The South Korean government has decided not to administer AstraZeneca's COVID-19 vaccine to seniors 65 and older for the time being.

Following the decision, vaccinations are set to first begin on residents and workers at convalescent hospitals and senior care facilities who are under age 65.

The government seeks to ensure trust in the process by securing more clinical data amid controversy over the AstraZeneca vaccine's efficacy among older people.

But this may cause setbacks in the plan to vaccinate high risk groups in first order and the goal to achieve herd immunity by November.

The Korea Disease Control and Prevention Agency(KDCA) on Monday announced vaccination plans for February and March, saying 272-thousand residents and employees at nursing homes and rehabilitation facilities will first receive the shots starting February 26.

The next round of vaccinations will kick off on March 8 for healthcare workers at high-risk medical facilities. Other front-line COVID-19 workers including paramedics and first responders will be inoculated from March 22.

Officials explained they will verify further clinical information at the end of March and decide whether to use the AstraZeneca vaccine on seniors.

Though it had earlier provided authorization of the vaccine for all adults, Seoul's Food and Drug Safety Ministry cautioned its use on those 65 and above.