Combined diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated polio, and Haemophilus influenzae type b vaccine

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Infanrix hexa (GlaxoSmithKline)

0.5 mL in pre-filled syringe, with a vial containing 10 microgram Haemophilus influenzae type b vaccine

Approved indication: immunisation

Australian Medicines Handbook section 20.1

The development of new vaccines has increased the potential to prevent childhood illnesses. The expanded range of vaccines has, however, created the difficulty of children needing multiple injections at one time. Multivalent vaccines may help to overcome this problem.

These two products have been approved for primary immunisation at two, four and six months of age. They both contain the same antigens as the currently marketed Infanrix HepB, but also contain inactivated strains of polio virus. To prepare a hexavalent vaccination, the suspension of five vaccines is injected into a vial containing a pellet of haemophilus vaccine. The vaccines are then mixed until the pellet is dissolved and the resulting suspension is then drawn up for injection.

Three injections of the pentavalent vaccine, two months apart, produce an antibody response in more than 99% of babies. This response is as good as that seen when the vaccines are given separately. There is a similar response to the hexavalent vaccine, apart from a 96%response rate to the Haemophilus influenzae type b component.

Although the multivalent vaccines induce an immune response, limited information is available about their effectiveness at preventing infections. Their efficacy is considered to reflect that of their components. For example, the diphtheria, tetanus and acellular pertussis component is said to have an efficacy of 84% in protecting against whooping cough. Although the two products have been approved for use as boosters at 18 months, the current Australian Standard Vaccination Schedule does not include booster doses at that age.1

As with all vaccines, the health professional giving the intramuscular injection should be ready to deal with an anaphylactic reaction. Adverse reactions to these multivalent vaccines resemble those of their components. The most common reactions are pain at the injection site and irritability. Approximately 20% of children will develop fever.

The National Immunisation Program does not fund all the vaccines in the Schedule and the vaccines used vary between States.1 While these multivalent vaccines may help to simplify primary immunisation, protecting children against other diseases will still require multiple injections at 12 months of age.