By CBSLA Staff

LOS ANGELES (CBSLA) — A large number of people in Los Angeles County may be overdue for their second dose of the COVID-19 vaccine.

Nathan Sanders gets his second dose of the COVID-19 vaccine at the Dignity Health Sports Park in Carson on Thursday, March 18, 2021. When asked if he’ll do anything special now that he’s vaccinated Sanders said, “No big plans, this isn’t over and I’m not stupid. (Photo by Brittany Murray/MediaNews Group/Long Beach Press-Telegram via Getty Images)

As of last week, public health officials say more than 4.5 million people in Los Angeles County have received at least one vaccine dose, while nearly 2.6 million have received a second dose. In her Monday briefing, Los Angeles County Department of Public Health Dr. Barbara Ferrer said about 278,000 were overdue for their second dose.

Most of those overdue for their second dose are between 18 and 64 years old, and county officials say people may be concerned about the side effects, believe that one shot is enough, or they simply forgot about their appointments, which are generally scheduled after receiving the first dose.

Los Angeles County is currently offering appointment-free, walk-up vaccinations at all of its large vaccination sites through Thursday.