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Combination vaccines simplify and speed up the administration of antigens

By Michelle Ciriacruz

With the use of combination vaccines, immunizing against vaccine preventable diseases becomes so much simpler. It has great practical value. There are fewer injections for patients to be distressed about. The medical staff saves on time since administration of vaccines is simplified and speeded up, and the public health system benefits from a simplified vaccination calendar.

    All of these result in better compliance, when parents and other adults have fewer important shots to be forgetful about. More people, especially children, are therefore vaccinated with the antigens that would boost their immunity against infections.

    Pediatric Infectious Disease expert Dr. Lulu Bravo points out: "The most important is improving the coverage." With three or four vaccines in one go, she explains that the possibility of missed opportunities for immunization is diminished.

    The use of combination vaccines is not new. The trivalent influenza vaccine being administered since 1945 is already very familiar. In 1948, the DTP (diphtheria, tetanus, and pertussis) combination was introduced in the United States. The trivalent inactivated polio vaccine (IPV) was launched in 1955; then in 1963, the trivalent oral polio vaccine (OPV) started to be used routinely. The triple MMR (mumps, measles, and rubella) vaccine was not introduced until 1971.

    The trend today seems to be the combination of as many vaccines in one injection or addition of as many antigens in one syringe as possible, to reduce the frequency and number of injections.

    The latest has nine antigens that give active immunization against six diseases-polio (Mahoney, MEF 1, and Saukett strains), diphtheria, tetanus, hepatitis B (recombinant), pertussis, and Haemophilus influenzae type b-manufactured by Aventis Pasteur.

    According to Dr. Luc Hessel, executive medical director of Aventis Pasteur-MSD, beyond the simplicity and convenience offered by the use of combination vaccines, the health economic value is also a big plus.

    He explained that it is more cost-effective than multiple vaccines, and it also allows for less medical intervention.

    The savings, explained experts, result from the fewer injections and greater immunization coverage that would be had if combined vaccines were to be incorporated into current delivery schedules.

    A case study of combination vaccines performed by Susan McKinley and Julie Milsten (World Health Organization document, www.who.int/vaccines/meetings/sage2002/documents/innovation/in2.doc), cites other benefits.

    Since fewer syringes are used with combination vaccines, vaccine-related waste is lessened. Exposure to thimerosal, a mercury-containing compound, is also reduced. Benefits also include the ease of adding a new antigen and possible cost savings over time.

    With advantages come drawbacks or complications, however. The study cited these major issues on the use of combination vaccines. These are financial sustainability, impact on the supply of traditional vaccines, how it will fit with the different immunization recommendations, regulatory issues, and acceptability.

    The interference between antigens should also be looked into. Of course, the efficacy and safety are major concerns. With each component added, a combination vaccine, in effect, becomes a new product with qualities that should be tested thoroughly before it becomes acceptable for public use.

    With all the possibilities posed by the use of combination vaccines, there is now no turning back from this question: Are we in a position to incorporate new combination vaccines into national immunization programs?

    Dr. Hessel explains that it is not a matter of adopting the program to the antigens, but a matter of adding the antigens to the program.

    Dr. Bravo concurs: "If you are able to know beforehand thep previous injections they have had, we can modify the immunization schedule depending on which immunization has been given before...What you really need to know is how many doses are still needed."

    She relates that when infectious disease experts and pediatricians conducted a study among the pediatric patients at the Philippine General Hospital, Research Institute of Tropical Medicine, and other medical centers on the efficacy and safety profile of combination vaccines, they came up with very good results.

    Dr. Bravo says that besides helping the doctors become more confident in the use of combination vaccines, the study showed that the combination vaccine induced a satisfactory immunogenicity and a lack of reactogenicity among the Filipino children. They also established that the use of combination vaccines would not interfere with the efficacy of other vaccines.

    In a related interview, Dr. Bravo disclosed that one of the major projects of the Philippine Foundation for Vaccination is to promote immunization among college students, particularly with these vaccines: hepatitis A, hepatitis B, chicken pox, DT, and MMR.

    She says the use of combination will not only simplify the immunization program but also make it more affordable for the students and the schools. She explains that hepatitis A is more expensive if given separately than if in combination with hepatitis B.

    Meanwhile, Dr. May Book-Montellano, a professor of pediatrics at the Far Eastern University-Nicanor Reyes Memorial Foundation Institute of Medicine, acknowledges the big gap between developing and developed countries in the use of combinations vaccines. Affordability is really the main issue, however, she points out that less developed countries have already incorporated combination vaccines in their routine immunization programs-as they were able to realize the rationale behind this system of delivering several antigens in one go.

    Dr. Montellano explains that with the influx of vaccines being developed and licensed, the only way to go forward is to take advantage: "So we can enhance or effectively utilize the immunization against these [vaccine] preventable diseases."

    There would thus be fewer needless deaths and sickness from diseases we already have the armamentarium to fight with, but because of varied reasons, did not make use of.