Employees across the massive U.S. Health and Human Services Department received notices Tuesday that their jobs were being eliminated, part of a sweeping overhaul designed to vastly shrink the agencies responsible for protecting and promoting Americans’ health. The cuts include researchers, scientists, doctors, support staff and senior leaders, leaving the government without many of the key experts who have long guided U.S. decisions on medical research, drug approvals and other issues. HHS said layoffs are expected to save $1.8 billion annually — about 0.1% — from the department’s $1.7 trillion budget, most of which is spent on Medicare and Medicaid health insurance coverage for millions of Americans.