WHAT ARE MULTICOMPONENT VACCINES?

• Multicomponent vaccines are vaccines which are specifically designed to protect against more than one disease with a single injection. They are not simply a mixture of different existing vaccines. Mulitcomponent vaccines are researched and tested in the same way as individual vaccines to ensure they are at least as effective and well tolerated as the individual vaccines would be.

WHY ARE MULTICOMPONENT VACCINES USED?

• Currently children need a minimum of 36 different doses of vaccine by the time they go to school to protect them against nine different diseases. Separating these would mean 36 individual injections.
• In many cases control of a particular disease has only been achieved once a combination vaccine has been introduced, as the rate of vaccine uptake necessary to control the spread of the diseases wasn't achieved with the individual components. Between 1970 (soon after the introduction of the single component measles vaccine) and 1988 there was an average of 13 measles deaths per year. However, these are now a rare occurance since the introduction of the combined measles, mumps and rubella vaccine.² Since 1992 all deaths have been in older people suffering the late effects of measles infection caught during the 1980s.³

• THERE ARE MANY BENEFITS OF USING MULTICOMPONENT VACCINES:
  • Fewer injections causes less pain and distress for children
  • Fewer visits to the doctor to complete the schedule, making it easier to ensure that no vaccines are missed
  • Children are protected against the maximum number of infectious diseases in the minimum amount of time
  • Increased vaccination coverage protects a greater number of individuals

HOW DO CHILDREN RESPOND TO MULTICOMPONENT VACCINES?

• The immune systems of children and infants can respond to large numbers of 'antigens' (anything which stimulates the immune system) at the same time. Research has estimated that an infant could respond to at least 10,000 vaccines (antigens) at once.⁴ This was calculated by looking at the capacity of the body to produce the cells and antibodies needed to produce an immune response. These cells and antibodies are continually renewed and in normal healthy people do not run out.
• A practical example of the body's ability to respond to a number of vaccines at once is how children show similar responses to a number of different vaccines given at the same time as to individual vaccines given at different times. If multiple vaccines overwhelmed the immune system then you would expect that multicomponent vaccines would not give the same level of protection as those given on their own. This is not the case, as a number of vaccines have been shown to give equal protection whether given on their own or in combination, e.g. MMR (measles, mumps and rubella) and DTP-Hib (diphtheria, tetanus, pertussis-Haemophilus influenzae type b[Hib]) vaccines.⁴

DO MULTICOMPONENT VACCINES CARRY A GREATER RISK OF SIDE EFFECTS?

• As with all vaccines, the risks associated with the vaccine are far outweighed by the risks due to the natural diseases they protect against.
• Studies have shown that multicomponent vaccines do not carry any greater risk of side effects than single vaccines. In groups given the Hib vaccine and a diphtheria, tetanus and pertussis vaccine (DTP) combined or separately, both groups showed:⁵
  • Similar immune response
  • Similar rates of local reactions (e.g. redness and swelling around the injection site) and general reactions (e.g. fever)

 

 

WHAT IS THE IMMUNE SYSTEM?

• Immunity is the body's way of recognising germs (bacteria and viruses) and fighting the infections they cause. Figure One illustrates the various parts of a child's body where the cells involved in producing an immune response are made: tonsils, lymph nodes and vessels (located throughout the body), thymus gland, bone marrow and the spleen.

Figure One - Places where immune cells are made

• Every day we come into contact with thousands of germs, although we rarely notice them because our immune system successfully deals with them. An example of your immune system at work would be the inflamed red throat you get when you have a cold.

HOW THE IMMUNE SYSTEM WORKS

• Germs can enter the body in a number of ways, for example through the mouth, nose or through cuts and grazes. Figure Two summarises how the immune system can fight germs which enter the body:

Figure Two - Overview of how the immune system can fight infection

Germs enter the body


The germs are either eliminated from the body,
preventing an infection OR begin multiplying, infecting healthy cells and causing an infection


If infection occurs, the body's 'immune system' produces antibodies (a type of protein)
and special white blood cells (lymphocytes) to attack the invaders


Antibodies attach themselves to the germs, making it easier for the white blood cells to identify them


White blood cells then attack and destroy the germs and infected cells

• The immune system also produces special, long-living 'memory' cells (types of white blood cell), which allow the immune system to recognise a germ it has seen before so that the body can mount a rapid attack and destroy it before any damage can occur.
• Anything that stimulates the immune system to produce antibodies is known as an 'antigen'. Immunity can be generated 'passively', 'naturally' or 'actively' via immunisation (see below for further information).

WHAT IS MEANT BY 'PASSIVE' IMMUNITY?

• A mother's own disease-fighting antibodies, present in her blood stream, pass to her unborn child during pregnancy. Mother's milk is also rich in antibodies and breastfeeding increases a baby's defence against infections (immunity). The immunity obtained in these ways helps to protect the baby immediately after birth. It is referred to as 'passive' immunity because the child's own immune system is not involved. Antibodies received passively in this way provide short-term protection to a newborn child although this 'inherited immunity' wears off in the first year of life, making it necessary for the child to generate his or her own immune response.

WHAT IS MEANT BY 'ACTIVE' IMMUNISATION?

