following transmission of the bacteria (in this case it is the swallowing of the salmonella bacteria by the person).
In typhoid fever the average incubation period is 7-14 days while the interval can range from 3-60 days.
Why is this important? If someone was visiting Nepal, for example, and they develop fever and diarrhea 30 days after they return home, it is possible that they have typhoidal fever, and the physician needs to consider this diagnosis when assessing them.

How can typhoid fever be avoided or prevented?

There are two ways to do this and they are complementary to one another: hygiene and vaccine.
Hygiene – this is especially true when it comes to preparation of food and drinking water and includes hand hygiene before eating and after using the toilet.
Vaccine – before travelling to developing countries.
Who should and who should not get the vaccine? More about this below.

Which travellers should not get the salmonella typhoid vaccine?

My apologies. I know it is slightly confusing to start by mentioning the people who should not be getting the vaccine, but if you are familiar with this group it gets easier to explain the group of people who do need the vaccine. So, my apologies but please stay with me.

Travellers who do not need the vaccine:
# Travellers who are travelling for a short period of time, when the destination is urban and they intend on staying at a high quality hotel.
# Business travellers
# Travelling with an organized tour, for a period of time that does not surpass 4 weeks, including short, non-organized trips

Which travellers should get vaccinated?

# Travellers travelling with an organized tour, who intend on visiting areas that may be at high risk of infectious diseases due to poor sanitation or may be at risk of close contact with locals
# Travellers who are foodie adventurists and like to experiment with local foods
# Travellers to India or Nepal. Everyone travelling to India or Nepal needs to get vaccinated.
# Travellers taking backpacking trips or travellers on organized tours that may include backpacking trips and are travelling for longer than 4 weeks
# Travellers that regularly travel to endemic areas, be it for business, pleasure or visiting family

Why are the guidelines for who needs to get vaccinated problematic?

The problem with the above recommendations is that they are not very clear. What does it mean to be in close contact with locals? What does a backpacking trip entail?

It is clear to all of us that it is impossible to be 100% accurate when it comes to guidelines. It is difficult to answer questions that may be posed by travellers such as “I am travelling for 4.5 weeks but I do not plan on being in close contact with any locals, do I need to get vaccinated?” or “I am travelling to Thailand for 2 weeks but I plan on visiting the northern part of the country, should I get vaccinated?”.

That is why it is best to refer to your primary healthcare professional to get more information about whether your specific travel plans require a vaccine. If in doubt, it is best to consult with a travel medicine specialist and keep in mind that the things are constantly changing. Salmonella typhi outbreaks can occur anywhere in the world, even in areas that had a low prevalence of disease just one month ago, and so every time you plan on travelling to an exotic country, it is important to repeat the consult.

What are the different types of vaccines available for typhoid fever?

Typhim Vi – a polysaccharide vaccine that is practically inactivated (not live attenuated), intended for use in children over the age of 2 years and adults. This vaccine is given as one dose.

Vivotif – this is a live attenuated vaccine that contains live cells from the Salmonella typhi bacteria and in North America it is intended for use in adults and children over the age of 6 years. These are capsules that need to be taken on an empty stomach, at least one hour before your next meal. One capsule is taken every other day. There is a total of 4 capsules. The capsule must not be chewed or mashed and that is why this vaccine is only relevant for children who are able to swallow capsules. Note that in different parts of the world the minimum age requirement and number of capsules taken may vary.
Also, keep in mind that anyone with a congenital or acquired immune deficiency cannot receive live attenuated vaccines.

Typbar – this is a conjugated vaccine that is practically inactivated (not live attenuated), and is manufactured in India. It can be given to infants as young as 6 months. Is it given as one injection and is not available in western countries despite being more effective than the previous two vaccines I mentioned above.

What are the possible side effects of the vaccine?

Luckily for us, the prevalence of side effects caused by the first two vaccines is quite low.
The polysaccharide vaccine administered as an injection may cause local tenderness, fever, headaches, muscle pain and fatigue.
The live attenuated vaccine dispensed as capsules may cause abdominal pain, vomiting, diarrhea, fever, headaches and a rash.

When is the best time to get vaccinated if you plan on travelling?

To allow the body to develop sufficient antibodies prior to your trip, the polysaccharide vaccine must be administered at least 2 weeks prior to your trip while the live attenuated vaccine should be given at least 1 week before travelling.
However, if you are travelling to an area that is at high risk, get the vaccine even if you are travelling in less than a week.

What about pregnant women?

Since there is no medical information about the safety of the polysaccharide vaccine in pregnant women, we tend to consider the benefits and weigh them against the risks and make a case-based decision.
As for live attenuated vaccines – these are not permitted during pregnancy.

How effective are these vaccines?

The efficacy of the vaccines lies between 50-80%
What does this mean in practice? Even those who have received the vaccines must be careful and maintain adequate hygiene.

How long does vaccine immunity last?

The answer to this question depends on where you live.
In North America, immunity acquired through the inactivated polysaccharide is assumed to last 2 years while the live attenuated vaccine immunity is assumed to last 5 years.

I am travelling and have diarrhea and I’m afraid I may have caught typhoid fever, what should I do?

First, keep in mind that diarrhea can be caused by many different pathogens, especially when you are visiting an endemic country. However, if you have high fever and significant diarrhea, see a physician. Be aware of whether your diarrhea is bloody or contains mucous. Read more about why this is important here.

There are people who purchase antibiotics for salmonella typhi before going on their trip and start taking them while abroad following a consult with their healthcare provider. Consult with your healthcare provider to find out whether you should do this before travelling.

In summary, this post has taught us lots of new things. We learned about incubation period and also about the fly test. We are now familiar with two typhoid fever vaccines. We have also learned that it is important to see a travel clinic before travelling to exotic destinations.

Enjoy your trip my friends!