Southeast Asia is reducing its reliance on Chinese Covid-19 vaccines, with some countries pivoting towards rival shots amid concerns about vaccine efficacy as the delta variant rips through their populations.

Public doubts about the Sinovac and Sinopharm vaccines against the highly contagious mutation could deal a blow to China’s vaccine diplomacy efforts in its own regional backyard. Asia is being ravaged by a fresh wave of Covid-19 which is causing record daily highs in many countries.

Fears have centred in particular on infections and even deaths among inoculated frontline health workers, prompting both Indonesia and Thailand this month to change their vaccine policies and offer booster shots of Moderna and AstraZeneca to medics.

In Indonesia, currently a global virus epicentre, Covid-19 is taking a devastating toll on healthcare workers, with 114 doctors dying so far this month alone, according to the Indonesian Medical Association.£

Covid-19 cases per million people (Asia/vaccines graphic)

In early July, the Thai health ministry confirmed that 618 medical workers out of 677,348 who had received two doses of Sinovac, had also been infected.

Malaysia last week announced it too would consider booster shots with either Pfizer-BioNTech or the AstraZeneca vaccines for people who had received a double shot of Sinovac.

The government, which is facing public discontent over soaring cases despite a strict and protracted lockdown, said it would stop administering Sinovac beyond its current stocks of 12 million doses, although Khairy Jamaluddin, the immunisation minister, denied the decision was linked to efficacy fears.

The slower release of data on Chinese vaccines has fanned efficacy doubts, even though Sinopharm was given emergency approval by the World Health Organisation in May, and Sinovac in June. No significant safety concerns have been flagged on either.

According to the WHO, Sinopharm’s efficacy in preventing symptomatic infection was 78% in the UAE, Bahrain, Egypt and Jordan combined.

Vaccines per million (Asia/vaccines graphic)

On July 7, the New England Journal of Medicine published the results of a study conducted among 10.2 million people vaccinated with Sinovac in Chile.

It found the vaccine to be 65.9% effective for the prevention of Covid-19, 87.5% for the prevention of hospitalisation, 90.3% for the prevention of ICU admission, and 86.3% for the prevention of Covid-19–related death.

Professor Benjamin Cowling, an epidemiologist of Hong Kong University, warned against letting “perfect be the enemy of the good” when considering the use of Chinese shots, which are produced from inactivated virus, similar to flu vaccines.

“Just because they are not perfect, doesn’t mean they are not good,” he said.

“There is no question that these vaccines are saving lives… inactivated vaccines have lower effectiveness against infection than some of the other vaccines but they still have very high levels of effectiveness against severe disease or death.”

Mr Cowling argued that in a situation of vaccine shortage, such as the one facing Southeast Asia, a less efficient vaccine was still better than none at all.

Sinovac, the leading vaccine developer and manufacturer in China, has exported some 150 million doses to Southeast Asia, including Indonesia, Malaysia, Thailand and the Philippines, at a time when global vaccine supply chains have struggled to meet demand.

“It’s very unfortunate that there have been these cases of deaths in healthcare workers but, acknowledging that the vaccines are highly effective, that means that a much worse situation has been averted,” he said.

“What we don’t have is a clear picture in many of these locations of the scale of infections in the community,” said Mr Cowling, adding that it was “disappointing” at this stage in the pandemic to see that infection control in countries like Indonesia had not been stepped up to protect medical workers.

Vaccine supplies in Southeast Asia

But he argued that more public data was needed on Chinese vaccines to address specific concerns about efficacy against the Delta variant.

Preliminary studies have suggested that inactivated virus vaccines could offer less protection against variants than the original virus.

A study published this week by scientists from the University of Sri Jayewardenepura as well as Colombo Municipal Council in Sri Lanka, and the University of Oxford in the United Kingdom, suggested Sinopharm’s vaccine elicited weaker antibody responses against the Delta variant.

Both Sinopharm and Sinovac were contacted for comment.

This week, Sinovac spokesperson Liu Peicheng told Malaysia’s Bernama that although there was a “reduction in its neutralising effect,” the vaccine “remains effective against the Delta variant.”

Some Southeast Asian nations now find themselves in a tight spot between assuaging their public that they are not being shortchanged over the best vaccines and the risk of upsetting China – one of their major trade partners – which is using vaccine diplomacy to extend its regional influence.

In Thailand, public anxiety was fuelled by a leaked document from the health ministry that quoted an official saying the offer of a Pfizer booster shot to medical workers would be "an admission that Sinovac can’t give protection".

“For Southeast Asian governments, concerns about potentially upsetting Beijing take a backseat to the immediate political priority of managing worsening outbreaks across the region, and the latter includes ensuring frontline workers in particular are given all possible protection,” said Peter Mumford, a regional analyst with the Eurasia Group.

He said governments faced a “tricky balance” to demonstrate they were diversifying supplies to counter the Delta variant while “also not exaggerating the risks from the Chinese vaccine and thereby potentially exacerbating broader vaccine hesitancy and causing undue alarm.”

Drew Thompson, a senior research fellow at the Lee Kuan Yew School of Public Policy at Singapore’s National University, said China’s vaccine diplomacy fit into the general pattern of Beijing’s increasingly assertive approach to foreign policy.

“China’s threat to only permit people who have been vaccinated with Chinese vaccines to enter China is a coercive tool and one which creates more pressure” on countries like Singapore or Malaysia with large ethnically Chinese populations with family ties to the mainland, he said.

But he added that Singapore, which is on track to vaccinate two thirds of its citizens by early August without including Sinovac in its official programme, had become “adept at striking that balance and standing up for itself, pursuing its own interests and not offending China.”

The biggest challenge to Asian governments might be facing down criticisms from their own public.

“It is a difficult communication exercise to persuade people that ‘something is better than nothing,’ because that’s not a good marketing slogan,” said Professor Cowling.

“People don’t want to settle for what they think is second best, if they can wait a little bit longer and get something better. But the limitations in supply are really a big issue.”