The report also showed that teens from low-income families were more likely to not use a condom.
Condom use among sexually active teens has declined significantly in Europe over the past decade, with rates of unprotected sex "worryingly high", the World Health Organization said Thursday.
"This is putting young people at significant risk of sexually transmitted infections (STIs) and unplanned pregnancies," WHO Europe said in a statement.
Data from a survey of more than 242,000 15-year-olds across 42 of the 53 countries that make up the WHO European region, which includes Central Asia, showed that the proportion of sexually active teenage boys who used a condom the last time they had sex fell from 70 percent in 2014 to 61 percent in 2022.
The figure for girls who said a condom had been used the last time they had sex fell from 63 to 57 percent.
Almost a third of adolescents said they used neither a condom nor a contraceptive pill the last time they had intercourse, largely unchanged from 2018.
Use of contraceptive pills also remained relatively stable between 2014 and 2022, with 26 percent of 15-year-olds reporting that they or their partner had used it the last time they had sex.
The report also showed that teens from low-income families were more likely to not use a condom or a pill, with 33 percent reporting using neither during their last intercourse, compared to 25 percent from more affluent families.
"Age-appropriate comprehensive sexuality education remains neglected in many countries, and where it is available, it has increasingly come under attack in recent years on the false premise that it encourages sexual behaviour," WHO Europe director Hans Kluge said in a statement.
"The truth is that equipping young persons with the right knowledge at the right time leads to optimal health outcomes linked to responsible behaviour and choices," he said.
The WHO said that in addition to higher rates of STIs and unplanned pregnancies, inadequate sexuality education also leads to increased healthcare costs and disrupted education and career paths for young people.
"We are reaping the bitter fruit of these reactionary efforts, with worse to come unless governments, health authorities, the education sector and other essential stakeholders truly recognise the root causes of the current situation and take steps to rectify it," it said.
The agency urged policymakers, educators and healthcare providers to invest in comprehensive sexuality education, improve access to sexual health services, promote dialogue and better train educators.
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