The Promise of Combination Vaccines

The success of modern vaccines is one of the most extraordinary accomplishments of medical science. In earlier generations many children contracted communicable diseases, like polio and whooping cough, frequently with devastating consequences. Some children died; others were left with permanent impairments, perhaps dependent on a wheelchair. But the development of vaccines has made many of these childhood illnesses relatively rare and has thus improved the lifetime health and wellbeing of millions of people. Children have quite clearly benefited more from vaccines than from any other preventive public health program in history!

Unfortunately, some parents have become complacent about their children’s immunisations. They have mistakenly presumed that these serious diseases have disappeared or have been eradicated.

We have become victims of our own success. George Santayana (1863-1952) said, “Those who cannot remember the past are condemned to repeat it”.

A few parents have been frightened away by reports of possible side effects associated with certain vaccines. However, the risks of not receiving immunisations are immense. As a responsible parent, you need to ensure that your child receives all of the currently recommended vaccines. Today’s vaccines are safe and generally produce only mild side effects (such as fever or localized redness). Severe adverse reactions are extremely rare.

When your child is given a vaccine, he actually receives that part of the “weakened” or infectious organism that has been killed but is still able to stimulate his body to produce antibodies. These antibodies then protect him against the disease, should he ever come in contact with it. This protection is virtually life long!

For maximum effectiveness and protection, immunisations should be administered at particular ages.Your child should receive most of his childhood immunisations before his second birthday. These will protect him against 10 major diseases: tuberculosis, polio, measles, mumps, rubella (German measles), pertussis (whooping cough), diphtheria, tetanus, diseases caused by Haemophilus influenza (Hib) and hepatitis B. Immunisations are also available against a host of other communicable diseases including chicken pox, diarrhoea, influenza, rabies, meningococcal meningitis, pneumococcal infection and hepatitis A.

Children currently receive the following shots before they enter school, including:

• 3 doses of Hepatitis B
• 1 dose of tuberculosis
• 5 doses of DTwP (diphtheria, tetanus, whole cell pertussis) or DTaP (acellular pertussis available from the private sector)
• 3 – 4 doses of Hib
• 5 doses of IPV or OPV (Inactivated polio vaccine or Oral polio vaccine)
• 2 doses of MMR (measles, mumps, rubella)

They may also get a chicken pox shot after age 1 year, an annual influenza shot and 2 shots of Hepatitis A as an option. Every parent and paediatrician would like their kids to get less shots. However, there are only a few ways for this to happen:

• You could choose not to vaccinate your kids and put them at risk of vaccine preventable illnesses. This is not an option for most parents, given the seriousness of the diseases and the permanent sequelae that could occur if your child fell sick.
• You could hope that vaccine preventable diseases will be totally eliminated worldwide, so that the vaccine isn’t needed any more. This has already happened for smallpox. The last naturally acquired case of smallpox was a Somali cook on 26 Oct 1977. The next likely candidate for global eradication is poliomyelitis, which the WHO targets for 2005. The eradication of other illnesses (such as measles) is still so far off that there are no real target dates set for them as yet.
• A more realistic, safe and effective option would be to request for combination vaccines to decrease the number of shots your child gets. The Ministry of Health currently recommends 10 vaccines for routine use in all children as enumerated earlier. Of those 10 vaccines, six are given in combination. The diphtheria, tetanus and pertussis vaccines are combined to make DTwP. And the measles, mumps and rubella vaccines are combined to make MMR.

Very careful studies have been designed to evaluate these combination vaccines. Before a combination vaccine can be licensed for general use, it has to be tested to check:

1. How effective is it? Does it stimulate the child’s immune system to produce protective levels of antibodies to all the diseases being immunised against?
2. How safe is it? Are there any side effects due to the combination?

With the DTwP and MMR combinations, it has been conclusively shown that the combination vaccines are as effective and as safe as when given individually.

However, the recent introduction of new vaccines (such as Hib, acellular pertussis, varicella and IPV) has raised some pertinent questions about the effectiveness of some combination vaccines. These are all excellent vaccines on their own right.

The Hib or “meningitis vaccine” has dramatically reduced the chances of acquiring Haemophilus influenzae B which causes inflammation of the lining of the brain (meningitis), blood stream infection and pneumonia. The varicella or “chicken pox vaccine” is gradually attaining widespread acceptance because the benefits clearly outweigh the risk of the disease. Unlike the whole cell pertussis (wP) vaccine, the acellular pertussis (aP) works equally well with the added advantage of causing less adverse effects. The OPV is an excellent vaccine against polio but has a 1-in-a-million probability of causing the disease. With IPV, this adverse reaction is zero.

Combining these excellent new vaccines in a single syringe has been a bit more problematic compared to the conventional DTwP and MMR. It is not as simple as drawing the different vaccines into a single syringe and administering it as a single shot. That is why your doctor cannot just mix the shots together.

A lot of research has to go into making sure that the combination shots are safe and they work well. Sometimes, various components of the new vaccine may interfere with the ability of a particular vaccine to induce immunity and hence protection. The interfering portion may be the stabilizer or buffer or even the vaccine itself. For reasons that still remain unclear, it has proven surprisingly difficult to combine a DTaP vaccine with an Hib vaccine without impairing the immunogenicity (effectiveness) of the Hib vaccine.

In his choice of vaccines, your doctor would have considered all these intricacies and selected the combination that would ensure your child’s protection from the target diseases are not compromised.