birth control

That was the limit of her formal sex education. For millions of young Chinese people, it's more than they ever got.

As China marks World AIDS Day Thursday, the effects of that missing knowledge is more evident than ever, with growing numbers of HIV infections and staggeringly high abortion rates.

No protection

In 2015, there were 115,000 new HIV infections in China, according to China's National Center for STD/AIDS Prevention and Control. Of those, 17,000, or 14.7%, were in the 15-24 age group.

US researchers say the jab was almost 96% effective in tests on around 270 men who were using it, with four pregnancies among their partners.

However, a relatively high number developed side effects, including acne and mood disorders.

Researchers have been investigating potential for male hormonal contraceptives for around 20 years.

They have all been looking for an effective way of suppressing sperm production without causing unpleasant or unbearable side effects.