As Delta drives COVID surge, vaccines, strategies under scrutiny

Questions raised about level of efficacy of WHO-approved shots from China as several countries eye booster shots using Western brands.

In early July, Singapore announced that people who received the Sinovac shots have been excluded from its count of total vaccinations against coronavirus, saying that not enough data on its efficacy had been made available [File: Chen Lin/Reuters]

Malaysia’s health ministry has announced that it will stop using the COVID-19 vaccine produced by China’s Sinovac once its supplies end, while other Southeast Asian countries have said they are looking to mix and match the Chinese-made shots with those from western manufacturers amid a surge in cases driven by the highly-transmissible Delta variant.

Malaysian Health Minister Adham Baba announced on Thursday that about half its 16 million doses of Sinovac have already been distributed and the remainder will be used to cover second doses.

The country will then use the Pfizer-BioNTech mRNA-type vaccine, having already secured about 45 million doses of the shot.

Malaysia’s decision on Sinovac’s inactivated virus vaccine comes amid questions elsewhere over the shot’s efficacy against new and more contagious variants of the coronavirus. The country reported a record 13,215 cases and 110 deaths on Thursday despite a prolonged lockdown, and has been ramping up its vaccination programme in an effort to bring the outbreak under control.

Sinovac as well as another China-made vaccine, Sinopharm, have received emergency use authorisation by the World Health Organization (WHO). Sinopharm is also classified under the inactivated virus vaccine category.


Malaysia has also approved the AstraZeneca jab, and on Friday announced the Drug Control Authority had approved the use of Johnson & Johnson as well as Sinopharm.

In neighbouring Thailand the government this week said it would give the AstraZeneca shot to those who had already received their first dose of the Sinovac vaccine, in an attempt to increase protection.

Thailand is the first country to publicly announce a plan to mix and match vaccines produced in China and ones developed by Western manufacturers.

Governments around the world are being forced to consider new approaches as the Delta variant – thought to be more transmissible and to become infectious to others more quickly – surges through their populations. Some are reviewing vaccine choices, as well as shortening the length of time between doses to ensure protection reaches the maximum level as quickly as possible.

A mixed schedule of vaccines has previously been tested in countries like Canada. A University of Oxford study published on June 28 also said that more antibodies were produced where a shot of Pfizer’s vaccine was given after an initial dose of AstraZeneca.

The World Health Organization (WHO), however, warned on July 12 against the practice, calling it a “dangerous trend” since there was little data available about the health effect, while Europe’s drug regulator made on July 14 said there were no definitive recommendations on switching doses.

‘Booster shot’

In Indonesia, which is battling Southeast Asia’s most severe coronavirus outbreak, the government has said it is considering a booster shot for those who have already received two doses of Sinovac.

Indonesia, which was the location of late-stage trials for Sinovac, has relied heavily on the Chinese-made vaccine for its immunisation programme but cases have continued to surge in the country of 270 million people.

The Philippines, meanwhile, has now received some 13 million doses of Sinovac doses after one million doses were delivered on Wednesday, according to the Philippine News Agency. The country expects to get 1.5 million more Sinovac doses on Saturday; the government has a total order of 26 million for the year.

On Friday, the health department confirmed at least 11 locally transmitted Delta variants of COVID-19 with at least one death.

Health officials have stressed that all the COVID-19 vaccines are effective, saying “the best vaccine is the one that’s available”.

In an interview with a Manila-based news channel, Philippine Food and Drug Administration chief Eric Domingo said that “theoretically” there was nothing bad about mixing China’s Sinovac with other brands. But because the practice had not been fully studied the government could not give its approval.

He says the country’s scientists are still doing a study looking into the use of Sinovac as first dose and other brands as a second dose or as a booster shot.

Western-made vaccines are also facing challenges as new variants emerge.

