Intended for healthcare professionals


Misconceptions about the new combination vaccine

BMJ 2004; 329 doi: (Published 19 August 2004) Cite this as: BMJ 2004;329:411
  1. Helen Bedford, lecturer in children's health (h.bedford{at},
  2. David Elliman, consultant in community child health
  1. Institute of Child Health and Great Ormond Street Hospital for Children, London WC1N 3JH
  2. Institute of Child Health and Great Ormond Street Hospital for Children, London WC1N 3JH

    Pentavalent vaccine is better in many ways

    The publicity surrounding the news of impending changes to the childhood vaccination programme has once again highlighted important misconceptions about combination vaccines. Although changes are being made to vaccines at three different ages,1 all the attention has focused on the new pentavalent vaccine (DTaP/Hib/IPV), being given in infancy, with headlines of chaos and panic. This is regrettable since the new vaccine offers children protection against the same five diseases as the previous regimen but in a slightly different, more acceptable, formulation. This change is a natural progression in the light of changes in the epidemiology of polio and advances in vaccine technology—developments that were predictable some years ago.

    The use of inactivated polio vaccine rather than oral polio vaccine is now possible because of the near elimination of polio worldwide. While wild polio remained a serious threat, the small risk of vaccine associated paralytic polio was outweighed by the superior community protection afforded. Oral polio vaccine is shed from the gut of an immunised individual, providing constant boosting to the community, whilst also preventing carriage of wild virus.2 These properties are no longer necessary because of the worldwide decrease in cases of polio. Many other European countries, as well as the United States and Canada, have already made this change. It has come later in the United Kingdom because the possibility of importation of polio from endemic areas has been greater owing to different patterns of migration.

    The second development is the use of a particular acellular or component pertussis vaccine rather than the current whole cell vaccine. The number of components in acellular vaccines in use varies from two to five. A three component acellular vaccine has been in use in the United Kingdom as part of the preschool booster since 2001. However, it is not sufficiently immunogenic for a primary course.3

    An as yet unpublished study has shown that the new vaccine Pediacel has the same safety and reactogenicity profile as the standard pentavalent vaccine used successfully in Canada for the past seven years (personal communication, N Kitchin, 2004). A trial in the United Kingdom, to be published later this year, shows that Pediacel produces notably fewer of the common, troublesome but minor side effects such as fever and soreness at the injection site than the current regimen (personal communication, E Miller, 2004). This should prove popular with parents who in one study said that they would prefer a vaccine that causes fewer reactions, even if this meant having an additional injection to offset this problem.4 Another advantage of the five component pertussis vaccine is that, unlike the three component vaccine, it can be mixed with Haemophilus influenzae type b (Hib) vaccine without reducing the immunogenicity of the latter.5

    Although research shows that thiomersal in vaccines is not associated with serious neurological problems,6 7 regulatory bodies have recommended its removal in accordance with the precautionary principle as long as this is not to the detriment of the vaccine programme.8 In any case it would not be possible to mix inactivated polio vaccine with a thiomersal product and still retain its immunogenicity.9 The new vaccines are all thiomersal free, and the whole routine childhood programme will therefore be without any mercury containing products.

    This is an important advance and generally well received in the United Kingdom, although some parent “advocacy” groups have expressed concern that this combined vaccine could overload the immune system. This is based on two misconceptions. One is that the immune system has a limited and relatively small capacity that is pushed to the limits by multiple vaccines. The other is that the increase in the number of diseases being protected against means an increase in the number of antigens. This vaccine has far fewer antigens than the DTwP/Hib it replaces. Because of the change from whole cell to acellular pertussis, a reduction of almost 3000 antigens has occurred,10 even though the vaccine protects against five instead of four diseases.

    Although this regimen will not increase the number of diseases covered by the programme, it represents an important step forward in the United Kingdom's vaccination programme. However, the benefits of the new vaccine do not outweigh the risks of delaying immunisation until its introduction. Such a delay would leave a child unnecessarily at risk of death and disability from whooping cough and Hib disease. Parents should therefore be encouraged to have their children immunised according to the current schedule, until the new one is introduced.


    • Competing interests HB and DE have in the past received funding from vaccine manufacturers Wyeth, Aventis Pasteur MSD, GlaxoSmithKline to attend symposiums and conduct research.


    1. 1.
    2. 2.
    3. 3.
    4. 4.
    5. 5.
    6. 6.
    7. 7.
    8. 8.
    9. 9.
    10. 10.
    View Abstract

    Log in

    Log in through your institution


    * For online subscription