Week 13: Microbiology- Immunisation
What are vaccines?
A vaccine contains a dead or weakened form of a germ that cannot cause the disease, but is enough to make the immune system produce antibodies to fight it. When a person is vaccinated, their immune system makes cells and antibodies in response to the vaccine, which will protect them from the real disease if they come into contact with it in the future Immunisation works in a similar way. Instead of the dangerous germ, vaccines are made of components of the germ that can't cause disease or from weakened versions of viruses. Through the delivery of a vaccine, the immune system is taught to respond to the harmless version of the germ so that it can respond quickly when faced with a real infection and stop us from getting sick. The vaccine doesn't cause the disease, but teaches the immune system to recognise the invaders in the future. Teaching the immune system how to respond to germs before we are exposed to them - gives us an advantage when we're faced with the real bug!
Is it safe to immunise children against so many diseases at the same time?
Babies and children come into contact with millions of viruses and bacteria every day from the moment they are born, and their immune systems are constantly responding to these. Combined vaccines such as measles, mumps and rubella (MMR) mean fewer visits to the doctor and fewer injections. Combined vaccines do not overload the immune system. Modern vaccines have fewer antigens (disease particles) than in previous decades, even though they protect against more diseases, because of improved manufacturing processes. When more than one vaccine is given in one visit, those vaccines have been tested to ensure that they are safe and effective to be given at the same time.
DTaP-IPV-HepB/Hib vaccine: doses
Badies need 3 doses of the vaccine: at 6 weeks old, 3 months old and 5 months old. Research has shown that the DTaP-IPV-HepB/Hib immunisation is very effective in protecting babies against the six diseases listed above. 80-95% of children who are immunised on time are protected against the diseases. It's important that your child has booster shots at 4 and 11 years old to make sure they remain protected.
What is pertussis?
Caused by Bordetella pertussis A childhood illness with paroxysms of coughing, whooping, apnoea, vomitting Typically lasts 6 weeks Importance of herd immunity: impacts disease incidence
Whole live organisms -e.g. -process -length of time
Coxpow, measles, mumps, rubella, BCG Establish infection in vaccinated person Immune responses clear infection after 1-2 weeks Prolonged exposure to organism Memory cells last long time, single dose usually effective at stimulating lifelong immunity
Prevention of smallpox
In the past: Inoculation of small amount of smallpox pus= variolation Innoculation of small amount of cowpox pus (which is similar to smallpox pus)= vaccination Cowpox protects against smallpox
Importance of herd immunity: example
Measles vaccination NZ had 2-3x greater cases of measles compared to US, with less children vaccinated
Vaccine efficacy
Most vaccines are extremely effective at preventing isease Often efficacy is >90%
Why are live vaccines pushed back?
Need to check that baby has healthy immune system IgG IgA: top up of mums antibodies
How do vaccines work? immune response
One of the immune system's primary functions is to identify and remove infectious organisms, thereby preventing disease. It does this by recognising molecular fragments of microbes, called antigens. Immunity can be achieved either actively, by exposure to the disease or vaccination, or passively via antibody transfer in utero and through breast milk, or by injecting serum that contains antibodies. The essential goal of active immunisation is to prime and prepare the immune system so that it can respond rapidly and specifically to the wild organism, thereby preventing (or attenuating) disease and, ideally, colonisation and infection. Administration of a vaccine elicits an immune response that begins with the innate, non-specific cells of the immune system recognising the vaccine antigens. The cells of the innate immune system then stimulate the cells of the adaptive immune system (T and B lymphocytes). Immune memory can last for many years, often for life. Protective levels of antibodies may wane, and a booster dose of vaccine can stimulate the memory cells into developing more antibodies. Vaccination with killed microbes or with fragments of the microbe commonly requires three or more successive doses over a period of some months to generate effective immune responses. In contrast, a single vaccination with a highly immunogenic vaccine, particularly a live attenuated vaccine, is usually sufficient to generate long-term immune memory. If a further dose (a booster) is given some months or years later, a greater and longer-lasting secondary response can be stimulated, reinforcing and extending the immunological memory for that microbe.
Should pregnant women be immunised?
Pregnant women can be immunised with inactive (non-live) vaccines. There is no evidence of a safety risk for the mother or her fetus. There is no need to delay pregnancy after receiving non-live/inactive vaccines, e.g. influenza, tetanus/diphtheria/pertussis, hepatitis B, human papillomavirus (HPV) vaccines.
What are some vaccine concerns of the public?
