Salmonella typhi is the name of the bacteria that is the offender behind these infections, and though there are a couple of versions of the vaccine available, the live version might be preferable for a few reasons. Basically, it goes by the name of Ty21a and can be delivered orally to those who are the most susceptible, that being (in the United States) foreign travelers who have intentions of visiting India, Pakistan, or Bangladesh. With an efficacy of only about 48% in the first few years, it is still important that people in at-risk areas avoid the most commonly known sources such as bad drinking water, poor sanitation, or contact with other infected people. This is one of the two versions of the typhoid vaccine that is recommended currently by the World Health Organization (WHO).
The symptoms of a typhoid infection can range from quite mild to severe enough to cause death like it does for about 145,000 people per year globally. These symptoms will generally be realized at the second week to a month after the exposure occurs, and these symptoms can include everything from a basic headache or abdominal pain to the more troublesome confusion with mental and physical weakness. As an enteric fever, there may also be an accompanying skin rash with rose-colored spots, and so the best chance of avoiding all of this completely if one has to be in the vicinity is to utilize the live typhoid vaccine known as Ty21a. Vivotif is the trade name of the product, and it is a drug that is manufactured by PaxVax and requires a prescription in the United States, the United Kingdom, Australia, and most other countries where its use is seen.
Live attenuated vaccine
Studies have been done on the Ty21a live version of the vaccine, and the results have shown that there is no significant reactogenicity that might be expected in some of the older versions or different variants. In other words, most of those symptoms that usually accompany a typhoid infection do not seem any more likely in a vaccinated group over the control group.
However, it has been shown that a fever can be one adverse event that is more likely to appear in those who utilize the vaccine, but it is generally tolerated well and not likely to impact the patient significantly. HIV or AIDS is an immunodeficiency condition, and as such, it is likely to exacerbate or allow some side effects. But, this depends quite a lot on the T-cell count, and it can likely still be effective if that count (CD4) is greater than 200/mm³. There can also be problems if a patient already is known to have allergies related to any component of the medicine. In such cases, there can be problematic side effects such as diarrhea, fever, stomach/intestinal issues, or vomiting. Proper monitoring and consulting with a physician if any of these things occur is necessary to help avoid severe complications.
Production of this oral vaccine Vivotif requires a process that includes bacteria that are grown in a yeast extract medium. Because of this, it is important that any patient who has been known to have a yeast hypersensitivity or allergic reactions should avoid this version of the vaccine. When the vaccine is being given, the healthcare professional needs to have on hand the epinephrine injection that will be able to combat any anaphylaxis from a severe allergic reaction that can possibly occur in the patients. It is important that this injection and related agents are taken along by the crew of any such immunization youth programs or similar initiatives. This is true for any of the biological products. There is now a Vaccine Adverse Event Reporting System (VAERS) telephone number that has been established by the US Department of Health and Human Services.
The product is basically a live attenuated vaccine that means that the Salmonella typhi is modified in the laboratory in order to reduce its severity, and then it is given an enteric coating in order to help it pass through the stomach and the associated acid before dispersing into the human body. Another option for the live typhoid vaccine is to have it delivered in a liquid suspension. In either case, it is taken by mouth at an interval of two days for about three or four total doses. It is subsequently required that a booster is given at about three years after the initial vaccination if the person is living in an endemic area where they are more likely to encounter the infectious disease. The capsules are usually given to travelers for their protective routine while the liquid suspension has a more prominent role in public health programs like those that help the youth who are being raised in such countries where things like poor sanitation and relative contact with bad water or human waste can be detrimental. However, the vaccine capsules of Vivotif should not be kept at room temperature, but instead, they need to be stored as outlined in the "Storage" section below. When taking, the whole capsule should be swallowed completely at a time of about one hour before a meal, and a colder beverage (not room temperature) used to wash it down with.
Proguanil and other antibacterial drugs should be avoided for at least a span of three days both before and after the consumption of the live typhoid vaccine because of the fact that they are known to be harmful to such live vaccination protocols. Antimalarial agents are another type of product that the manufacturer recommends be avoided for that same span of three days in order to achieve the best efficacy in an individual. Those who are already taking Deflazacort will likely need to either forego the Typhoid vaccine or have a change in prescription according to a doctor's recommendations due to the immunosuppressant properties of such a glucocorticoid. Here is a list of other drugs that are likely to cause some type of interaction so that a doctor will need to either change dosing or timing if they are a necessity:
People who are immunocompromised should avoid this type of vaccination, and there is also a warning out for anyone who has experienced hypersensitivity in the past to any single component of the total vaccine. It is important that a qualified medical professional consider any repercussions if this vaccine is going to be taken at the same time as any other live vaccine within a period of a month. This vaccine will likely not have any effect if given at the same time that a person is experiencing diarrhea. No studies have been done on the effect that may occur on a fetus if given to a pregnant woman, and as such caution and avoidance are currently recommended in order to avoid the chance of any fetal harm.
The ideal storage of the Ty21a live vaccine is at between 2 and 8 degrees Celsius, and it is at this temperature that it will retain its effectiveness for quite some time. That calculates to 35.6 and 46.4 degrees Fahrenheit, and so this live Typhoid vaccine should be kept in a refrigerator but not frozen. It can remain potent at up to 25 degrees Celsius for a period of about two weeks, but after that, a new source will need to be found as that product will no longer be valid. Exposure of the product to any temperatures lower than the aforementioned or greater than that 25 degrees threshold will also invalidate the product so that its efficacy cannot be trusted. The capsules should not be stored in an area where they can be damaged since the effectiveness of the Vivotif live vaccine relies on it being able to dissolve in the intestines for disbursement, and cracked or damage capsules will nullify this process.
Overall, the live typhoid vaccine in the form of Ty21a is a major improvement from those of the past that began appearing first in the late 19th century. This is specifically an advancement in regards to the lack of adverse reactions as well as being an easy formulation to dose so that one can take the treatment and get on with their life. While most of the developed world has built a sanitation and water system that is robust enough that cases of Typhoid being contracted in those countries is generally hardly ever heard of, there are still many third-world countries that do not have these same amenities. For that reason, it is important that any travelers utilize the vaccine and that others help to inoculate those indigent to such regions so that the quite serious infectious disease of Typhoid does not continue to spread or cause deaths.
There needs to be a minimum of at least three doses for adequate protection to take effect, and in the United States and neighboring Canada, it is generally given on alternate days for a total of four doses. Even so, it takes some time for the body to build up immunity to the live typhoid variation that the capsule encloses. It is a week after the last dose that there will be as full of protection as possible, although the efficacy rate is still just 48% according to a study by the Center for Disease Control (CDC). The studies show that the effectiveness in children varies from being significantly greater protection in some cases to almost no protection when given to others. Because of the United States's lack of inherent Typhoid problems, it is generally not recommended that the Ty21a is given as part of a routine vaccination, but rather only for those who are needing to travel to problematic countries. However, the cost and availability of this live Typhoid vaccine has improved to the point that it can be more readily given to those who need it the most such as those children in the urban slums of Asia's major cities and elsewhere. It is now recommended by the WHO to be used for outbreak control due to Typhoid Fever's epidemic potential in such places around the globe. The Ty21a live Typhoid vaccine version has an effectiveness that is statistically significant, especially over the first seven years. There are other sources of enteric disease that come in the form of viruses or other bacteria, but this specific live Typhoid Vaccine is only active against the Salmonella typhi variation. The local immune response inside of the intestinal tract caused by an aborted infection is quite effective at providing protection.