Abstract

With a combination vaccine that protects against five diseases now approved for use in the US—and other such vaccines on the horizon—pediatricians need answers to new questions: How should these vaccines be used for infants at various stages of immunization? Which vaccines can be used interchangeably? Is it safe to give extra doses? Administrative issues and parent education also need to be addressed.

Introduction

In 1960, routine childhood vaccination—with diphtheria-tetanus-pertussis (DTP), inactivated poliovirus (IPV), and smallpox vaccines—prevented five diseases and necessitated eight injections before the age of 2 years. Today, routine childhood vaccination prevents 11 diseases and requires as many as 20 injections—excluding influenza and hepatitis A vaccines—before the age of 2 years.^[1-3] (See the 2003 recommended childhood immunization schedule in the January issue of Contemporary Pediatrics.)

The increase in the number of vaccines, and the definitive success of those vaccines, has resulted in a remarkable decline in the incidence of the 11 targeted vaccine-preventable diseases in the United States (Table 1).^[4] But the growing number of vaccines also has created challenges. Keeping children's immunization status and records up to date may be daunting for health-care professionals and parents alike. Nurses, physicians, and parents may resist administering four or five injections to an infant at a well-child visit; some now even object to administrating more than two vaccines at a single visit.^[5-8] As a result, completion of vaccination may be delayed, possibly compromising protection, or families may be asked to make additional office visits solely for vaccinations, a policy that inconveniences families and is abjured by many insurance companies. What's more, many parents, unaware that the number of antigens in vaccines has dropped (Table 2), have become concerned by the number of injections: 23% of parents believe that the large number of immunizations children receive may have adverse consequences, and 25% believe that a child's immune system can be weakened as a result of too many immunizations.^[8]

In 1999, the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) stated that "the use of licensed combination vaccines is preferred over separate injections of their equivalent component vaccines" if an antigen in the combination is indicated and no antigen in it is contraindicated.^[9] Several licensed combination vaccines are already in use in the US. The vaccines against hepatitis B (Hep B) and Haemophilus influenzae type b (Hib); measles, mumps, and rubella (MMR); and diphtheria, tetanus, and acellular pertussis (DTaP) are commonly recognized as combination vaccines. Practitioners may overlook the fact that inactivated poliovirus vaccine contains protective antigens against three different poliovirus strains, and influenza vaccine is, likewise, trivalent.

Combination vaccines containing antigens that protect against five or six diseases are already in use in Canada, Mexico, and Europe. In December 2002, one such vaccine—DTaP-Hep B-IPV (Pediarix, GlaxoSmithKline Biologicals, Rixensart, Belgium)— received approval from the US Food and Drug Administration (www.fda.gov /bbs/topics/ANSWERS/2002/ANS01181.html). Another combination vaccine—DTaP-Hib-IPV (Pentacel, Aventis Pasteur, Swiftwater, Pa.)^[10]—is seeking FDA approval.

Although new combination vaccines have been eagerly awaited because they will decrease the number of injections infants receive, they also will raise questions about timing and scheduling, vaccine safety, record keeping, costs, and parent education.