By Saeed Shah in Islamabad and Jon Emont in Singapore/Wall Street Journal Courtesy Ceylon Today

Islamabad, January 9 (Wall Street Journal): Governments and religious leaders in Muslim-majority nations are talking to vaccine makers, investigating production processes and issuing guidance in an effort to make sure concerns about products prohibited by Islam don’t interfere with Covid-19 inoculations.

On Friday, the high clerical council in Indonesia, with the world’s largest Muslim population, said that China’s Sinovac vaccine is allowed by Islam, or halal. The decision came after council representatives visited Sinovac’s factory in China last year and conducted a halal audit.

Part of the challenge of rolling out vaccines world-wide will be persuading enough people to take them to reach herd immunity. In many countries, Muslim and non-Muslim, the efforts must overcome safety concerns, suspicions and conspiracy theories, as well as religious and ethical objections.

Gelatin taken from pigs and cells created using tissue from human fetuses, which are both common in vaccine production, are aren’t halal, Muslim scholars say.

Acceptance of vaccinations before the coronavirus pandemic varied widely among Muslim countries, with high trust in countries like Bangladesh and Uzbekistan, according to a study of opinion in 149 countries published in September 2020 in the Lancet medical journal. It found that of the 10 countries with the most marked drop in confidence in vaccines over the four years through 2019, seven were predominantly Muslim: Afghanistan, Azerbaijan, Bosnia and Herzegovina, Indonesia, Malaysia, Nigeria and Pakistan. The other three were Japan, Georgia and Serbia.

In Pakistan, one of only two nations left on earth where polio is still endemic, the authorities have struggled for years to persuade people to let their children have the polio vaccine, with Islamic-related objections prominent among other concerns. Not only do some people contend that the vaccine isn’t halal—despite rulings from senior clerics there saying it is allowed—but an influential conspiracy theory contends that the West is using the inoculation to sterilize Muslims.

Two years ago in Indonesia, the official Muslim clerical organization that decides whether substances are halal ruled that a measles vaccine containing pig gelatin was permitted to be used in Indonesia owing to a lack of halal alternatives. Still, concern over the ingredients contained in the vaccine prompted some parents in conservative parts of the country to reject it for their children.

Those objecting to vaccines for various reasons are generally a minority among Muslims, but governments and religious leaders from Jakarta to Dubai are debating how best to address halal concerns to make sure they don’t become a significant obstacle to inoculating the world’s 1.8 billion Muslims.

This is a serious issue,” said Muhammad Munir, a virologist at Lancaster University in the U.K., adding that none of the Covid-19 vaccines that have so far reached late-stage trials ought to be a problem for Muslims because of the ingredients and processes involved. There is a responsibility on the [Muslim clergy] to have enough knowledge to guide the public properly.”

A vaccine developed by Moderna Inc. and another by Pfizer Inc. and BioNTech SE may offer a solution. They are synthetic, with no human- or animal-sourced ingredients, said Mr. Munir. However, these vaccines are in short supply globally and need to be kept at extremely cold temperatures, which will make distribution difficult in poorer countries.

The decision from Indonesia’s high clerical council Friday means that the Sinovac vaccine is ready for use in Indonesia as soon as the country’s food and drug regulator authorizes it, which is expected in the coming weeks.

Zulkifli Mohamad al-Bakri, the religious affairs minister of Malaysia, where Muslims make up more than 60% of the population, said in late December that a special religious committee had determined that Muslims should follow government instructions and take the vaccines, and noted that Muslims there have been encouraged to get inoculated for other diseases in the past.

A religious body in the United Arab Emirates last month issued an Islamic ruling, known as a fatwa, allowing Muslims there to receive coronavirus vaccines, even if they contain non-halal ingredients. The U.A.E. has already inoculated thousands for Covid-19 with a vaccine developed by Chinese drugmaker Sinopharm and has begun distribution of the Pfizer-BioNTech vaccine.

Such rulings on vaccination programs do not make the inoculations halal, but the vaccine can be used if there is no alternative available,” said Amrahi Buang, president of the Malaysian Pharmacists Society.

To be considered halal, manufacturers have to declare ingredients and give clerics the information they need to assess whether they comply with Islamic principles. To be halal certified, another level, the entire production line would need to be inspected, Mr. Buang said.

Aasim Padela, a professor at the Medical College of Wisconsin and head of the Initiative on Islam and Medicine, said that China could prove more responsive to the Muslim market, as it has in the past with other vaccines.

Anxiety has also been high enough in countries where Muslims are a minority, including the U.S. and the U.K., that Islamic groups there have felt obliged to issue rulings in recent weeks about which vaccines are halal.

Some Christians in the U.S. and elsewhere have also raised objections to the use of the fetal cell lines in Covid-19 inoculations. In December, the Vatican said it was morally acceptable for Catholics to receive such vaccines.

Even if a vaccine contains prohibited substances, Muslim scholars can also rule that the ingredients have been so transformed in the production process that their impure nature has been removed, Islamic experts say.

Rozi Osman, an independent halal consultant based in Malaysia, said that Islamic scripture makes clear that saving lives is more important than rigidly following rules.

Some Muslims are hung up about the halal part, which is ingrained from a young age,” Ms. Osman said. But to protect life is compulsory for Muslims. Some would rather listen to controversial voices rather than the truth.”

—Raffaele Huang, Chester Tay and Feliz Solomon contributed to this article.