Changes to the National Immunisation Program schedule coming into effect today (July 1, 2013) will see two fewer injections given to young children. The changes represent a more efficient way of delivering protection against disease through the use of new combination vaccines.
This is good news for parents and carers (and incidentally, health-care providers) who don’t relish the transient discomfort children experience when given an injection, despite knowing the importance of immunisation.
Children will still be protected against 16 diseases through the national program, but fewer injections will be needed because of two relatively new combination vaccines replacing four previously recommended ones.
The new combination vaccines
One of these new combination vaccines is called MMRV and provides protection against measles, mumps, rubella and varicella (chickenpox). Protection against measles, mumps and rubella requires two shots, while chickenpox requires only one shot for children.
The MMRV vaccine (to be offered at 18 months of age) replaces two shots that were previously given separately – the varicella vaccine that was already at 18 months of age and the second dose of the combination vaccine against measles, mumps and rubella vaccine (MMR) that was given to four-year-olds.
The change means that, at four years of age – when they’re a lot more aware of how many plasters they’re sporting – children will only be given one injection (the diphtheria-tetanus-pertussis-polio booster, known as DTPa-IPV vaccine). The first dose of MMR will still be given at the age of one.
The second of the new combination vaccines (the Hib-MenC vaccine) replaces two vaccines also recommended at the time of a baby’s first birthday – the vaccine for haemophilus influenza type b (Hib) and the one for meningococcal C (both bacteria cause meningitis, septicaemia and other serious infections).
The Hib-MenC vaccine provides protection against both diseases with one injection, which means, at 12 months of age, two rather than three injections are needed for most children (you’ll recall the other one is the first dose of the MMR vaccine).
The benefits of combining
The obvious benefit of combination vaccines is that they provide protection against the same number of diseases with fewer injections. But there are other advantages to incorporating the new combination vaccines into the immunisation schedule.
Adding the MMRV vaccine to those given at 18 months means that children will now receive the second dose of their measles vaccine two-and-half years earlier. Although Australia is free from measles circulating in the community, large outbreaks can occur when travellers reintroduce the virus, particularly into pockets of the population where there is sub-optimal vaccine coverage.
The use of MMRV at 18 months is also expected to improve protection against chickenpox. Previously, this vaccine was the only one given at 18 months, and was sometimes forgotten. As a result, coverage against chickenpox has been lower than for other childhood vaccines, with around 84% of children immunised by the age of two.
Chickenpox vaccine was only introduced in 2005, and there has already been a 75% reduction in hospitalisations for chickenpox in children younger than five years old. We can expect further benefits with the increase in the number of vaccinated children.
This change should also see more children get the second dose of the MMR vaccine in a timely way than when it was recommended at the age of four.
Similarly, the convenience of the combination Hib-MenC vaccine at 12 months, rather than two separate injections, will no doubt contribute to more children being vaccinated. This should maintain or improve upon the low rates of both diseases that we have already seen since these vaccines were included on the national immunisation program over a decade ago.
The immune system and combination vaccines
The role of the immune system is to survey all the foreign particles (often referred to as antigens) that you come into contact with and, if necessary, make an immune response to them.
There’s a common myth that vaccines, particularly combination vaccines, overwhelm or weaken a child’s immune system. But like all myths, this is not true.
Vaccines actually have the opposite effect, and work to strengthen the immune system, as they stimulate it to recognise and protect against a virus (or other antigen) whenever the body comes in contact with it in the future.
Importantly, the amount of virus antigen in a vaccine is much less than the amount you would naturally encounter and it is modified to give an immune response which protects, but without making you sick (which is what the natural infection does). To be sure that combination vaccines have no untoward effects, vaccines studies assessing immune responses to new vacines and others routinely used at the same time are carried out before a vaccine is registered for use.
Clinical studies comparing MMRV on its own, with MMR and chickenpox vaccines given at the same time at different sites, have found that the immune response to all four viruses is similar.
Combination vaccines have successfully been used in Australia for many years to protect against multiple diseases with only one injection. We have been using the six-in-one vaccine recommended at two, four and six months of age since 2005. This vaccine protects against diphtheria, tetanus, pertussis (whooping cough), polio, Hib disease and hepatitis B.
Although vaccines against these diseases had been in use for many years prior to 2005, having a six-in-one vaccine has made immunising easier for all.
Benefits outweigh risks
Part of the decision-making process around the introduction of new vaccines is the assessment of the benefit and risks of vaccination.
Recall that the measles, mumps, rubella vaccine has to be given in two shots. Clinical trial and post-marketing surveillance data have identified a small increased risk of fever, and in turn, a small added risk of febrile seizures in children when the MMRV vaccine is given as the first dose of the MMR-containing vaccine, compared to when the MMR (with or without chickenpox vaccine at the same time in another injection) is given.
This risk of fever is greatly reduced when the MMRV vaccine is used as the second dose of the MMR-containing vaccine. This is why MMRV is to be given at 18 months of age after just MMR as the first vaccine dose.
Vaccine safety is continually monitored after a new vaccine is introduced into the population. This occurs through passive national surveillance mechanisms such the Therapeutic Goods Administration’s Adverse Drug Reaction Reporting System, as well as smaller specific active surveillance systems like the Paediatric Active Enhanced Disease Surveillance.
You can rest assured that the changes to the national immunisation program result from a close examination of what we have been doing and ways to improve it. The changes provide children with greater protection while giving them fewer shots.