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A medical worker at a dedicated COVID-19 hospital in Seoul’s Gwangjin District monitors beds with screens on Tuesday. (Yonhap News)

An analysis of more than 2 million South Koreans shows that people over the age of 60 who have received a booster shot are 82.8% less likely to contract COVID-19 than those who have only received two vaccine doses.

That was one of the findings of an analysis of the preventive efficacy of COVID-19 booster shots in a survey of 2,350,207 people that South Korea’s Central Disease Control Headquarters released Wednesday. The analysis also showed that the risk of a case becoming serious or critical was 96.9% lower for those with the booster shot, while the likelihood of death was 99.1% lower.

This preliminary analysis covered 3,288,025 people aged 60 and above who had received their second dose of the AstraZeneca or Pfizer COVID-19 vaccine at least five months before and who had no record of infection through Oct. 25 of last year. The study observed these individuals for 54 days, between Oct. 25 and Dec. 18. Among this group, only 2,350,207 individuals were included in the analysis, which left out 937,818 people who had received a booster shot fewer than 14 days before the observation period ended.

Among the individuals in the analysis, 447,216 had not received a booster shot, and 1,902,991 had received a booster. During the 54 days of observation, there were 10,315 breakthrough infections among those who had not received their booster, and 880 among those who had. The breakthrough infections among those without a booster led to 543 serious or critical cases and 442 deaths, while the breakthrough infections among those with a booster led to four serious or critical cases and one death.

By Jang Hyeon-eun, staff reporter

Please direct questions or comments to [english@hani.co.kr]