Ari's Planet

I have received the following vaccinations (in addition to the usual required in the US):

Tetanus booster
Diptheria booster
Polio booster
Typhoid
Hepatitis A
Hepatitis B
Yellow fever
Meningitis
Rabies preexposure booster

Typhoid was provided as oral tablets containing inactivated typhoid. You take these pills every other day for four doses. The pills must be kept refrigerated to maintain the viability of the organisms.

According to the WHO (REF), risk of infection with yellow fever risk in African countries where it is prevalent is ~1:300, while risk of death is ~1:1300. The risk of the vaccine is much lower than this, with severe complications somewhere on the order of 1 in a million (this is not an actual quoted number, but if you look at the reported number of problems it's somewhere in this ballpark). Severe reactions are more common in people with compromised immune systems or thymus problems. In addition, some countries will deny entry for people arriving from yellow fever endemic countries. Thus, yellow fever vaccination was a good idea.

Meningitis is most prevalent in some central African countries, particularly during the dry season. It is also present elsewhere. It seems like a good idea to get vaccinated.

I had a full rabies course in 1985 following an animal bite. Rabies resistance wears off with time. People, such as veterinarians, who work with potentially rabid animals need boosters every two years to maintain immunity. A three-shot preexposure series is very expensive. It was not clear cut whether I should get a full preexposure rabies sequence given my activities and duration of stay in countries where rabies is more common. My doctor therefore recommended getting a single shot and possibly checking my titer. At the time, I missed getting my titer checked. Walking around India, with its multitude of dogs, I realized a full rabies pre-exposure series would have been advisable. In retrospect, I should have gotten this course, should have checked my titer, and based on material I have read would suggest people get a series if going to India or Nepal. CIWEC medical clinic in Kathmandu also recommends a course for visitors to Nepal.

I did not get immunized for Japanese encephalitis. This disease is present in the Asian countries I will be visiting and can leave lasting and damaging neurologic problems. However, it is mainly recommended for people working outside our remaining for prolonged periods in areas of high exposure, such as agricultural workers. The vaccine carries a higher risk than the other vaccines. In addition, the likelihood of transmission depends also on the climate which varies with the time of year. The vaccine is also expensive and requires a three shot sequence. Very few American travelers have contracted the disease while overseas. This disease is prevalent in SEA. The main season is May to October. I plan to leave SEA by May, reducing my risk. However, now that I am here it would be nice to stay longer in some rural areas. The CDC has information on the risks, and it seems the vaccine is not particularly dangerous: the information hand-outs I was given at the health center were not particularly helpful and were more alarmist on the vaccine than the risks of the disease! In retrospect, I should also have gotten this vaccination. It requires a three-shot series over a month. Adverse effects can appear 2 weeks after inoculation, so one must remain in an area with medical care for 6 weeks (one month for the series and 2 more weeks to monitor for adverse effects). This means I cannot get the vaccine while traveling! Damn.

The transmission season in Laos, Thailand, Vietnam, Cambodia is May-October and in Indonesia peaks Nov-Mar and Jun-Jul in some years, but risk is present year-round and depends on conditions and regions.

From the CDC Faq (quoting another source): "Who should be vaccinated against Japanese encephalitis?"

"Travelers: Japanese encephalitis vaccine is NOT recommended for all travelers to Asia. In general, vaccine should be offered to persons spending a month or longer in endemic areas during the trans-mission season, especially if travel will include rural areas. Under specific circumstances, vaccine should be considered for persons spending <30 days in endemic areas, e.g., travelers to areas experiencing epidemic transmission and persons whose activities, such as extensive outdoor activities in rural areas, place them at high risk for exposure. ... Estimates suggest that risk of Japanese encephalitis in highly endemic areas during the transmission season can reach 1 per 5,000 per month of exposure; risk for most short-term travelers may be 1 per million. Although Japanese encephalitis vaccine is reactogenic, rates of serious allergic reactions (generalized urticaria or angioedema) are low (1 to 104 per 10,000)."

The upshot is if I don't hang around rice paddies and conclude my travel in the area by May, which is my plan, then my risk for JE is relatively low. The CDC page on JE quotes "Based on postmarketing surveillance data, the reported rates for allergic adverse events following the administration of inactivated mouse brain-derived JE vaccine doses were 0.8 and 6.3 per 100,000 doses in Japan and the United States, respectively." It was these statistics on the relative risk of contracting the disease versus risk from vaccination that originally convinced me not to get the vaccine.

This article seems to exactly cover my concerns:

http://www.journals.uchicago.edu/doi/abs/10.1086/341247
Clinical Infectious Diseases 2002;35:183–188
DOI: 10.1086/341247
TRAVEL MEDICINE
David R. Shlim and Tom Solomon
Japanese Encephalitis Vaccine for Travelers: Exploring the Limits of Risk

I love the introduction. The article cites the risk to travelers as 1 in a million chance of contracting the disease, which is actually 10 times greater than the risk to Americans of contracting meningitis. To help put risks in perspective, they also cite a study that put the risk of death from trekking in Nepal at 15 in 100000. Later, it cites CDC work that, eliminating travelers who stayed only in urban areas, came up with a range of 1:5000 to 1:20000 per week, significantly higher. Their recommendations for travelers to which vaccine should be given are: "persons who will be spending time living in a village setting near rice paddies and farm animals during a season of transmission ... bicyclists, backpackers, and other adventure travelers whose itinerary is uncertain but may include significant time in areas of endemicity". Again, I won't be in these regions during the transmission season, so I guess the recommendation that I not get the vaccine was valid.

CDC Thailand http://wwwn.cdc.gov/travel/destinationThailand.aspx
CDC Vaccinations http://wwwn.cdc.gov/travel/contentVaccinations.aspx
CDC Japanese Encephalitis http://wwwn.cdc.gov/travel/yellowBookCh4-JapaneseEncephalitis.aspx

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1708-8305.2006.00092....
Stephen Toovey MBBCh, CTM, FACTM, FFTM, Filip Moerman MD, DTM, MSc, Alfons van Gompel MD, DTM (2007) Special Infectious Disease Risks of Expatriates and Long-Term Travelers in Tropical Countries. Part II: Infections Other Than Malaria
Journal of Travel Medicine 14 (1) , 50–60 doi:10.1111/j.1708-8305.2006.00092.x

http://www.blackwell-synergy.com/doi/abs/10.2310/7060.2005.00006
Steffen Robert, Connor Bradley A. (2005) Vaccines in Travel Health: From Risk Assessment to Priorities
Journal of Travel Medicine 12 (1) , 26–35 doi:10.2310/7060.2005.00006