Results from a new study indicate that hybrid laboratory antibodies derived from chimpanzees and humans may provide a potentially safe and effective way to treat the serious complications that can occur following smallpox vaccination--and possibly may even protect against the deadly disease itself. The study, led by researchers with the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), appears online this week in the Proceedings of the National Academy of Sciences (PNAS).