Young girls aged 12 to 15 are more likely to test positive for chlamydia than older teenagers and even women in their 20s, according to new research, prompting fears the girls are not practising safe sex.
More than one in 10 girls aged between 12 and 15 tested for chlamydia were found to carry the disease, according to an analysis of tests conducted in 15 laboratories across Australia between 2008 and 2010.
Researchers led by Burnet Institute epidemiologist Carol El-Hayek broke down the results by gender and across three age groups. They found girls aged 12-15 years had the highest percentage of positive tests (13 per cent), compared with females aged 16-19 years (12 per cent) and 20-24 years (8 per cent).
Among males, the highest percentage of positive tests was in those aged 16-19 years (15 per cent), followed by 20- to 24-year-olds (13 per cent) and 12- to 15-year-olds (9 per cent).
Ms El-Hayek said her study included about a dozen 12-year-old girls who had tested positive, but 14- and 15-year-olds were more commonly diagnosed.
Chlamydia is spread via unprotected vaginal, anal or oral sex and is often asymptomatic, but if left untreated can cause long-term complications including infertility.
Ms El-Hayek said her study showed fewer tests were performed on 12- to 15-year-old girls, possibly because they were tested only after presenting with symptoms or if identified as being at risk, whereas older women were screened more routinely.
"Clearly Australian adolescents as young as 12 are vulnerable to sexually transmitted infections but the younger they are, the less likely they are to be tested," she said.
The study, to be presented at the Australasian sexual health conference in Darwin on Thursday, comes as a new report by the Kirby Institute shows chlamydia remained the most frequently notified infection in Australia last year, with 82,707 cases diagnosed – up from 80,922 in 2011.
"Unfortunately this is just the tip of the iceberg," Kirby Institute program director David Wilson said. "It is likely that there are five times as many more Australians with chlamydia that is undiagnosed.
"We estimate that as many as one in 20 young Australians between the ages of 15 and 24 have chlamydia."