The introduction of the combined five-in-one vaccine is a welcome change to the childhood vaccination programme in the UK. This vaccine has been used widely throughout Europe and Canada for a number of years with excellent results in immunity and increased compliance. It is a pity that the department of health has taken so long to introduce it to the UK.

The current childhood vaccination schedule offers six separate vaccines to babies on each of three occasions in the early months of life: diphtheria, tetanus, pertussis (whooping cough), HiB (Haemophilus influenzae B), poliomyelitis and meningococcus C. Currently, this involves two separate injections on each occasion together with the administration of drops of polio vaccine through the child's mouth. The new vaccine will contain diphtheria, tetanus, pertussis, HiB together with a parenteral (injectable) form of polio.

There will still be the need to give a separate injection of the meningococcal vaccine as that has not yet been incorporated into a combined vaccine. Children will therefore receive two injections on each occasion, but there will be no oral administration of polio - so the number of vaccines given will remain the same.

The switch from an oral form of polio vaccine to the injectable form (which I and many other thousands of people had in the 1960s) is designed to decrease further the number of people experiencing polio within the UK. Apart from polio arising in immigrants who have caught the disease abroad, the only new polio cases that we are seeing are those resulting from the polio vaccine itself... When a child is immunised with oral polio, that child will excrete live polio virus in the nappy for some time: this could cause susceptible individuals to catch polio through poor hygiene. By switching to an injectable polio vaccine instead of the oral vaccine, we can maintain high levels of polio immunity while preventing the spread of oral-polio induced disease.

A secondary effect of the switch to the new five-in-one vaccine is that the constitution of the vaccine contains pertussis vaccine that is "acellular" rather than the current "whole cell" vaccine. Although UK statistics suggested that the acellular vaccine was slightly less effective in inducing long-term immunity, this has not been substantiated by other countries. A booster dose of acellular pertussis was recently introduced alongside boosters of diphtheria, tetanus and polio at the age of four years and this reinforcing dose will negate any possible decreased immunity from the acellular versus whole-cell vaccine. The acellular vaccine does not require thiomersal, a mercury derivative rapidly excreted by the body that has been the source of unsubstantiated complaints by a number of vaccination pressure groups who have postulated diseases linked to the use of thiomersal (less mercury is given to children through vaccinations than you would find in a small tin of tuna fish!). The use of this five-in-one vaccine will therefore reassure a majority of parents that thiomersal is no longer present.

In summary, the planned change to this five-in-one vaccine will not decrease or increase the number of vaccines given to any child, but will decrease the risk of vaccine-induced polio in those who care for young babies.

·Dr Nigel Higson is chairman of the primary care virology group and a GP in Hove, west Sussex