An outbreak of whooping cough has sparked such a rush on vaccinations that remaining stock will be limited to small children and pregnant women.

Nearly three times as many people contracted whooping cough this year than last year - with 11,000 notifications to NSW Health compared with 3000 in 2014.

According to posts in a secret Facebook group, some chiropractors have been flouting the new rules. Credit:Greg Newington

NSW Health director of communicable diseases Vicky Sheppeard​ said supplies of the vaccine had been low for most of the year.

"That's resulted partly from the outbreaks which have generated demand, and also NSW and all states and territories have purchased a lot of the vaccine for pregnant women, so that has impacted the domestic supply."