Last week, Israel’s Ministry of Health said the Pfizer vaccine’s efficacy against symptomatic COVID-19 infection went down from 97 percent in May to 64 percent more recently – suggesting that a booster might be needed. Pfizer itself has been lobbying in the United States over booster shots.

Canadian researchers, meanwhile, said that two shots of Pfizer are 87 percent protective against symptomatic infection by the Delta variant.

“No vaccine is perfect and a high enough dose of virus can overcome vaccine-induced defenses enough to cause an infection, though vaccine-induced immunity will limit disease severity in most cases,” Angela Rasmussen, a virologist affiliated to Georgetown University’s Center for Global Health Science and Security, wrote on Twitter in a thread about the Delta variant. “All this suggests we can control delta with the interventions we already have at our disposal.”

‘Alternative strategies’

Singapore, which has largely managed to keep the virus in check but is now battling an outbreak that began in a karaoke lounge, has used the Pfizer and Moderna jabs for its national immunisation programme.

Sinovac has been available privately but the Health and Sciences Authority (HSA) had asked the company for more data in order to evaluate its wider use. The company provided the information earlier this month, according to the Straits Times newspaper, but it will take at least four weeks for the HSA to come to a decision.

Meanwhile, those who opted for the Sinovac shots have been excluded from the country’s official vaccine count.

“We don’t really have a medical or scientific basis or have the data now to establish how effective Sinovac is in terms of infection and severe illnesses on Delta,” Health Minister Ong Ye Kung told the media last week.

In Hong Kong, meanwhile, which has also effectively controlled the pandemic, the government has used shots from Pfizer and Sinovac. About a quarter of the city’s population are now fully vaccinated.

A study published on Friday by researchers at the University of Hong Kong found there could be a need for “alternative strategies” for those given Sinovac. The study in the Lancet Microbe journal found healthcare workers given Pfizer had 10 times more antibodies than those who received Sinovac.

“The difference in concentrations of neutralising antibodies identified in our study could translate into substantial differences in vaccine effectiveness.” the researchers said.

In an interview with the South China Morning Post, the report’s lead epidemiologist, Benjamin Cowling, stressed that even a moderate level of protection was better than none at all, and urged people to get vaccinated.

“Don’t the perfect be the enemy of the good,” he told the newspaper.

With the Delta variant becoming dominant, it is not only in Asia where governments are reviewing their vaccine strategies in order to protect populations and safeguard gains made through rapid inoculation schemes.

The United Arab Emirates, which initially used the Sinopharm shot, has announced that it has made the Pfizer vaccine available as a booster.

A health worker prepares a vial of Chinese Sinovac vaccine inside a movie theatre-turned-vaccination centre in Metro Manila in the Philippines [File: Ted Aljibe/AFP]

The government said a different vaccine could be provided as a booster shot but this was at the recipient’s discretion and health professionals did not make recommendations about any brands.

Bahrain had also announced in June that eligible candidates could receive a booster shot of the Pfizer or Sinopharm vaccine, regardless of which shot they had initially taken.

Bhutan’s Prime Minister Lotay Tshering also announced on June 24 that he was comfortable about mixing and matching COVID-19 vaccine doses to immunise a population of about 700,000 people in the tiny Himalayan nation. More than 63 percent of the country’s population have already received a first COVID-19 shot, including 93 percent of the eligible adult population.

Bhutan had received 550,000 doses of the AstraZeneca vaccine from India in January and March. This month, it received the first batch of 500,000 Moderna vaccines from the US. It has also received 350,000 AstraZeneca shots from Denmark, Croatia and Bulgaria as well as 50,000 doses of Sinopharm from China.

China itself is also running an early-stage trial on the mixed inoculation of one dose of the vaccine from CanSino Biologics (CanSinoBIO), followed by one dose of the shot provided by a unit of Chongqing Zhifei Biological Products.

Researchers are also reportedly doing trials using one dose of CanSinoBIO’s shot as a booster for those who have already received one or two doses of an inactivated vaccine.

Source: Al Jazeera and news agencies