Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:
HIV Vaccine Study Halted
A large study of an experimental HIV vaccine has been halted because the shots aren't preventing infection, the U.S. National Institutes of Health said Thursday. HIV is the virus that causes AIDS.
The clinical trial included about 2,500 people, mostly gay men, in 19 cities. Half of the participants were given the vaccine developed by the NIH and half received placebo shots, the AP reported.
A safety review found that slightly more people who had received the vaccine later became infected with HIV. The reasons for this aren't clear.
While the vaccinations are being stopped, the NIH said it will continue to track the study participants' health, the AP reported.
Numerous attempts to develop an HIV/AIDS vaccine have failed.
One-Fourth of U.S. Teens Admit to Impaired Driving: Survey
A new survey finds that 23 percent of American teens say they have gotten behind the wheel while under the influence of alcohol, marijuana or prescription drugs used illegally.
It also found that 34 percent of those who drive under the influence of marijuana say it improves their driving, as do nearly 20 percent of those who drink and drive, USA Today reported.
The survey of 1,708 students in grades 11 and 12 was conducted by Students Against Destructive Decisions (SADD) and insurer Liberty Mutual.
The percentage of teens who believe they can drive safely after drinking or using marijuana "seems high. But unfortunately, it's not surprising because teens think they're invincible and they thing nothing will happen to them. Unfortunately, sometimes it takes a friend or someone in their school getting killed before the reality kind of hits them," Cathy Chase, of Advocates for Highway and Auto Safety, told USA Today.
H7N9 Flu One of 'Most Lethal' Viruses So Far: WHO
The virus causing the current bird flu outbreak in China is one of the "most lethal" flu viruses ever seen, according to World Health Organization officials.
Health experts are especially concerned that the H7N9 virus jumps from birds to people more easily than the H5N1 virus that appeared in 2003 and has since killed 360 people worldwide, Dr. Keiji Fukuda, WHO's top influenza expert, said at a media briefing in Beijing, the Associated Press reported.
Another cause for worry is that H7N9 infects birds without causing noticeable symptoms, which makes it difficult to track its spread.
"This is definitely one of the most lethal influenza viruses we have seen so far," said Fukuda, the AP reported.
The H7N9 virus has infected more than 100 people in China. Most of them have become seriously ill and more than 20 have died. On Wednesday, Taiwan reported its first confirmed case of H7N9 bird flu in a man who became sick after returning from a visit to China.