The usual highly paid drug company spokesperson - Dr. Gellin.
AMNews: Jan. 28, 2002. Vaccines can fail, but the reason may not be obvious
HEALTH & SCIENCE
Vaccines can fail, but the reason may not be obvious Determining why includes looking at the disease and the person as well as the immunization. By Susan J. Landers, AMNews staff. Jan. 28, 2002. Additional information Washington -- Vaccines are a wonder of modern medicine and have spared millions of people harm from such diseases as measles, polio, whooping cough and diphtheria.
However, sometimes vaccines fail to provide the reliable protection that many patients, especially the parents of young children, expect. A recent outbreak of chicken pox in Connecticut, for example, resulted in a flurry of phone calls that kept Vincent Sacco, director of the state's immunization program, busy for several days.
He was able to tell parents that the number and severity of cases did not appear to be out of the normal range. He also stressed that his state is far from the 100% immunization rate that would make such an outbreak unusual. Connecticut began requiring students entering preschool and kindergarten to be vaccinated against chicken pox in 2000, so many students are not yet immunized.
But outbreaks do occur, even among children already vaccinated.
Varicella vaccine is 85% effective.
"We don't always know the answer to why a vaccine fails," said Julia McMillan, MD, a professor of pediatrics at Johns Hopkins. "And chicken pox is probably the most problematic." She was quick to note that the varicella vaccine is still a very good vaccine, with an effectiveness rate at about 85%. And parents should be told that even if a child gets the chicken pox from a classmate or sibling after being immunized, the vaccine almost always protects them from "significant" infection, she said.
To really come to grips with why vaccines aren't 100% effective, "You have to look at the vaccine, the disease and the person," said Bruce Gellin, MD,executive director of the National Network for Immunization Information. Some people are more susceptible to a disease than others. "We don't always know why some people get sick and die while others may not be affected at all even though both may have been infected by the same organism," said Dr. Gellin, who is also an assistant professor in the Dept. of Preventive Medicine at Vanderbilt University, Nashville, Tenn.
Ongoing work in human genetics may provide some answers about the components of the immune system that are critical in responding to vaccines and more guidance on individual responses to vaccines, he noted. Care in handling But there are other intervening factors. Vaccines, for instance, could also fail to be effective if they are not stored at the proper temperature. The varicella vaccine has a very strict temperature requirement, Dr. Gellin pointed out. It must be stored frozen at -15 C, and it shouldn't be refrozen. Therefore, a vaccine can fail because of an unplugged refrigerator or the inattention of a delivery person.
Vaccines can lose effectiveness if not stored correctly.
The development of combination vaccines may bring other new problems. Such vaccines include those for measles, mumps and rubella, polio, diphtheria, pertussis and tetanus. Care must be taken to ensure that one vaccine doesn't interact with another to alter the immune response, said Dr. Gellin. Such interactions may be revealed after a vaccine has been used for some time. Dr. McMillan cites recent findings indicating that the immune response to the chicken pox vaccine appears to be diminished when it is administered within 30 days of the MMR vaccine.
The best time to administer the varicella vaccine is now thought to be either on the same day as the MMR vaccine or more than 30 days after the MMR vaccine is administered. The disease itself must also be examined when a vaccine fails to provide protection. "It is possible the organism is evading the immune protection the vaccine is delivering," said Dr. Gellin. The pneumococcal vaccine, for example, is designed to protect against 23 pneumococcal bacteria -- those thought to be most likely to cause disease in people. However, there are approximately 90 different types of pneumococcal bacteria.
Additional causes for vaccine failure include a person's age, weight, whether he or she smokes or whether they are male or female, he added. The hepatitis B vaccine, for example, had been administered in a patient's rump until it became apparent that it wasn't finding its way to the immune system of obese people. Now it's routinely given in the deltoid, said Dr. Gellin.
The fact that vaccines are not 100% effective can also cause disease outbreaks. While the measles vaccine is highly effective at 95%, said Dr. Gellin, that rate also means that one in 20 people walks away unprotected. When a pool of unprotected individuals comes together at a school, for example, an outbreak can occur. About 10 years ago such an outbreak did occur, Dr. Gellin pointed out.
Now the vaccine is administered in two doses with the goal of protecting those people who failed to be immunized at the first go-round. The technique appears to have worked. In the last couple of years, said Dr. Gellin, there have been fewer than 100 cases of measles. "We've gotten our community so protected that if a virus shows up it has no place to go."
Too many shots? Researchers say no
Washington -- Parents should be assured that the vaccines their children get are beneficial and are not overwhelming and weakening their immune systems, according to a paper published this month in Pediatrics. "Infants have an enormous capacity to respond to multiple vaccines as well as to the many other challenges present in the environment," according to the authors, who reviewed the recent literature on vaccines.
The paper should serve as a valuable resource for pediatricians, family physicians and other health professionals to use in addressing parents' concerns, said Jon Abramson, MD, chair of the American Academy of Pediatrics' Committee on Infectious Diseases.
Rather than overwhelming their immune systems, vaccines prevent the weakening of infants' immune systems by protecting them from a number of bacterial and viral pathogens, said the authors. Children in the United States now receive 11 vaccines that are administered in as many as 20 shots by the time they are 2 years old. The multiple shots had apparently led parents to question whether the process might actually be causing harm.
Responding to a survey conducted about a year ago, one in four parents of children younger than 6 said they thought too many vaccines could weaken their child's immune system, said Bruce Gellin, MD, an assistant professor at Vanderbilt University, Nashville, Tenn., who participated in the project. The new paper was written to address those concerns.
"We've had a tremendous impact on disease and we've done that by introducing new, effective and safe vaccines," he said. "Yet there is a perception that there might be some problem related to them. So we wanted to provide a scientific basis to give some kind of rebuttal to that concern."