Health officials recently announced that all pregnant women will be vaccinated against whooping cough in an attempt to combat the infection and protect newborns.
Responding to last month's figures on the outbreak, Dr Gayatri Amirthalingam, consultant epidemiologist for immunisation at the HPA, said:
The October figures show a continuing rise in the overall number of whooping cough cases. While there has been a decline in the number of infant cases it's important to emphasise that it's too early to see any impact from the pregnancy vaccination programme. Working with the Department of Health, we are continuing to carefully monitor whooping cough activity to evaluate the success of the programme.