Meggan Ingram was fully vaccinated when she tested positive for COVID-19 early this month. The 37-year-old’s fever had spiked to 103 and her breath was coming in ragged bursts when an ambulance rushed her to an emergency room in Pasco, Washington, on Aug. 10. For three hours she was given oxygen and intravenous steroids, but she was ultimately sent home without being admitted.

Seven people in her house have now tested positive. Five were fully vaccinated and two of the children are too young to get a vaccine.

As the pandemic enters a critical new phase, public health authorities continue to lack data on crucial questions, just as they did when COVID-19 first tore through the United States in the spring of 2020. Today there remains no full understanding on how the aggressively contagious delta variant spreads among the nearly 200 million partially or fully vaccinated Americans like Ingram, or on how many are getting sick.

The nation is flying blind yet again, critics say, because on May 1 of this year — as the new variant found […]