Wednesday, July 11, 2007

Vaccines--Hep A

Two doses of Hep A are required for school attendance. The MTC also recommends this vaccination for any missionaries who will be traveling internationally. (The CDC suggests that risk is negligible in USA, Canada, Western Europe, Scandinavia, Japan, Australia, and New Zealand. Risk is particularly high in Central and South America, Asia, the Middle East, most parts of Africa, and the Western Pacific.)

Hepatitis A vaccines come in 3 forms: Havrix, VAQTA, and Twinrix (which is a Hep A/Hep B combo). Havrix contains the preservative 2-phenoxyathenol, while VAQTA has no preservatives, however the CDC warns that neither is approved for administration to a child under the age of 2. I could not find information about approved ages for Twinrix, but considering that it contains the same Hep A as the others, I presume that the >2 years old guideline holds. [update--Twinrix is an adult dose, and only approved over age 18, so it's not a valid option if you are considering it for childhood vaccinations.]
Full vaccination consists of 2 doses, a minimum of 6 months apart. The vaccination schedule recommends giving this vaccine between the ages of 12-24 months (did they not read the Pink Book?! The CDC even put the "not approved under 24 months" part in boldface!)

Hepatitis A is the most common form of Hepatitis reported in the United States. It is often thought of as a foodborne illness, but that is not entirely accurate. Hep A is actually acquired via fecal-oral transmission (yes, you heard that right--you get sick when poo from an infected person gets into your mouth). So, in other words, if someone with Hep A neglects to wash their hands after using the toilet, and then handles your food, then yes, you could get Hep A 'from food'...but it wasn't really the food.
In the United States, approximately 14% of reported cases of Hep A come from 'personal contact' with an infected person (this could be sexual, or just regular household contact such as diaper changes, cleaning the bathroom, etc). 10% of cases came from male homosexual activity; 8% were daycare related; 6% drug use; 5% international travel; and 4% foodborne. However, since 45% of Hep A infections came from 'unknown sources,' we actually have no way to know if any of the data here is actually correct...
Risk groups for Hepatitis A are: international travelers, homosexual men, illegal drug users, those with blood clotting disorders, and people who work with Hep A-infected primates. Food handlers, health care workers, and waste management workers are NOT at increased risk, although their diligence or negligence could affect the risk of others.

As an interesting note, Hepatitis A rates are disproportionately high in the western part of the United States in recent decades. Between 1987-97, 11 states (AZ, AK, OR, NM, UT, WA, OK, SD, ID, NV, and CA) reported 50% of the nation's cases of Hep A, in spite of the fact that they have only 22% of the nation's population. So, for those living in those states, I would infer that risk is somewhat higher than for those residing in other parts of the country.

If one is infected with Hepatitis A, it is almost always very mild. The highest rates of infection are between the ages of 5-14 years old, but as many as 70% of children under age 6 are asymptomatic (this means that the virus gets into their system, but nothing happens). Asymptomatic infection does increase the risk for those around the child though, since nobody knows they are infected, and may not take proper hygenic precautions (with a potty-training child for example). In older people, asymptomatic infection is not common, and >70% get jaundice.
Hepatitis A is fatal in about 0.3% of acute cases (increasing to 2% of cases where the person is over 40 years old). That may be an inaccurately high number though, since so many cases are asymptomatic that it is virtually impossible to know how many people are or have been actually infected.

In the event of an outbreak, vaccination seems to be effective at disrupting continued spread of the infection.
At this time, no serious reactions have been attributed to any Hep A vaccine. The vaccines are too new for comprehensive studies to be completed about duration of efficacy, however the CDC estimates that immunity is effective for 20+ years.

My conclusions:
While the true danger of this disease seems minimal, and the risk of acquiring it also fairly low, it does seem a wise precaution for international travel--especially to third world countries. Considering that we hope/plan to travel, and also that we live in one of those western states, we will be getting this vaccine for our children, however we will wait until they are at least 2 before beginning the series.

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