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A shot in the dark: Are we ready for STD vaccines?

Vaccines in the pipeline are delving into new terrain: sexually transmitted diseases. The target audience of young teens poses unique challenges.

By Susan J. Landers, amednews staff. Nov. 3, 2003.

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David I. Bernstein, MD, envisions a future in which a physician would turn to a mom accompanying her daughter for a routine office visit and say, "Oh, she's 13, it's time for these vaccines." The teen would roll up her sleeve, and the doctor would administer a vaccine against human papillomavirus. And maybe another to ward off herpes simplex.

But Dr. Bernstein, professor of pediatrics and director of the division of infectious diseases at Cincinnati Children's Hospital, is also the father of teenage daughters. "I keep thinking, wait, these are my girls we're talking about." He, like most parents, can't imagine that his children will be having sex someday, perhaps sooner than he would want.

Dr. Bernstein's hopes and fears cut to the heart of the debate over many of the vaccines now in the pipeline. They offer the promise of protection from sexually transmitted diseases, but the fact that the target audience is young teens or even preteens might prevent these vaccines from being widely accepted for a number of reasons.

Researchers are working on vaccines that protect against not only HPV and herpes but also chlamydiosis, cytomegalovirus infection, gonorrhea, hepatitis C and HIV. Any single one of these vaccines, if brought to market, could save millions of health care dollars, not to mention the personal toll of disease and death.

Chlamydial infections can cause sterility in women, genital herpes poses a life-threatening risk to newborns, and untreated gonorrhea can cause infections in other parts of the body. Prenatal cytomegalovirus infection is a leading cause of death, mental retardation and deafness. HIV continues to ravage the world's population. A safe and effective HPV vaccine, which many believe will be on the market within the next three to five years, could put an end to the majority of cervical cancers.

But what if no one will use any of these vaccines?

"It doesn't do us much good to develop them if the public isn't interested in them," said Lawrence Stanberry, MD, PhD, director of the Sealy Center for Vaccine Development at the University of Texas Medical Branch in Galveston.

Dr. Stanberry is working on a herpes vaccine. Last year he and his colleagues reported the results of two large clinical trials in which the vaccine was found to be protective, but, surprisingly, only in women.

Physicians' acceptance of the vaccines is also a concern. Dr. Bernstein and his colleagues have been seeking funding for a physician survey on the HPV vaccine. "How likely are physicians to jump on the bandwagon?" he wondered. "Will pediatricians feel comfortable talking about sex? Same thing with OB doctors. They aren't used to giving vaccines."

Crossing a line

The new vaccines' focus on sexually transmitted diseases makes them different from many that have gone before. They push immunization well beyond a barrier that some believe was breached when the hepatitis B vaccine was approved in 1991.

Although hepatitis B can be a sexually transmitted disease, its potential spread via blood or saliva has allowed the vaccine's promoters to sidestep a discussion of sexual transmission.

"I think people have been able to separate hepatitis B from sex," said Dr. Bernstein.

But diseases being targeted by vaccines now in development are frankly sexual in nature. Some call them lifestyle or behavioral diseases. Barbara Loe Fisher, a frequent critic of vaccines and co-founder of the National Vaccine Information Center, fears that the approval of some of these new vaccines will inevitably lead to their being mandated for school admission. Hepatitis B vaccine is already required.

"It becomes a question of where does the state's right to try to control a disease or a disorder end and a parent's right to make a choice about a vaccine begin," she said. If any vaccines belong in an optional category, it is these new ones, she added.

Judy Converse, MPH, a nutritionist in private practice in Bourne, Mass., has looked closely at the effects of the hepatitis B vaccine on young children referred to her by physicians because of postvaccination developmental problems. She fears that the balance too often tips toward the assumption that something will go wrong if a vaccine isn't given. But, she argues, it is also important to ask what could go wrong if the vaccine is used. "What are the tolerable risks?"

Whether schools will ever require additional immunizations is anybody's guess. In the first round of the debate, public health officials will consider it a victory if the vaccines gain acceptance in general.

William Schaffner, MD, chair of the Dept. of Preventive Medicine at Vanderbilt University School of Medicine, Nashville, Tenn., sees the debate from a public health point of view that he believes is also realistic.

"We can't pick out with surety who will be exposed in the future at any given time," Dr. Schaffner said. "We can't go through a classroom and say, ah-ha, this is a person who will have many sex partners, or this is a person who will have no sex partners, or only one sex partner in their life.

