New Mexico, Rhode Island, Tennessee and Texas were reportedly picked due to their size, population diversity, immunization infrastructure and need to reach people in both rural and urban settings.
Reuters reports this does not mean those states will receive the vaccine earlier than anyone else.
One key factor to distributing the vaccine is the temperature at which it must be kept. Most vaccines can be kept at 36-46 degrees Fahrenheit. But Pfizer COVID-19 vaccine needs to be shipped and stored at minus-94 degrees Fahrenheit, according to Reuters. That also potentially creates problems for hospitals which may not have the cold storage space necessary for the doses they need.
“We are hopeful that results from this vaccine delivery pilot will serve as the model for other U.S. states and international governments, as they prepare to implement effective COVID-19 vaccine programs,” Pfizer said in a statement to Reuters.
Moderna said Monday its COVID-19 vaccine appears to be 94.5% effective, according to preliminary data from an ongoing study. The news puts both companies on track to seek permission within weeks for emergency use in the U.S.
U.S. health officials said a coronavirus vaccine would need to be at least 50% effective before they would consider approving it for use. There was concern that coronavirus vaccines might be only as effective as flu vaccines, which have ranged from 20% to 60% effective in recent years.
The broad, early effectiveness figures don't tell the whole story. Scientists also need to understand how well the vaccine protects people in different age groups and demographic categories.
For both vaccines, the interim results were based on people who had COVID-19 symptoms that prompted a virus test. That means we don’t know yet whether someone who’s vaccinated might still get infected -- even if they show no symptoms -- and spread the virus.
Also unknown is whether the shots will give lasting protection, or whether boosters will be required.