The number of babies who have died in the biggest outbreak of whooping cough for 20 years has increased to 10, health officials said.
Ten infants under the age of three months have died in England so far this year as a result of the infectious disease.
There were 1,322 confirmed cases in England and Wales in September alone, 300 more than the total figure for 2011 when there were 1,118 cases, the Health Protection Agency (HPA) said.
There were 6,121 confirmed cases between January and September this year, the HPA said.
In a move to combat the outbreak, health officials recently announced that all pregnant women are to be vaccinated against the infection.
Chief medical officer Professor Dame Sally Davies, the government's principal medical adviser, said that mothers-to-be will be offered the vaccination to protect their newborn babies.
Youngsters cannot receive the jab until they are two months old. Vaccinating their mothers before they are born will boost their immunity until they reach the age they can get the injection themselves, she said.
Women across the UK who are between 28 and 38 weeks pregnant are being offered the vaccination.
Increases in whooping cough are usually seen every three to four years. The last rise in the number of confirmed cases was recorded in 2008.
The largest number of cases have been in those over the age of 15 but there has also been a sharp rise in whooping cough in babies aged under three months.
Between January and September there were 350 cases reported in babies under three months, compared with just 115 cases in the whole of 2011.