SEOUL – Five South Koreans have died in the last two days after receiving the Covid-19 vaccine produced by AstraZeneca, sparking a presidential response and contributed to rising global concerns about the dose.

The presidential spokesperson said President Moon Jae-in may well take an AstraZeneca shot before heading for the G7 summit in the United Kingdom this summer.

According to local media reports, the five who died  two on Wednesday and three on Thursday  all had significant pre-existing medical conditions.

Korean health authorities are carrying out an investigation, and there is no direct scientific evidence yet showing that the deaths are directly linked to the vaccinations.

Still, the news is likely to be a blow to AstraZeneca, which has already suffered reputational blows in terms of its vaccine’s effectiveness compared with certain counterparts. It has also faced production bottlenecks which led to a political spat between the EU and UK, and has proven unpopular as a vaccine choice in Germany.

Yonhap newswire quoted health officials as saying one 52-year-old patient at a long-term care hospital died on Thursday morning, two days after being vaccinated. The patient had a cardio-cerebrovascular disease and in June suffered a brain hemorrhage.

The second patient, aged 58, died on Thursday at a different long-term care hospital, less than a day after receiving a shot. The patient’s pre-existing conditions included a myocardial infarction and diabetes.

The third death was of a woman in her 20s who passed away early Thursday after receiving the jab on Tuesday. She was also a patient at yet another long-term care hospital, though her pre-existing conditions have not yet been made public.

Thursday’s three deaths came on a day when national newspapers carried on their front pages reports of two deaths on Wednesday.A 50-something patient with multiple underlying diseases died at a long-term hospital on Wednesday after being vaccinated on Tuesday morning, health officials said according to local media reports. The patient’s pre-existing conditions included heart problems, diabetes and a stroke.

Wednesday’s second death, also a resident at a long-term care hospital, was a 63-year-old man with cerebrovascular disease who had been vaccinated last Saturday.

None of the patients was resident in the same facility. Health authorities have begun an investigation to discover if the deaths were related to the vaccinations.

As of late Wednesday, 87,428 South Koreans in high-risk categories had received inoculations in a program that only started last Friday. Of those, around 85,000 had taken the AstraZeneca jab with the remainder having been inoculated with the Pfizer vaccine.

Given that there is, as yet, no evidence linking the vaccinations with the deaths of patients suffering from serious underlying conditions, experts advised against jumping to conclusions.

“The number of vaccine-related deaths, accumulated worldwide, is about 40,” said Jung Sun-jae, a professor of epidemiology at the elite Yonsei University Medical School in Seoul. “But in this case we have not proved the causality between vaccination and death.”

Deaths soon after vaccinations can result from allergic reactions, but with no similar spates of deaths being reported from the AstraZeneca vaccine elsewhere, another expert advised that local and global issues need to be disentangled.

“We must understand the AstraZeneca vaccine in terms of the global experience, where death rates are not high,” said Ogan Gurel, a non-practicing US physician based in Seoul. “You have to look at local factors – patient selection, logistical issues and storage.”

He also noted that production could be a factor, given that the vaccine is manufactured under license in multiple locations. Both India and Thailand are licensed to produce the vaccine in Asia.

As a desperate world seeks an exit from the pandemic, vaccinations are on a surge worldwide. As of Wednesday, according to Bloomberg data, 271 million vaccine doses provided by multiple companies had been administered globally.

The AstroZeneca jab has not yet been approved for the country with the leading vaccination program, the United States, but is being massively administered elsewhere, notably in the UK, which has inoculated about 20 million people with either the AstraZeneca or Pfizer vaccines.

It is increasingly difficult to track how many vaccinations have been delivered by which manufacturer. Many countries are creating data based on the numbers of vaccinations, but few are breaking it down by specific vaccine.

Still, from the information available, it is clear that the AstraZeneca vaccine is being administered in massive numbers.

According to information collated by Our World in Data, some 468,879 doses of AstraZeneca have been administered in Germany, 404,392 in Italy, and 135,586 in Romania.

The Anglo-Swiss company’s vaccine, created in collaboration with Oxford University, is currently one of the world’s top three vaccines. Its price is significantly lower than that of the leading competitor, Pfizer, and it does not require the kind of deep refrigeration that the Pfizer product requires, making it more deployable and more economical.

Last October, fears – which have since subsided – were sparked after a Brazilian clinical trial volunteer died after receiving the AstraZeneca vaccine.

As of clinical trial data gathered in January, the Pfizer vaccine had a 95% efficiency rate, the Moderna vaccine had a 94.1% rate, while AstraZeneca lagged well behind with 70%.

The vaccine’s tribulations have continued since. It suffered a troubled rollout after supply-chain bottlenecks and related production problems resulted in a political tug-of-war and accusations of “vaccine nationalism” between the UK and the EU.

More recently, there has been resistance to what some consider a “second best” vaccine.

In Germany, which has taken delivery of 1.4 million doses of the AstraZeneca product, surveys show that around half of the population are reluctant to accept the vaccine.

According to reports earlier this week, this was not based purely on efficiency data but on the fact that Germany’s health authorities had refused to approve AstraZeneca for people over 65, citing a lack of data related to older individuals.

However, that changed on Wednesday when Chancellor Angela Merkel announced that the vaccine had been approved for over-65s.

It is not yet known if the deaths in South Korea will have a broader impact on the vaccine’s use locally or globally.

Gurel warned against knee-jerk reactions but made clear there must be a study. “This is not a reason for panic,” he said. “But it is a reason for careful investigation.”

Korean health authorities launched a probe after the first two deaths were reported – an investigation that will likely face new urgency after the three deaths reported on Thursday. But there has been no signal so far that Korea, which came very late to vaccinations and seeks herd immunity in November, will cease administering the AstraZeneca vaccine.

“Personally, I don’t think this will slow the vaccination movement,” said Jung of the Korean situation. “People will be concerned about adverse effects but in general I think the government will proceed.”

Still others fret that once the South Korean news spreads, it could lead to wider fears about not just AstraZeneca, but vaccines in general  fears prevalent in the “anti-vax” movement in parts of the world.

A German source, who has connections with his country’s health authorities, told Asia Times that the AstraZeneca situation “is endangering the entire world’s vaccinations.”