Combination vaccines and multiple vaccinations

Over the last 50 years there has been a big increase in the number of vaccines given to children. If all these vaccines were given separately, each child would have to receive a large number of injections. Combination vaccines such as the 6-in-1 and the MMR have been developed to help reduce the number of injections needed. Even so, babies and children often receive several vaccines at once. For example, in the UK a 2-month-old baby will receive the 6-in-1, PCV, Rotavirus and MenB vaccines at the same time.

Parents sometimes worry that their child’s immune system will not be able to cope with receiving several vaccines at once. In fact, even a tiny baby’s immune system can cope easily. From birth onwards, a baby comes into contact with millions of germs every day. Babies' immune systems are working all the time to protect them against bacteria and viruses in the environment. Vaccines represent a very small challenge to the immune system when compared to this. Each millilitre of blood contains ten million B cells, the white blood cells that are associated with the immune response.

It is estimated that this would be enough to cope with thousands of vaccines at a time, meaning that a baby’s immune system is not stretched at all by receiving several vaccines at once. It is not a good idea to delay vaccinations to ‘spread the load’, because it leaves the baby unprotected against dangerous diseases for longer.

Although the number of vaccines has increased, the number of antigens in vaccines has actually gone down dramatically. Antigens are the active ingredient in vaccines, the parts made from viruses or bacteria which challenge the immune system so that it makes antibodies to fight the disease. In 1960 there were around 3200 antigens in components of vaccines that protected babies and children against just four diseases. By 2012, vaccines for babies and children contained just over 60 antigens but protected against 11 diseases.

Several studies have looked at the safety of giving children more than one vaccine at the same time:

• A European study published in 2013 assessed the MenB vaccine when given alongside the 6-in-1 vaccine, a pneumococcal vaccine and a MenC vaccine. The study found that giving the MenB vaccine together with other vaccines did increase the risk of fever and local tenderness at the injection sites. However there was no effect on the vaccines’ ability to stimulate an immune response.
• A UK study from 2011 looked at the safety of giving the MMR vaccine, the Hib/MenC vaccine, and the 7-valent PCV (pneumococcal vaccine) to 12-13-month-old babies. This was before the MenB vaccine was introduced, and the UK has also now changed to the 13-valent PCV. In summary, this research found no difference in side effects or immune response when these three vaccines were given separately or together.
• Addressing Parents’ Concerns: do multiple vaccines overwhelm or weaken the infant’s immune system?  is a review from 2002 of the effect of multiple vaccines on the child's immune system.

A study published in 2018  provides more evidence that multiple vaccines do not weaken the immune system. The researchers compared two groups of children. In one group the children had been hospitalised with infections that cannot be vaccinated against (such as many chest infections and stomach upsets). In the other group, none of the children had been hospitalised with these sorts of infections. The researchers then looked at how many vaccines the children in each group had been exposed to, and found no significant difference. (If vaccines did weaken the immune system, you would expect to find that the children hospitalised with infections had received more vaccines that the ones who were not hospitalised.)

Other studies have found no evidence that childhood vaccination is linked to an increased risk of developing type 1 diabetes or conditions such as multiple sclerosis . Researchers have also found no evidence that vaccination will trigger allergies. Allergy UK states that ‘All available information about immunisation and allergy points to the fact that immunisation in children who are at high risk of developing allergy is safe and not a factor in their future allergic conditions' (see the Immunisation Factsheet available to download on the Allergy UK website).

In the short film below, Professor Sophie Hambleton talks about the safety of combination vaccines.