AstraZeneca’s COVID-19 vaccine became available to people in their 30s and 40s this week, even though the official cutoff age hasn’t changed. This is leaving many people unsure, including medical professionals who say no real evidence was provided to support the change of policy.

Officially, the vaccine is recommended only for those 50 and older, due to the higher risk of rare but serious blood clotting as a side effect in younger people.

The Korea Disease Control and Prevention Agency, which oversees the vaccine program, said Friday that the AstraZeneca vaccination policy was changed to give younger people an option.

The agency said the age advice for AstraZeneca’s vaccine would remain unchanged due to a rare blood clot syndrome called thrombosis with thrombocytopenia syndrome, or TTS. Last month, the agency raised the age of eligibility from 30 to 50 years after a man in his 30s died in June from the syndrome.

“In principle, people under 50 will be offered mRNA vaccines,” the agency said in a message to reporters on Monday, implying the Pfizer and Moderna vaccines might be preferred for those in the age group. “People 30 and above can decide to get AstraZeneca’s vaccine if they wish,” it said.

During a closed-door briefing Wednesday, Hong Jeong-ik, head of the agency’s vaccination management division, said the agency “is not actively promoting that people 30 and older get the AstraZeneca vaccine.”

“While mRNA vaccinations are stalling, rather than limiting AstraZeneca’s vaccine to certain populations, people can weigh the known risks and benefits and decide for themselves if it is for them,” he said. About 3,200 people in their 30s and 6,700 people in their 40s chose to get the AstraZeneca vaccine in the past two days, according to Hong.

“People can make an informed decision based on an understanding of the side effects, and contemplate whether it is a risk they are willing to take against the backdrop of the current surge in infections,” he said.

Not all health professionals say they feel comfortable providing vaccinations against agency advice.

The Korean Physicians’ Association said in a statement Monday that the abrupt shift in AstraZeneca vaccination policy was not accompanied by an explanation. “The recommended age was changed to 50 years and above only about a month ago. Now the agency is saying the vaccine can be given to people as young as 30 without clear evidence to support it,” it said.

General practitioner Dr. Jang Hyun-jae in Nowon, northern Seoul, said public health officials never informed him of the age change, which took effect almost immediately after it was announced. “Many health providers, including myself, found out about it through the news, leaving us unprepared for patient consultation,” he said.

The Korea Vaccine Society’s vice president, Dr. Chun Byung-chul, said the agency hadn’t disclosed the estimated risk of side effects associated with the vaccine or provided other evidence behind the decision.

“The agency hasn’t made it clear that the benefits of AstraZeneca’s vaccine outweigh the risks in people younger than 50,” he said. “They’re not messaging clearly that young people will have more benefits than harm from AstraZeneca’s vaccine, but rather, that it is up to them to make that call.”

So far, out of 541,087 people aged 30-39 who received at least one dose of AstraZeneca’s vaccine in Korea, two were confirmed to have later developed TTS. Both were men, and one died.

Since the vaccination campaign kicked off in February, Korea has inoculated 46 percent of its 51 million people with at least one dose of a vaccine as of Tuesday, while 20 percent have been fully vaccinated.

By Kim Arin (arin@heraldcorp.com)