The latest expansion in South Korea’s COVID-19 vaccine portfolio, with more of the Pfizer product, is one less reason to put young people at potential clotting risk from AstraZeneca inoculations, some experts argue.

In an emergency news briefing Saturday, the Korean government announced it had sealed a deal to receive an additional 40 million doses of Pfizer’s COVID-19 vaccine. This brings the amount of Pfizer vaccine to 66 million doses.

The boost in the country’s Pfizer reservoir comes amid criticism the government has failed to secure enough alternatives to the AstraZeneca vaccine that is now being investigated over rare blood-clotting side effects.

To increase vaccine uptake, offering younger people a different vaccine that is free of such safety signals might be a viable option now that Korea is set to have more to come by, says virologist Dr. Paik Soon-young of Catholic University of Korea.

He said the reports of uncommon complications among younger recipients of the AstraZeneca vaccine, and the brief pause in its rollout for people under 60 years of age that followed, were probably accountable for recent reluctance to get the jab.

Only 61 percent of essential workers eligible for the AstraZeneca vaccine in April said they would get it, according to a government survey. The rate was lower at 52 percent for professions dominated by young women, such as flight attendants and preschool teachers, in whom the clotting events are more frequently observed.

By comparison, 83 percent of people aged 75 or older who are eligible for the Pfizer vaccine have said they intend to get vaccinated.

“Young people are already shunning the AstraZeneca vaccine, and understandably so,” said Paik. “The drama alone can cause public trust to dwindle.” Before the clotting issue became known, between 95 percent and 98 percent of people who were targeted in the initial phase of the AstraZeneca rollout had agreed to receive the vaccine.

He said that because weighing the benefits against the risks of the vaccination was complex for younger people, Korea could afford to exclude them for a couple of months until other supplies become more widely available in the second half.

“In the meantime, the vaccination program can focus on society’s more vulnerable members,” he said. Fewer than a million people aged 65 or above, who are at increased risk of severe illness from COVID-19, have received even a single shot.

Minister of Health and Welfare Kwon Deok-cheol said in Saturday’s briefing that about 100 million vaccine doses would be arriving in Korea between now and September.

“The quantity of vaccines Korea has locked in is more than enough to vaccinate the entire population twice,” the minister said. He said the country will have access to a total of 192 million doses over the year, with possibly more deals on the way. Minus some 20 million doses from AstraZeneca, the rest consists of Pfizer, Moderna, Novavax and Johnson & Johnson supplies.

The minister said he foresaw “no hurdles” in getting to the administration’s goal of a 70 percent first-dose vaccination rate by September, and then eventually to herd immunity before the end of November.

Despite the extra purchases, the Korea Disease Control and Prevention Agency’s Commissioner Jeong Eun-kyeong said in response to The Korea Herald’s question in the same briefing Saturday that allotting the country’s Pfizer shots to young people was “not being considered at the moment.”

“Our latest opinion is that the AstraZeneca vaccine is apt for use for people aged 30 and above,” she said. Still, she added, that could change if new evidence emerged.

Infectious disease professor Dr. Kim Woo-joo of Korea University said Korea’s decision to restrict the AstraZeneca vaccine only from people under 30 was not in line with the more cautious approach being taken in other countries. He pointed out that the small number of potentially vaccine-linked blood disorders reported here involved previously healthy people in their 20s to 50s.

“If we are getting the vaccines as outlined in the government timeline, I think it should allow us to be more strategic about how we assign our vaccine supplies to different groups,” he said.

Although the clotting conditions -- now termed vaccine-induced thrombotic thrombocytopenia or thrombosis with thrombocytopenia syndrome -- are treatable if detected early, they are much more severe than typical blood clots and can sometimes be fatal, he said.

“What worries me is that there appears to be no uniform guidelines on how these conditions might be treated,” he said.

Experts are unable to explain which component of the AstraZeneca vaccine is triggering these events, according to Dr. Jean-Louis Excler, who serves on the safety working group within COVAX, a global vaccine-sharing program.

“If there is a luxury of a choice, you could make a shift in how the vaccines are deployed as deemed necessary,” he said. France, for instance, was implementing similar age-based restrictions to the AstraZeneca vaccine, he said, adding that ultimately it was up to the regulators in individual countries to decide.

By Kim Arin (arin@heraldcorp.com)