Starting on Thursday, the federal government will begin delivering one million doses of the Moderna vaccine directly to pharmacies across the country. It’s part of a federal retail pharmacy program that will eventually expand supply to some 40,000 drug and grocery stores.

Those first million doses will reach around 6,500 retail pharmacies, covering about 10% of the nation’s pharmacies. They’ll be rolled out incrementally as the vaccine supply bottleneck slackens, with major chains like CVS Health, Walgreens, Walmart, Costco and Kroger likely to play a huge part in the effort.

The start of the program marks a shift in the country’s mass vaccination push, from administration primarily in traditional healthcare settings to smaller local sites that will be important in reaching broad swaths of the general public. But any number of challenges are likely to present themselves, particularly when it comes to the limited supply of vaccine doses and the question of whether there are enough for the vulnerable communities that need them most. At least so far, pharmacies and the government have shared few details around how they plan to mete out doses and track them to ensure that they’re reaching targeted populations.

At a press briefing last week, leaders of the National Association of Chain Drug Stores (NACDS) discussed the program’s initial rollout. During it, they preached patience.

“The supply of vaccines remains the rate-limiting factor in the vaccination effort,” said NACDS president and CEO Steven Anderson. “Pharmacies across America are prepared and have the experience to turn vaccination doses into vaccination appointments. That will continue to ramp up as the program is expanded and as vaccine supply becomes available.”

NACDS SVP of pharmacy care and patient advocacy Kathleen Jaeger added that pharmacies will be empowered to target populations based on their knowledge of the neighborhoods in which they operate. “This program is meant to be synergistic with what’s going on in the state, and to utilize the expertise and trust with community pharmacies and their neighborhoods,” she explained.

To date, the vaccination effort has been plagued by stark racial and ethnic disparities among vaccine recipients. In the first month of vaccinations, white people were being vaccinated at a much higher rate than Black and Latino people, according to data from the Centers for Disease Control and Prevention (CDC).

This is an area in which local pharmacies may be able to make a difference. “Community pharmacies are highly trained, highly trusted, they’re readily accessible, and are most often the first point of contact where patients tend to visit their pharmacist more times a year than their other providers,” said NACDS SVP of state strategic affairs and advocacy Christie Boutte. “Pharmacists can give patients information that is based on their medical history, which will educate patients in a manner to overcome the trust and hesitancy issues.”

Part of the vaccination effort will include the operation of pop-up sites in parking lots or schools in areas – whether urban or rural – that may be experiencing these disparities or vaccine hesitancy, although NACDS did not provide any details on where these pop-up sites would be located.

According to Jaeger, the program initially selected pharmacies based on their footprint per capita in areas that have the most vulnerable populations to COVID-19. However, the CDC has not yet listed the exact locations of all participating pharmacies. Similarly, when asked how the industry will track administration once doses arrive in stores – and specifically whether they’re successfully administered in the communities that need them most – Jaeger said there will be “performance metrics.”

“As we go forward, we’ll have a number of metrics that the pharmacies are going to be measured against. First will be waste, second will be throughput, third is social vulnerable index and fourth is data-recording,” she continued. “It’s incumbent upon our members to make sure they’re hitting the right populations as requested.”

It wasn’t stated when participating pharmacies would begin tracking these metrics, nor where they would publish their data.

Dr. Emmanuel Peprah, an assistant professor at New York University’s School of Global Public Health, said those metrics must be chosen carefully.

“So the question becomes where are [these pharmacy retail chains] shipping their supplies to, and who are they serving? What are their demographics they’re targeting?” Peprah said. “What are their criteria, what are they doing to reach those particular target populations? What are their plans, and have they published those plans in terms of their particular neighborhood?”

Peprah added that pharmacies will need to make sure that people in vulnerable communities have access to online registration for vaccine appointments.

The NACDS program is influenced by a similar one developed after the H1N1 pandemic, when the Obama administration requested that the CDC develop pandemic vaccine modeling, Jaeger noted.

“Stores receiving the allocation, a lot of those stores have done a lot of mapping,” she said. “Each of the stores know their location and populations. They know their community. They know the needs.”