MERCEDES — Before doors opened to Hidalgo County’s first community COVID-19 vaccine clinic at 8 a.m., they announced they had reached their limit on social media.

After being vaccinated, people wait 15 minutes as recommended by the CDC to check for adverse reactions in the observation area Tuesday at the COVID-19 vaccination clinic on the Rio Grande Valley Livestock Show grounds in Mercedes.(Denise Cathey/The Brownsville Herald)

“This is one of many clinics to come,” Eddie Olivarez, Hidalgo County chief administrative officer for the Department of Health and Human Services, said.

Olivarez was one of several public officials who showed up for a news conference held at the Rio Grande Valley Livestock Show Grounds in Mercedes on Tuesday morning.

The vaccination clinic allowed healthcare workers, people over the age of 65, and people 18 years or older with certain medical conditions.

Residents showed up early to receive one of the 800 doses of the Moderna COVID-19 vaccine.

The first man in line, Rolando Zarate, said he started lining up since 2:30 a.m. Monday to assure he got a place in line.

County staff took temperature readings and asked vaccine candidates questions to determine eligibility.

Those who were not symptomatic for COVID-19 were allowed to proceed into the three-stage vaccination process.

A worker from the Hidalgo County Health and Human Services prepares to sanitize vacated chairs in the registration area Tuesday at the COVID-19 vaccination clinic on the Rio Grande Valley Livestock Show grounds in Mercedes.(Denise Cathey/The Brownsville Herald)

Large rooms with socially-distanced chairs and tables were set up to register groups of 100. Those who met the requirements were then allowed to receive the vaccine in the following room. The last room was dedicated to waiting. Medical providers stood by as those recently vaccinated were observed for 15 minutes to monitor for any adverse side effects.

The next vaccination event will be held on Thursday in La Joya at a destination which is expected to be announced Tuesday.

This story is developing.