• Active immunisation is the process by which an antigen is deliberately introduced to the body to stimulate an antibody response.
• Vaccines stimulate the body to produce antibodies in the same way as an infection, but without the danger of developing the disease and the resulting complications. When a vaccine against a particular disease, or group of diseases, is injected or swallowed the immune system reacts by producing antibodies that build up over time and protect against the particular disease that the vaccine is designed to protect against.⁶ This is known as 'active' immunisation.
• Vaccines can be made up of:
  • Killed bacteria
  • Weakened viruses or bacteria
  • Parts of the bacterium or virus
  • Inactivated (harmless) toxins
• All types of vaccine stimulate the body's own immune system to produce antibodies and cells in the same way as the disease would but without the dangers of the disease.

 

"There has been no good evidence that by making it a multiple vaccine, you have any different side effects than with a single vaccine." Dr David Elliman, St George's Hospital⁷

"Current studies do not support the hypothesis that multiple vaccines overwhelm, weaken or 'use up' the immune system." Dr Paul A Offit, Section of Infectious Diseases, Children's Hospital of Philadelphia⁴

Media coverage has highlighted parents' concerns about multiple vaccines.⁷ A recent telephone survey showed that although 87% of parents thought that vaccination plays an important part in keeping children healthy, 25% thought their children's immune system could be weakened as a result of too many immunisations.⁸

There are some key points to remember about multicomponent vaccines and the immune system:

• The immune response - At birth, a baby leaves the mother's womb, an environment relatively free of bacteria and viruses, and enters an environment with many bacteria and viruses. Within hours of birth a baby's nose, throat, skin and bowel will become inhabited by dozens of organisms without harm to the baby. Immune responses in the newborn, although not as efficient as an adult's, are able to meet the environmental challenges of birth.
• Children are exposed to many foreign antigens every day - Eating food introduces new bacteria into the body and many bacteria live in the mouth and nose, exposing the body to many antigens. A case of bacterial throat infection exposes a child to 25-50 antigens.⁹
• Vaccines are given at a young age to protect against diseases - While most children will recover from their infection and have no long-term complications, many infectious diseases are extremely severe and can lead to dangerous complications, or even death (e.g. whooping cough and meningococcal meningitis). Some of the most severe complications from infections are most common in the very young.
• Vaccines do not increase the risk of other infections - Vaccinated children are not more likely to develop infections than unvaccinated children, as would be expected if vaccines weakened the immune system. In contrast to increasing the risk of other infections, vaccines may actually reduce the risk, which has been shown in a number of studies, including:
  • A group of children who were vaccinated according to the childhood vaccine schedule (for diphtheria, whooping cough, tetanus and Haemophilus influenzae type b in a combination vaccine) by three months of age had fewer common symptoms from infectious disease, such as vomiting, coughing, runny nose, restlessness, rash and pain than a group of unvaccinated children over the same time period.¹⁰
  • Vaccination with the combined measles, mumps and rubella (MMR) vaccine did not increase the risk of hospitalisation from severe infection in the three months after vaccination. In addition, cases of pneumonia (severe life-threatening disease), septicaemia (blood poisoning) and meningitis were not increased in the period following MMR vaccination.¹¹
• Vaccinations do not weaken the immune system - Current studies do not support the theory that multicomponent vaccines overwhelm, weaken or 'use up' the immune system. The immune system has an enormous capacity to respond to multiple vaccines and the many other challenges present in the environment. By protecting against specific infectious diseases, vaccines prevent the weakening of the immune system and secondary infections which are caused by natural infection.⁴

 

 

• Following the introduction of vaccination there has been a dramatic decrease in childhood deaths and an increase in life expectancy.
• "Each year vaccines prevent up to three million deaths [worldwide] and 750,000 children are saved from disability" (GAVI 2001).
• Multicomponent vaccines allow children to be protected against more infections than ever before.
• Multicomponent vaccines do not overwhelm a healthy individual's immune system.

 

 

1. Global Alliance for Vaccines and Immunization (GAVI). Factsheet 169. Revised March 2001.
   

2. Immunisation against Infectious Disease TSO 1996.
   

3. Protecting the Population from infection - HPA/ measles deaths 1980-2002 http://www.hpa.org.uk/infections/topics_az/measles/data_death_age.htm
   

4. Offit PA, Quarles J, Gerber M, Hackett C, et al. Addressing parents' concerns: do multiple vaccines overwhelm or weaken the infant's immune system? Paediatrics 2002; 109: 124-9.
   

5. Bell F et al. Combined diphtheria, tetanus, pertussis and Haemophilus influenzae type b vaccines for primary immunisation. Archives of Disease in Childhood 1996;75:298-303.
   

6. European Vaccines Manufacturers - Immunisation Factsheet for Parents. http://www.evm-vaccines.org/ImmunisationFactSheetforParents.pdf
   

7. BBC Online; Reassurance over multiple jabs Nov 2002. http://news.bbc.co.uk/1/hi/health/2408555.stm
   

8. Gellin BG. Do parents understand immunizations. Pediatrics 2000;106 (5): 1097-1102.
   

9. Six common misconceptions about immunization. http://who.int/vaccines-diseases/safety/prof/misconcept.shtml
   

10. Otto S et al. General non-specific morbidity is reduced after vaccination within the third month of life-the Greifswald Study. J Infection 2000; 41:172-175.
    

11. Miller E et al Bacterial infections, immune overload, and MMR vaccine. Arch Dis Child2003;88: 222-223.