Health experts are warning of a major outbreak of whooping cough: five infants have died so far this year, prompting doctors to consider a new round of vaccinations.

The Health Protection Agency said on Friday it was very concerned by figures which show 2,466 confirmed cases between January and June, six times the comparable figure for the previous big outbreak in 2008.

The government's vaccination committee is now considering recommending booster vaccinations for teenagers and pregnant women and has already recommended immunising healthcare workers who treat young children because infants are most at risk.

Mary Ramsay, the agency's head of immunisation, said: "We are working closely with the Department of Health's Joint Committee of Vaccination and Immunisation to consider the most effective ways to tackle the ongoing outbreak. The committee is reviewing a number of options, including the introduction of a booster dose in teenagers and offering whooping cough vaccination to pregnant women.

"In the meantime we are actively reviewing our cases to see what interventions could have the quickest impact on the spread."

On average, in the last 10 years in England and Wales, 800 cases of whooping cough were reported, with more than 300 babies being admitted to hospital and four babies dying each year.

"Whooping cough can spread easily to close contacts such as household members," said Ramsay. "Vaccination is the most effective way to protect people from this infection and uptake of the vaccine in the UK is very good. In addition to this, parents should ensure their children are up to date with their vaccinations so that they are protected at the earliest opportunity.

"Whooping cough can be a very serious illness, especially in the very young. In older people it can be unpleasant, but does not usually lead to serious complications. Anyone showing signs and symptoms, which include severe coughing fits accompanied by the characteristic "whoop" sound in young children, but as a prolonged cough in older children and adults, should visit their GP."

Infants are routinely vaccinated against whooping cough at two, three and four months, with a booster three years later. Before vaccination became routinely available in 1957 large epidemics occurred every three to five years in the UK. These epidemics affected up to 150,000 people and contributed to about 300 deaths annually.