It is people holidaying in exotic places without being vaccinated who are causing a rise in dangerous diseases including typhoid, warn doctors.
And low air fares could be fuelling the problem, they claim.
In the circumstances, health experts are launching a campaign Valuing Vaccines to spread the message about the importance of immunisation.
Dr Jane Zuckerman, director of the Centre for Travel Medicine at the Royal Free Hospital in north London, who is backing the campaign, said: "The level of public ignorance exposed by these results is extremely worrying.
"We have seen vaccine-preventable diseases like typhoid on the increase because people travel abroad to endemic areas without being vaccinated and return sick to the UK."
Typhoid is caused by the bacterium Salmonella Typhi and is picked up through contaminated food or water. The disease lasts several weeks and it takes people a long time to recover. It can be life-threatening unless treated promptly with antibiotics.
Typhoid kills 600,000 people worldwide each year. In 2002, 147 typhoid cases were reported in England and Wales, with 101 of those acquired abroad. In 2006, this had leapt to 248 cases, of which 122 were acquired abroad.
A milder strain of the disease, called paratyphoid and which cannot be vaccinated against, increased by 78% over the last five years.
A survey of more than 1,000 reveals more than 1 in 3 people in the UK are not aware of the diseases which can be prevented by vaccination.
Nearly two-thirds did not know that typhoid could be prevented by vaccination, while two out of five incorrectly believed there was a vaccine for malaria.
The Health Protection Agency said it was strongly in favour of the uptake of all recommended vaccines.
A spokeswoman added: "Although typhoid has increased the figures are still quite low and tend to show some yearly fluctuation."
TV personality, Tony Robinson, whose aunt died of the vaccine-preventable disease diphtheria, is leading the Valuing Vaccines campaign.
Diphtheria is also a very contagious and potentially life-threatening infection that usually attacks the throat and nose. In more serious cases, it can attack the nerves and heart. Because of widespread immunization, diphtheria is considered very rare in Europe and the United States.
People get diphtheria by breathing in diphtheria bacteria after an infected person has coughed or sneezed. People also get diphtheria from close contact with discharges from an infected person's mouth, nose, throat, or skin.
Globally, 2 million deaths per year are prevented by vaccination and the World Health Organisation estimates that this figure could reach 4 to 5 million annually by 2015.