What’s New in Vaccines
New vaccines to protect travelers against hepatitis A and typhoid fever could be on the U.S. market soon, and other vaccines to prevent other travelers’ ills are under study.
Here’s a rundown on what’s new in the vaccine race, along with expert advice on how travelers can best protect themselves from disease.
* Havrix, a hepatitis A vaccine developed by SmithKline Beecham, is awaiting federal Food and Drug Administration approval before it can be sold in the United States, but industry experts predict approval could come within the next few months, possibly before the end of the year.
Hepatitis A, one of five known variants of the disease, is a common problem for travelers in developing countries. It is marked by liver inflammation, and symptoms include swelling, fatigue, fever and muscle and joint aches.
The disease is transmitted through a variety of foods and drinks, including contaminated water, ice and shellfish.
The vaccine works by stimulating the body’s defense mechanism just as a natural infection would, but without causing an infection. Two injections are required, according to Sharyn Arnold, a spokeswoman for SmithKline Beecham, and it takes effect about two weeks after the last dose. Based on clinical trials, it’s expected to be 97% effective.
This, the newest of a new breed of hepatitis A vaccines, is considered superior to the immune globulin injections currently used to protect against hepatitis A because it is expected to confer longer-lasting protection.
* VAQTA is another hepatitis A vaccine. It was developed by Merck & Co., which has not yet filed for FDA approval, according to a spokeswoman. In a study of 519 subjects published in the New England Journal of Medicine in 1992, the vaccine was found to be 100% effective.
Guidelines on who might benefit from the new hepatitis A vaccine are being drafted by the Centers for Disease Control and Prevention, according to Dr. Beth Bell, a medical epidemiologist in the hepatitis branch.
Ideal candidates will probably be people under age 50 who have never had hepatitis A and who travel overseas frequently to areas where it is prevalent, said Dr. Stuart Rose, an emergency medicine physician in Northampton, Mass., and author of the “International Travel Health Guide” (Travel Medicine, Inc., $17.95). (It is thought that people over 50 are more likely to have been infected with hepatitis A because they have probably traveled more extensively.)
Travelers who don’t know whether they have been exposed and as a result have developed immunity, can get a blood test to find out, Rose said.
* Typhim Vi, a typhoid fever vaccine, is awaiting FDA approval, said Linda Mayer, spokeswoman for Connaught Laboratories, Inc., Swiftwater, Pa. The inactivated (or “killed”) vaccine is given in one injection, Mayer said, and was developed by Connaught’s parent company, Pasteur Merieux Serums & Vaccins in France.
Typhoid fever is caused by Salmonella typhi, a type of salmonella bacteria, and is transmitted by contaminated food or water. The first symptoms are flu-like, including chills, fever and vomiting. It is prevalent in many countries of Africa, Asia and Central and South America, according to the CDC.
An existing oral vaccine and several different types of injected vaccines against typhoid fever are about 70%-90% effective, according to the CDC.
The oral typhoid vaccine currently on the market requires four doses over eight days, Rose said. Travelers take three doses home and must store them in the refrigerator. Such variants as storage temperature might reduce effectiveness, he said.
The new Typhim Vi is also about 70%-90% effective, said Mayer of Connaught Laboratories. But its single dose is more convenient than the oral vaccine, she added.
* A new cholera vaccine, called CVD 103-HgR, is under study by Dr. Robert Edelman at the University of Maryland’s Center for Vaccine Development. It is effective against classical cholera and El Tor cholera, he said, but not the newer strain, Bengal (or 0139), first recognized in India about a year ago.
“We are working on a vaccine for this (Bengal) strain now,” he said. “We hope to add something to the vaccine we’ve got so it will cover all (types of) cholera.”
The CVD 103-HgR is an oral vaccine that protects against classical and El Tor cholera within eight days, Edelman said. The current cholera vaccine is not considered effective.
Cholera is caused by toxin-producing bacteria called Vibrio cholerae , found in contaminated food and water.
The disease usually responds well to treatment, which includes rehydration and antibiotics. Often, cholera is mild and produces few or no symptoms. But if large amounts of bacteria are ingested, symptoms can be severe, including watery diarrhea, muscle cramps and vomiting.
Depending on destination, travelers--particularly the elderly--should also ask their physician if they should be vaccinated against influenza and pneumonia, Rose said.
Travel medicine physicians agree on another point: While vaccines provide protection against diseases, none are perfect.
That’s reason enough for travelers to follow common-sense precautions, such as avoiding food or drink that might be contaminated.
