There are several advantages to incorporating the new combination vaccines into the immunisation schedule.

There are several advantages to incorporating the new combination vaccines into the immunisation schedule.

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 brief discomfort children experience when given an injection, even 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.

New combination 1: MMRV

One of the 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 will be offered at 18 months of age, and replaces two shots that were previously given separately – the varicella vaccine at 18 months, and the second dose of the combination vaccine against measles, mumps and rubella vaccine (MMR) at four years.

The change means that at four years of age 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.

New combination 2: Hib-MenC vaccine

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.

This happened in 2011 and again in New South Wales 2012. Having the majority of the community immune to measles by receiving two doses of the vaccine is essential for preventing outbreaks.

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 this is not true.

Vaccines actually have the opposite effect, and actually 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, studies assessing immune responses to new vaccines 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.

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.

Kristine Macartney is an Associate Professor, Discipline of Paediatrics and Child Health at University of Sydney. Melina Georgousakis is a Senior Research Officer, National Centre for Immunisation Research and Surveillance at University of Sydney.

This article was first published on The Conversation