The U.S. Centers for Disease Control and Prevention (CDC) said that the nation has distributed more than 11 million doses of the Pfizer and Moderna COVID vaccine, and over 2 million of those had been given to people as of Monday morning.

The CDC’s COVID Data Tracker showed the updated numbers as of 9 a.m. Monday.

“The distribution total is based on the CDC’s Vaccine Tracking System, and the administered total is based on reports from state and local public health departments, as well as updates from five federal agencies: the Bureau of Prisons, Veterans Administration, Department of Defense, Department of State, and Indian Health Services,” according to Medscape Medical News.

After the health providers administered the vaccine, they report to public health agencies within 72 hours, and the public health agencies report to the CDC after that, so there could be some lag in the data. The CDC will be updated more numbers on Mondays, Wednesdays, and Fridays.

The agency said, “A large difference between the number of doses distributed and the number of doses administered is expected at this point in the COVID vaccination program due to several factors.”

There could be delays in the reporting of doses administered and in managing vaccines. Also, there could be delays in the pending launch of vaccination.

The CDC said, “Numbers reported on other websites may differ from what is posted on CDC’s website because CDC’s overall numbers are validated through a data submission process with each jurisdiction.”

Reuters reported that on Saturday, the CDC’s tally showed the distribution of 9.5 million doses and administration of 1.9 million doses.

Nationwide, public health officials and health workers have started expressing their concerns over delays in administering the vaccines.

Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases (NIAID), told CNN, “We certainly are not at the numbers that we wanted to be at the end of December.”

Operation Warp Speed authorities had planned to administered COVID vaccine doses to at least 20 million people by the end of the year. Dr. Fauci said he hopes that number will be achieved next month.

He said, “I believe that as we get into January, we are going to see an increase in the momentum.”

There have also been shipment delays, which affected the administration of doses in priority groups. The NYPD anticipated a rollout on Tuesday, but it has been delayed since the department has not received enough Moderna doses, according to the New York Daily News.

Paul DiGiacomo, President of the Detectives’ Endowment Association, wrote on Monday, “We’ve made numerous attempts to get updated information, and when we get further word on its availability, we will immediately keep our members appraised of the new date and the method of distribution.”

“Every detective squad has been crushed with [COVID-19],” he added. “Within the last couple of weeks, we’ve had at least two detectives hospitalized.”

President-elect Joe Biden is expected to receive a briefing from his COVID-19 advisory team. After that, he will provide a general update on the pandemic and describe his plan to vaccinate people quickly. Biden has pledged to administer at least 100 million vaccine doses in his first 100 days in office, according to Medscape Medical News.