"If we are going to protect a generation, then you begin to think that, although these diseases have to do with individually controlled behaviors, maybe we'd better vaccinate everybody. So the population approach to individual protection comes to the fore," he said.

To gain access to the teen population, several barriers must be overcome, noted Gregory Poland, MD, director of the Mayo Vaccine Research Group and professor of medicine and infectious diseases at Mayo Medical School in Rochester, Minn.

The first is to convince parents that their children will become sexually active at a time that cannot be pinpointed in advance and that the new vaccines likely will work only before someone becomes infected.

Dr. Poland and colleagues conducted a study of the HPV vaccine and found that 40% of the young women at a nearby college were already infected with the virus. Similar high infection rates are being reported throughout the country, leading to the conclusion that a younger, uninfected group is most in need of an HPV vaccine.

Another barrier is that the average person has no clue cervical cancer is caused by HPV, Dr. Poland said. "While cervical cancer is the second leading cause of cancer death in women, nonetheless, I would guess that not many women actually know someone who has died of cervical cancer. It's not real high on their radar screen, other than the piece where they know they should get a Pap smear at some interval."

Dr. Poland believes it will take a massive public education effort by physicians, insurers and others to achieve widespread acceptance of an HPV vaccine. Cost-effectiveness studies also will be necessary because the vaccine, which Merck & Co. Inc. has in phase III trials, is likely to be costly and require several doses.

As the debate on the vaccines' acceptance continues, researcher Gregory D. Zimet, PhD, professor of pediatrics and clinical psychology at Indiana University School of Medicine, Indianapolis, has been asking parents what they would do if vaccines for sexually transmitted diseases were available for their children.

To his surprise, the majority of parents surveyed said they would favor having their children vaccinated. For example, more than 70% of 34 parents interviewed in depth said they were willing to accept vaccines that target genital herpes, HIV, HPV and gonorrhea for their 8- to 17-year-old children. The study is planned for publication in an upcoming issue of Social Science and Medicine.

"Our thinking and other people's thinking has been that there might be resistance among parents to having their children, likely young adolescents, vaccinated against sexually transmitted infections," Dr. Zimet said.

Of course, he added, since the vaccines aren't available now, it remains to be seen if parents will be as accepting when the shots go on the market. Plus, he cautioned, the parents interviewed had accompanied their children to medical appointments. "So it's a group in which one would expect to see somewhat higher levels of acceptability in general because they are involved with their adolescents' health care."

Developing a shot schedule for teens

Getting adolescents into physicians' offices and clinics to receive the vaccines is recognized as a substantial barrier by most vaccine advocates. Teens don't generally show up in physicians' offices.

It was this concern that prompted Michael Decker, MD, MPH, vice president for scientific and medical affairs at Aventis Pasteur, to suggest that an influential federal committee begin to focus on adolescent immunizations.

When the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices was discussing the meningococcal vaccine and its use in teens, Dr. Decker urged the committee to broaden its scope. "I said I think you'd better start focusing on adolescents and thinking about what you are going to do because a number of the most important vaccines in the proximate pipeline, not only from Aventis but from our competitors, also are vaccines that really need to be given to adolescents."

Quite suddenly, the anticipated vaccines have generated a major need for an adolescent-focused immunization program, something that does not now exist, he said. Developing such a program will require that people think ahead and plan to address the problems that will arise.

"Every pediatrician, every practitioner, will tell you they see children when they are babies, they see them when the school makes them come for a school-mandated vaccine, they see them when they need a medical exam for sports or a job. Then they don't see them until the girls show up for birth control," Dr. Decker said.

In response, the advisory committee has designated a working group to examine issues surrounding the development of an HPV vaccine, said John Modlin, MD, ACIP chair and chair of the Dept. of Pediatrics at Dartmouth Medical School, Hanover, N.H.

The nation's experience with the rubella vaccine points to the difficulty the effort faces, Dr. Modlin said. That vaccine originally was intended to target teenagers but was never used alone in the United States as it was in some other countries. Here, it was given to infants, primarily because the acceptance rate was low among teens.

But Dr. Modlin suggested that the importance of the new vaccines could spur an adolescent vaccine visit. "I wouldn't be surprised if we aren't moving toward a more formalized adolescent immunization schedule with a visit or a series of visits because some of these vaccines may require more than one dose."

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