We receive a number of queries regarding immunizations. We often disappoint people by not giving specific answers to general questions. I d like to take a minute to explain why it is important that you always get specific information from a physician who is familiar with your case (as we will be if you participate in our travel advice program.)
An immunization is something given to you to help your body s own immune system ward off a disease. Most of the time this is in the form of a shot or oral dose of some form of the bacteria or virus which causes the disease. Some vaccines use ground up parts of the organism while others use an actual, slightly weakened live organism. Your body then forms antibodies to this organism so that the next time it sees it, it is ready to fight it. It usually takes at least 10 days for these antibodies to form. Depending on the disease and on the efficacy of the vaccine, you may keep producing adequate antibodies to render you immune for the rest of your life, or they may last only as long as a few months.
Another form of immunization, called passive immunization, takes antibodies already formed by another person and injects them directly into you. This is usually in the form of gamma globulin. The advantage to this is that it can be given after exposure and is instantly effective. The disadvantages are that the shots are painful, they are available for only a few diseases, and they are made from human blood products which means there is a risk of transmission of hepatitis, HIV, etc. That risk is almost non-existent in the U.S. but not always so elsewhere.
When traveling, you need to distinguish between required and recommended vaccinations. Required immunizations are those that you have to have in order to be legally allowed into a country. This is for the protection of the country TO which you are traveling and will often depend on where you are coming FROM. It s their way of protecting their citizens against you. Right now, the only required vaccination in any country is Yellow Fever. BUT you sometimes run into local health officials who require certain shots even though their country officially does not. Cholera is a frequent case in point. So you need to know not only what is officially required, but also what is required in actual practice. (Along this same line, there are now about 45 countries which may require an HIV test, depending on how long you plan to stay. Enforcement of this can be unpredictable as well.)
Recommended immunizations are for YOUR benefit--to protect you from diseases you might encounter.
There are routine ones, like tetanus, polio and flu which you really should be up to date on whether you are traveling or not. Then there are special ones like yellow fever, cholera, rabies, etc. which depend on your risk of exposure when you travel.
And herein lies the rub. What is recommended for any given locale may vary tremendously from person to person, and depending on what has happened in that locale lately. Vaccines vary tremendously in efficacy. Some may be only 50% effective so, if your risk of exposure is minimal, then simple health measures like watching what you eat or drink, protecting yourself from insect bites and not swimming in contaminated water may work just as well. Even highly effective vaccines may be so expensive or have such risks of side effects that they are not worth getting in all but high-risk situations. The newer rabies vaccines are excellent examples. The side effects can be deadly (rarely), but since rabies is 100% fatal you re better off with the vaccine--IF you are at high risk of exposure. Also, new vaccines are becoming available at a rapid pace, so what was true last year or even six months ago may no longer be true now.
That's why it is important you get your own, personal, up-to-date advice from a physician who not only knows the international infectious disease scene but also knows you, your health problems, and your specific itinerary.
You can save yourself a lot of trouble by keeping your routine immunizations up to date at all times. Then, when you travel, see the appropriate travel medicine specialist at least two months in advance for the special immunizations you need. Sometimes in an emergency the needed shots can be compressed into a shorter time but usually they will be less protective. Some immunizations can be given simultaneously, some can t. And some require a series of shots, not just one. Special circumstances, such as pregnancy or taking antibiotics, may interfere with adequate vaccination. Immune suppressed states like cancer, chemotherapy or HIV may also radically alter what is advisable. And personal allergies always enter in somewhere. Children, also, often need more shots than adults since they are more prone to risky activities. If shots simply cannot be given then sometimes an explanatory letter from a physician will suffice. You may have to check with an embassy. But you may just have to change the itinerary. Do make sure that whatever shots you have are correctly recorded in the right place on the right form and signed by the right person.