The mixing of vaccines comes as the Mideast island nation struggles through its worst wave of the virus despite being one of the top countries in the world in per-capita inoculations.

The government's Be Aware mobile phone app allows those living in Bahrain to register for booster shots of either the Pfizer or the Sinopharm jabs. However, the government now recommends that people over 50, the obese and people with weakened immune systems receive the Pfizer shot regardless of whether they first received Sinopharm.

The Wall Street Journal in its Thursday edition quoted Waleed Khalifa al-Manea, Bahrain's undersecretary of health, as describing Sinopharm as providing a high degree of protection. But he acknowledged offering Pfizer to those with special needs, without explaining why the kingdom made that decision.

In response to questions from The Associated Press, Bahrain's government said “the people of Bahrain have a choice of vaccine when choosing their booster appointment six months after their original vaccinations”.

“All the data from the Ministry of Health has shown all the vaccines in use in Bahrain are providing similar high levels of protection against COVID-19,” the government said, adding that 90% of new cases in Bahrain were “people who had chosen to receive no vaccinations”.

Officials at Sinopharm did not immediately respond to a request for comment.

Last week, the company published data in a peer-reviewed article in the Journal of the American Medical Association, which concluded that the two vaccines are about 73% and 78% effective. However, the study involved mostly younger men and had little information about the vaccine's effectiveness against severe disease.

The two shots use different technologies. The Pfizer shots, a so-called “mRNA vaccine,” contain a piece of genetic code that trains the immune system to recognise the spiked protein on the surface of the virus. The Sinopharm vaccine is an “inactivated” shot made by growing the whole virus in a lab and then killing it.

The United Arab Emirates and Bahrain, both of which heavily relied on Sinopharm in their initial vaccination drives, announced in May that they'd offer a third shot of the Sinopharm vaccine amid concerns about an insufficient antibody response.

China's top disease control official acknowledged in April that the country's locally produced vaccines offer low protection against the virus, adding to growing questions over the shot's efficacy.

The World Health Organisation granted the Sinopharm shot emergency approval in May. A range of governments, including in Hungary, Pakistan, Serbia and the Seychelles, an island nation in the Indian Ocean, already administer Sinopharm.

In March, an official from a state-linked Emirati company distributing Sinopharm set off a storm of confusion when he acknowledged on Dubai's state-owned radio that “a very small number” of residents had already received booster shots of Sinopharm. As vaccine recipients became worried about their antibody levels, authorities there cautioned the public against mixing different coronavirus vaccines.

In April, the head of international cooperation at China National Biotec Group, which is a subsidiary of Sinopharm, described the UAE's use of booster shots as “not included in our clinical plan”.

In the UAE, home to Abu Dhabi and Dubai, some who earlier received Sinopharm have later gone back to be re-inoculated with the Pfizer vaccine as it became widely available across the federation of seven sheikhdoms.

The UAE and Bahrain rank among the world's top vaccinators on a per-capita basis. Yet Bahrain, home to some 1.6 million people, is in the throes of its worst wave yet of the virus, forcing the kingdom into a two-week lockdown.

Meanwhile on Thursday, sovereign wealth funds in Russia and Bahrain announced the island kingdom would begin producing the Sputnik V vaccine to supply demand across the Middle East and North Africa.

In Beirut, a senior World Bank official praised Lebanon's anti-pandemic program, despite what he said were problems in its early phase as the country remains embroiled in political infighting and lacks a fully functioning government.

“Despite the problems in the beginning, today we see the project is going in the right direction,” said Ferid Belhaj, the World Bank's vice president for the Middle East and North Africa.

The World Bank has been a major financier of Lebanon's coronavirus campaign. It has also financed the country's vaccination program, the first World Bank-financed operation to fund the procurement of COVID-19 vaccines, to provide for over 2 million individuals.

Lebanon has successfully managed to curb the second surge in coronavirus infections that had overwhelmed the health sector since the start of the year. Health authorities imposed a series of lockdowns while a vaccination campaign kicked off in February.

So far about 10% of Lebanon's 6 million have been inoculated. Efforts are underway to ramp that up.