In an exclusive interview, James Cherry, MD, told us that increased use of acellular pertussis vaccines may allow boosters later in life.
NEW YORK Pertussis as we know it will never be the same, predicted James Cherry, MD, professor of pediatrics at the University of California Los Angeles School of Medicine.
"I am hopeful we can eventually eradicate pertussis," said Cherry, a leading researcher in the field of pertussis. Cherry spoke exclusively to Infectious Diseases in Children about his thoughts on acellular pertussis vaccines and their impact.
Without the 15-month booster dose, the multicomponent acellular vaccines tested in Sweden and Italy were effective for 17 months to 20 months after the third dose (see Infectious Diseases In Children 1995; 8(11):11-18). Protection conferred by the whole-cell vaccine, however, did wane without the booster.
"Some of the new vaccines may give longer protection," Cherry said. "We may be able to eliminate one dose in infancy or perhaps the dose currently given in the second year of life. A fourth dose could be given at school entry and a fifth dose about 10 years later."
This ability to give booster doses later in life may be an important advantage of the acellular vaccines.
Immunity to pertussis, both vaccine-induced and natural, wanes over time, leaving adults susceptible to reinfection and, therefore, a source of infection for children. Because reactions are thought to be more severe in older children and adults, whole-cell pertussis vaccines are not recommended for anyone older than 7 years.
Acellular vaccines contain only specific proteins and may thus be less reactogenic in adults, as they are in children (see sidebar). Clinical trials assessing the safety and efficacy of acellular vaccines among adults are in progress, Cherry said.
Having a safe and effective pertussis vaccine licensed for adult use, however, is only half the battle of eliminating any vaccine-preventable disease. No matter how effective the vaccine, it is useless unless it reaches the intended recipient.
"Getting the vaccine into adults is the challenge," Cherry said. He cited the low coverage rates among adults for influenza, pneumococcal and hepatitis B vaccines as examples of the difficulty of immunizing adults.
Another problem is that many physicians do not realize how widespread pertussis is outside the pediatric population.
"Pertussis is not diagnosed in adults. Physicians do not look for it. There is a question of whether individual physicians would recognize pertussis in adults," Cherry said.
The only way to control spread of the organism the epidemiology of Bordetella pertussis is to vaccinate adults and eliminate that reservoir. This is a Catch-22 situation, however, because adults are not recommended for vaccination with current vaccines.
"Vaccinating children has not affected the circulation" of B. pertussis outbreaks of disease continue to occur in two- to five-year cycles, Cherry said. "But this can be changed."
The disease may be well controlled, however, in the absence of adult booster doses.
"Pertussis can be controlled in children if they are all vaccinated, with the occasional odd case," Cherry said. "We can control the disease without controlling the spread of the organism."
Despite the high hopes for acellular pertussis vaccines, their debut may be subdued. The first diphtheria-tetanus-acellular pertussis products that are licensed will not be combined with Haemophilus influenzae type b. This means an additional injection. Another drawback may be the price, which is expected to be higher than for whole-cell pertussis vaccines.
"There will be no place for the whole-cell vaccine in the United States. It may be used for a time in developing countries, where cost may be a problem," Cherry said.
"Price could be an issue in the United States, too, especially at first. But when the [Advisory Committee on Immunization Practices] and the [American Academy of Pediatrics] recommended acellular vaccine for the fourth and fifth doses, it cut down the number of emergency room visits" for treatment of adverse reactions. If a similar reduction in hospital visits is seen after the licensure of acellular vaccines for the first three doses, it would represent a long-term savings.
"Price is an important issue," he continued. "Many things are not controlled by physicians. They may have a situation where acellular vaccines are not available to a large group, such as members of a certain [health maintenance organization]."
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