PORTLAND, Ore. (AP) — Thousands of older Americans are spending hours online or enlisting their grandchildren’s help to sign up for a COVID-19 vaccine. They are the fortunate ones. An untold number of older people are getting left behind in the desperate dash for shots because they are too frail, overwhelmed, isolated or poor to navigate a system that favors healthier individuals with more resources. The urgency of reaching this vulnerable population is growing as more and more Americans in other age groups become eligible. Nonprofits, churches and health care outreach workers are scrambling to to reach older people who are falling through the cracks before the nation’s focus moves on and the competition for vaccines stiffens.