To the roughly 400 clinical trials that have tested some experimental treatment for Alzheimer's disease and come up short, we can now add three more. An experimental drug called idalopirdine failed to help people with mild to moderate Alzheimer's disease in a trio of trials that involved 2,525 patients in 34 countries. Not only did the drug fail to bring about any meaningful change in cognitive tests that are widely used in diagnosing and tracking the progress of the disease, it also failed to cause significant improvements in general measures of daily function among those taking it at any of three tested doses.

Gene therapy could treat Type 1 diabetes

The newly resurgent field of gene therapy, which recently produced treatments for blood cancers and blindness, has taken a step toward fighting a scourge that is on the rise worldwide: diabetes. In research reported in the journal Cell Stem Cell, scientists showed that a single infusion of a virus containing two hand-picked genes restored normal blood sugar levels in mice with Type 1 diabetes. Although the effects of the therapy faded after four months, prompting the mice to return to their diabetic state, the equivalent improvement in humans could last for several years, the researchers said.

Fewer teens having sex, survey shows

The number of high-school-aged teens who are having sex dropped markedly over a decade, a trend that includes substantial declines among younger students, blacks and Hispanics, according to a government report. The survey by the Centers for Disease Control and Prevention showed especially steep declines in the past two years. It adds to evidence about ongoing progress in reducing risky behavior by teenagers, who are becoming pregnant, smoking cigarettes, drinking alcohol and using marijuana at lower rates than younger people before them, according to public health surveys.

Typhoid vaccine is approved by WHO

A new, highly effective typhoid vaccine — the only one safe for infants — has been approved for global use by the World Health Organization. Typhoid fever, caused by Salmonella typhi bacteria in sewage and contaminated food, infects up to 20 million people a year and kills up to 160,000 of them, mostly young children. The disease once killed many Americans — Typhoid Mary was a famous carrier — but is now found mostly in Africa and Asia. The need for an effective, affordable vaccine has risen urgently as urban slums grow, hotter weather spreads the disease to new regions and the bacteria develop resistance to more antibiotics. Approval means the new vaccine, named Typbar TCV and made by Bharat Biotech of Hyderabad, India, can be purchased by donors, including United Nations agencies, for use in poor countries.

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