Vaccines

How do they work? Who needs them? Are there any risks?

Vaccinations are one of the best ways to protect against many serious diseases.

How do vaccines work?

Vaccines prevent diseases. They work by making your immune system produce special cells called antibodies that will attack and kill diseases when they enter the body.

This means that if a person is infected with a disease (from a cough, sneeze, blood, etc), these protective antibodies are already in their bloodstream to quickly fight off the germs. Even if vaccinated people do get sick from the disease, they will usually get a mild form of that disease – and will recover faster and be less likely to have serious complications.

Babies are born with immunity to some infections because their mother’s antibodies are passed on to them in the womb, but this immunity does not last long. Babies get more immunity from being breastfed and, as they grow, they need vaccinations at specific ages to protect them from many life-threatening diseases. Read more about vaccine-preventable diseases.

(Ministry of Health NZ, 2017)

What are the types of vaccines?

There are generally 3 types of vaccines.

Type of vaccine Description
Live vaccines
  • These contain bacteria or viruses that have been weakened so that they cannot cause disease. 
  • After immunisation, the weakened vaccine viruses or bacteria replicate (grow) in the vaccinated person. This small amount of virus or bacteria can stimulate an immune response.
  • Examples of these vaccines include:
    • measles, mumps and rubella vaccine (MMR)
    • rotavirus vaccine
    • chickenpox vaccine. 
  • Live vaccines are not recommended if you are pregnant or have a very weak immune system from active cancer, leukaemia, lymphoma, HIV or taking medicines that can weaken your immune system. 
Dead (or inactivated) vaccines 
  • These contain bacteria or viruses that have been killed or inactivated. 
  • They can be safely given to a person with a weakened immune system. However, a person with an impaired immune system response may not develop the same amount of protection after immunisation as a healthy person receiving the vaccine.
  • With inactivated vaccines, you usually need many doses to give full protection against diseases.
  • Examples of these vaccines include:
    • polio vaccine
    • some influenza vaccines
    • hepatitis A vaccine.
Subunit vaccines
  • These contain parts of bacteria or viruses or bacterial toxins that have been made harmless. 
  • Examples of these vaccines include:
    • diphtheria vaccine
    • tetanus vaccine
    • hepatitis B vaccine
    • human papillomavirus (HPV) vaccine
    • Haemophilus influenzae type b vaccine
    • meningococcal vaccine
    • pneumococcal vaccines. 

Vaccines may also contain other ingredients, such as preservatives, and ingredients that help the body respond to the vaccine. The very small amount of these ingredients do not cause any harm.

When should you get vaccinated?

The National Immunisation Schedule has a list of free vaccinations for different ages. Vaccinating on time gives the best protection. Missing or late vaccinations can put your family’s health at risk. 

Most vaccines are given to babies and children to build up their immunity. Vaccination starts at 6 weeks old. Other vaccines are recommended for people who are at greater risk of certain diseases, such as people with a weakened immune system because of illness or the medicines they are taking, the elderly or people who are travelling overseas where certain diseases are more common.

Are there any risks to being vaccinated?

Most reactions to vaccines are mild, such as fever or redness at the injection site. These reactions show that the immune response is building and the vaccine is working. Very rarely, a serious allergic reaction (anaphylaxis) can happen. This is treatable and occurs soon after the injection. This is why you must wait at the doctor's clinic for 20 minutes after vaccination. If you are worried, contact your doctor straight away. Read more about comparison of possible disease complications and vaccine responses

How effective are vaccines?

Studies have shown that if all recommended doses of vaccines are given, they will protect 80–98% of the children who are vaccinated. For example, pertussis (whooping cough) vaccine is effective in about 84% of children and the measles vaccine in 90–98% of children.1

Vaccination is an important part of protecting the community against disease. This helps to lower serious infections spreading and protects babies who are yet to be fully vaccinated and people who cannot be vaccinated because they are unwell. About 95% of people in the community need to be vaccinated to protect the whole community against diseases like measles.

A very small number of children who are vaccinated do not develop strong immunity and they may still become ill with one of the diseases. If that happens, they usually have a milder illness than people who have not been vaccinated. More than one dose of some vaccines is needed for full protection. Booster doses of vaccines may be also be needed for some diseases to stay protected.    

Learn more

Immunisation overview Immunisation Advisory Centre, NZ 
How vaccinations work NHS Choices, UK
Diseases and vaccines Ministry of Health, NZ
Vaccine administration Immunisation Advisory Centre, NZ

References

  1. Childhood immunisation HealthEd, New Zealand
  2. Types of vaccines Immunisation Advisory Centre
Credits: Health Navigator Editorial Team . Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 13 Dec 2017