A five-week-old baby was admitted to Peel Health Campus last week with whooping cough (pertussis).
The baby is fine now and has been released from hospital.
Peel Health Campus chief executive Margaret Sturdy recommends pregnant mothers have the whooping cough vaccination in the last three months of their pregnancy.
She advised sick people to stay away from infants.
Dr Sturdy said grandparents should also prepare for the birth of their grandchildren by having their booster.
Pertussis is hard to diagnose in adults but as a general rule people who are sick with a cough, running nose, fever or any combination of these should try to avoid being close to newborn babies in the first few of months of their lives.
This is the second reported case of whooping cough in Mandurah.
A child from Mandurah Catholic College was treated for the disease earlier this month.
On June 17, the Coastal Times reported that there was a shortage of the whooping cough vaccine in Mandurah.
A spokeswoman for vaccine supplier Sanofi confirmed a worldwide shortage of the vaccine.
The supply of Adacel (adult whopping cough vaccine) to Australians was increased by 100 per cent in 2014 compared with 2013, and this year supply is expected to increase by a further 10 per cent, the spokeswoman said.
In March, Health Minister Kim Hames announced that all pregnant women would be offered free whooping cough vaccines, after the death of four-week-old Riley Hughes from the disease.
The Health Department have not linked a shortage of the vaccine with the recent reported cases of whooping cough.
A spokeswoman said the disease circulates all the time and has periodic increased activity.
“WA had its last big pertussis epidemic in 2011 to 12 and pertussis activity is currently relatively steady and at the lower end of levels experienced over the last couple of years,” she said.
“Around 20 cases are notified in the greater metropolitan area every week at present, so a couple of cases in the Mandurah area in a month would not be at all surprising.”