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Topline
A single dose of either the AstraZeneca or Pfizer Covid-19 vaccine is more than 86% effective in preventing infections among people aged 60 and older, according to real-world data released by South Korean authorities on Wednesday—findings which will likely vindicate calls for expanded rollouts of vaccines that prioritize first doses to ensure a large portion of the population has some protection.
South Korean Olympic judo team player An Ba-ul receives the first dose of the Pfizer-BioNTech … [+]
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Key Facts
According to Reuters, data released by the Korea Disease Control and Prevention Agency (KDCA) showed the Pfizer vaccine was 89.7% effective in preventing Covid infection two weeks after the first dose was administered, while the AstraZeneca shot was 86.0% effective.
The KDCA’s findings were based on analysis of data from 3.5 million people in the country who are 60 or older— including 521,133 people who received their first dose—for two months from February 26.
A total of 1,237 Covid-19 cases were reported from the overall cohort, however, only 29 were from the vaccinated group.
A health ministry official also noted the possibility of side effects from the shots including blood clotting are “extremely low” and mostly curable.
Big Number
6.7%. That’s the total percentage of South Koreans who have received a single dose of a Covid-19 vaccine, while only 0.5% have been fully vaccinated, according to Bloomberg’s global vaccine rollout tracker. The country has set a target of immunizing 70% of its population by September, and reaching herd immunity by November.
Tangent
However, it is unclear if the high effectiveness of single doses seen in South Korea—which has largely managed to keep the pandemic in check—is an anomaly. In its large-scale trial data released in March, AstraZeneca found that two doses of its vaccines are 76% effective in preventing symptomatic Covid-19, which is significantly lower than the KDCA’s finding that one dose is 86.0% effective in preventing infections. Pfizer, on the other hand, has reported 95% efficacy from two doses, which expectedly is higher than KDCA’s 89.7% number from a single dose. The KDCA’s findings make no mention of the impact of the more infectious U.K., South African and Brazilian variants of the coronavirus on the vaccine’s efficacy, which could be a reason behind the discrepancy.
Key Background
The findings will likely vindicate countries like the United Kingdom, which has prioritized the rollout of first doses, ensuring that more than half of its population has received at least one dose. Despite their success in taming the pandemic so far, several Asian countries like South Korea, Taiwan and Japan have been sluggish in their vaccine rollouts. The new findings and relatively low incidence of cases in those countries may allow them to adopt a Britain-like strategy to speed up their rollout. South Korean authorities, however, didn’t make any such suggestion on Wednesday, and instead noted that people should get “full vaccinations according to the recommended schedule”, as it will offer even stronger protection.
Further Reading
S. Korea says AstraZeneca, Pfizer COVID-19 vaccines 87% effective after first shot (Reuters)
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