South Korea on Wednesday suspended providing the AstraZeneca shot to people under 60 as Europe reviewed cases of blood-clotting in adults.

People under 30 will still be excluded from the vaccinations resuming on Monday because the benefits of the shot do not outweigh the risks for that age group, the Korea Disease Control and Prevention Agency (KDCA) said in a statement.

Three vaccinated people in South Korea are reported to have developed blood clots, with one case determined to be correlated to the vaccine, Choi Eun-hwa, chair of the Korea Advisory Committee on Immunisation Practices, told a briefing.

That case was a type of blood clot considered less serious than those being examined by European authorities, she said.

For most people, the risks of coronavirus are far worse than the rare possibility of side effects from the vaccines, Choi said.

But she said, "the benefits are not as great for those under 30 years old, so we will not recommend the AstraZeneca vaccine for them".

The AstraZeneca shot's benefit-to-risk ratio rises the older people get as the risk of serious harm due to vaccination falls and intensive care unit admissions prevented by vaccination rise sharply, according to the University of Cambridge's Winton Centre for Risk and Evidence Communication.

The drugmaker has said its studies have found no higher risk of clots because of its vaccine, millions of doses of which have been administered worldwide.

The World Health Organization has said the benefits outweigh the risks.

Global controversy over the efficacy and side-effects of some COVID-19 vaccines has caused some delays in South Korea's vaccination campaign, which kicked off in late February with the goal of reaching herd immunity by November.

Australian Associated Press