Should I vaccinate my child? Won't I harm them becuase too many vaccines might weaken/overwhelm the immune system?- look at the data
How safe are vaccines?
Strict procedures are followed when vaccines are made to ensure they are safe. Before a vaccine can be approved for use, it is trialled extensively, sometimes with tens of thousands of people. These clinical trials with volunteers can take several years. Throughout all of these processes, safety is monitored very closely. Before a vaccine is approved for use in New Zealand, the manufacturer must demonstrate its safety and effectiveness to the satisfaction of Medsafe, a division of the Ministry of Health. After a vaccine is introduced, its safety continues to be monitored for the duration of its use. The safety of vaccines is monitored internationally using many different methods.
What are some routine NZ childhood vaccines?
The National Immunisation Schedule recommends that children be immunised for protection from 12 preventable diseases before they are 5 years old, and 13 in total (including Human Papillomavirus at age 12). The diseases are: diphtheria tetanus whooping cough (pertussis) polio hepatitis B hib (Haemophilus influenzae type b) rotavirus pneumococcal disease measles mumps rubella chickenpox (varicella) - from 1 July 2017. Vaccines given: 1. DTaP-IPV-HepB/Hib vaccine: diphtheria, tetanus, pertussis, polio, hepatitis B, Haemophilus influenzae type b 2. Rotavirus vaccine 3. Pneumococcal vaccine 4. MMR vaccine: measles, mumps, rubella 5. Chickenpox (varicella) vaccine - from 1 July 2017.
What is small pox? symptoms
Universal infection, with no second attacks Fever, chills Rash which evolved over 3-4 weeks Caused 10% of all deaths in Europe 18th century Nowdays there is a near eradication of smallpox due to vaccines
Are there some children who shouldn't be immunised?
There are very few children who should not be immunised. However, if your child has had a serious reaction to a vaccine, is being treated for cancer or other severe illness, or has had a blood transfusion or other blood products in the last year, you should talk to your doctor, specialist or nurse before the immunisation. Children with asthma, allergies or who are recovering from an illness such as a common cold can still be immunised. Children with allergies, asthma, eczema and hay fever can have all the recommended immunisations unless they have a specific, severe allergic reaction, called anaphylaxis, to the vaccine or a component of the vaccine being offered. Vaccinators are trained to ask questions about any allergies that may exclude your child from being vaccinated. It is generally not recommended to delay immunisations. However, if your child has a fever above 38°C, the immunisation should be postponed so that vaccine responses, like fever, sleepiness or irritability, don't make it harder to work out if your child's illness is getting better or worse. If your child has an ordinary cough, cold, runny nose or another mild illness, but their temperature is normal or only slightly raised, they can receive their immunisations. An infant is born with an immune system that is capable of responding to immunisations but it does need training. Vaccines are recommended early in life in order to protect infants from developing dangerous diseases while they are most vulnerable.
reasons why vaccines are beneficial at: -individual level -population level -risks
Vaccines are given to people to protect them against disease. They provide not only individual protection for some diseases but also population-wide protection by reducing the incidence of diseases and preventing them spreading to vulnerable people. Some of these population-wide benefits only arise with high immunisation rates, depending on the infectiousness of the disease and the effectiveness of the vaccine Community immunity is an important part of protecting the community against disease. People who are immunised do not usually get sick from an illness they are vaccinated against, and can't pass the disease on to others. This prevents infection from circulating in the community and helps to protect people who are not immunised, those who are too young to be immunised and those who cannot receive a vaccine for some reason. Approximately 95% of the people in the community must be immunised to achieve community immunity against diseases such as measles. If 95% of children in the community are immune, then those who do not develop strong immunity or cannot be immunised have a smaller chance of becoming infected, because of community immunity.
What are the 3 different types of mechanisms of vaccines?
Whole live organisms- cow pox (cross-reactive), measles, mumps, rubella, BCG (attenuated)-stimulates immune system to produce immunological memory against TB Old way: Whole killed organisms (inactivated)- whooping cough (pertussis): Then we asked if we could find the particular antigen needed to make the antibody needed to get stimulation by and purify the antigen so we could only need the antigen. Components of organism (subunit): e.g. hepatitis B (HBsAg), tetanus toxid, haemophilus influenzae type B (hiB) capsule
Whole killed organism or components of organism
e.g. Pertussis, hep B, tetanus, Haemophilus influenzae Briefly expose vaccinated person to antigens of organisms Immune responses clear antigens within few days. Not a lot of memory cells generated- three or more doses usually required to stimulate lifelong immunity