Dr Phil Kieran: Do my boys need to get their polio vaccine again? 

Poliomyelitis or polio is an illness that most of us have heard about but thankfully none of us has seen. This is due to huge efforts worldwide to vaccinate and eradicate polio which means we should never again see images like those of dozens of children in ventilation chambers (iron lungs) in polio wards.

Polio is a virus that mainly affects children under the age of five and, in nine out of 10 cases, causes mild illness. However, one in 10 children infected will become quite unwell, one in 200 will suffer some degree of paralysis, usually permanent, and one in 1,000 infected children will die.

Polio has no treatment so prevention with the vaccine is our only control. Until recently, polio was significantly present in just three countries worldwide — Pakistan, Afghanistan and Nigeria. However, in the news, you will have seen talk of outbreaks in the USA and Britain.

Mostly these outbreaks are where infectious polio virus has been found in sewage surveillance, although there has been one case of paralysis in the USA. These outbreaks happen when an unvaccinated population gives viruses a reservoir to spread. In a lot of countries, an oral live polio vaccine is used, which gives people a weakened form of the virus, allowing their immune system to produce antibodies without the risk of illness. However, the weakened virus can be present in faeces after a live vaccine like this. If a significant group of people are not vaccinated, particularly if there can be sewage contamination of drinking water, the virus can spread and mutate. If the unvaccinated population is large enough, the virus can undergo sufficient mutations to cause illness again potentially.

So, who needs to be worried about this? Firstly, anyone who has never been vaccinated against polio should get vaccinated. If 95% or more of the population is vaccinated, it is unlikely for the virus to spread and mutate (this is how vaccination protects you and all those around you). If you are travelling to a country with high levels of polio, talk to your doctor at least a month before you go so they can advise/arrange any boosters that may be necessary. In Britain and the USA, they have started a booster programme for children under five in high-risk areas (London and parts of New York).

At the moment in Ireland, there is no or very low risk of being exposed, but if we start to have more people declining childhood vaccines, that statement will become less accurate.

• If you have a question for GP Phil Kieran, please send it to parenting@examiner.ie