HOUSTON (AP) — Texas was scheduled to get more than 520,000 doses of the COVID-19 vaccine this week, more than state officials said they had originally expected to receive.

Texas Department of State Health Services officials said the boost in doses is due to two factors: a 30% increase in the Moderna vaccine that’s being provided by the federal government and a one-time return of 126,750 doses of the Pfizer vaccine that Texas had been required to set aside for a federal program that is vaccinating residents and staff at long-term care facilities.

The health department said these returned doses will be given to counties where allocations have been significantly less than their share of the population, particularly in the suburban Dallas-Fort Worth and Houston areas.

The Houston Health Department has said that this week it will focus its vaccine allocation on people at the highest risk for severe illness and those in vulnerable communities.

“We know it is important to vaccinate the people who are the most vulnerable, and they should be among the first to get shots, especially when supply is scarce,” said Mayor Sylvester Turner.

The state has received nearly 2.9 million doses of the coronavirus vaccine, according to the COVID Tracking Project.

Texas providers have administered nearly 2.3 million doses of vaccine, according to the state health department. More than 1.8 million people have received at least one dose, and more than 448,000 have been fully vaccinated.