Immigrants to Ireland have been warned that they may be putting both themselves and their children at risk of serious infectious diseases when they travel back to their home countries.
The need to get vaccinated against a range of diseases to which they were previously immune is stressed in a new booklet now available free of charge in GP surgeries.
Those who are most at risk are those who come from tropical countries and who have been living here for a number of years. Parents have also been warned that children do not inherit immunity.
"It is a myth that children can inherit parents' immunity," said Dr Jack Lambert, a consultant specialising in infectious diseases in the Mater hospital in Dublin. "That is only the case for the first few months of life. Then, it is from antibodies in the placenta in the mother's womb crossing over into the baby but that immunity is washed out of the baby's system after the first few months of life. There is no such thing as natural immunity," Dr Lambert said.
Patients he has seen recently in the Mater include Africans who weren't aware that they had lost immunity to malaria after living here for a number of years. While they would have built up immunity from getting mosquito bites as they grew up in Africa, once they are no longer getting bitten regularly, the immunity starts to break down.
Dr Lambert said it was not possible to give a precise figure for how long immunity would last but after a period of five years a person would need to be vaccinated.
While malaria is one of the most common infectious diseases that holidaymakers, travellers and returning emigrants are putting themselves at risk of, other illnesses include Hepatitis A and B, yellow fever and travellers' diarrhoea.
The new 22-page booklet Healthy Travel, which is being launched today, advises all immigrants to consider the need for vaccination. It also gives advice on avoiding other travel-related hazards from water supplies to safe sex. It is produced by travel vaccine company Sanofi Pasteur MSD.
The number of malaria cases being reported in Ireland has been steadily increasing over recent years. Over the six-year period from 1999-2005 there were 462 discharges from hospitals with malaria as a primary or secondary diagnosis.
The number of cases notified to the Health Protection Surveillance Centre has been lower but a significant number of these occurred among people visiting family in their country of origin. Most of these did not believe they needed to take anti-malaria drugs.
The rise in holidays to long-haul destinations in Asia, Africa and Australia has also contributed to an increase in the numbers exposed to tropical illnesses. It has been found that up to 55 per cent of those travelling to at-risk countries are not taking the necessary precautions before travelling. Many people making these journeys are also unaware that it is necessary to get vaccinated some time before travelling, with just 35 per cent following the recommended schedule.