Two Chinese vaccine makers have said that their Covid-19 vaccines are effective at preventing serious illness, paving the way for their deployment in China and the developing world over the next few months.

The news indicates that China is likely to have four vaccines approved for general use — two vaccines are already being mass produced, by Sinopharm and Sinovac Biotech. The addition of two more could significantly speed up China’s mass inoculation drive, which has been slow in part because the government is prioritizing the export of its vaccines.

All the vaccines have been shown to prevent severe illness. But they have been dogged by a lack of transparency around clinical data.

CanSinoBIO, which has teamed up with a military institute that belongs to the People’s Liberation Army, said on Wednesday that its one-shot vaccine had an efficacy rate of 65.28 percent at preventing all symptomatic cases. Separately, Sinopharm, which has a vaccine that is already in use in China, said the shot that it developed with its affiliate, the Wuhan Institute of Biological Products, had an efficacy rate of 72.51 percent against Covid-19.

Both companies said they had asked Chinese regulators for approval for public use. They gave few details on their analyses, such as how many people contracted Covid-19 during the trials, giving scientists little data to make independent assessments.

Several developing countries have already ordered the vaccines, which can be easily stored at refrigerated temperatures.

Like other Chinese vaccine makers, CanSino had to go abroad to start its Phase 3 clinical trials, testing its vaccine in five countries: Argentina, Chile, Mexico Pakistan and Russia. The company’s vaccine has already been approved for use by the military.

Unlike Sinopharm and Sinovac, CanSino’s chief executive, Yu Xuefeng, has indicated that the company could struggle to ramp up production to meet the needs of China’s 1.4 billion people. Mr. Yu has said previously that the company’s vaccine production capacity was 100 million doses per year, or 200 million doses at the most.

The CanSino vaccine is made with a virus, called Ad5, that is modified to carry genetic instructions into a human cell. The cell begins making a coronavirus protein and the immune system learns to attack it. Before the release of the efficacy data, scientists were doubtful that the Ad5 vector would work effectively because it is a cold virus that many people are likely to have been exposed to.

Sinopharm tested its Wuhan vaccine in seven countries, including Bahrain, Egypt and the United Arab Emirates. In December, the vaccine that it developed with the Beijing Institute of Biological Production was approved for use. Like the Beijing vaccine, the Wuhan shot was made using a tried-and-tested technology that relies on a weakened virus to stimulate the immune system.

Both Sinopharm vaccines were approved in July for emergency use and rolled out to thousands of health care workers and travelers even before the completion of Phase 3 trials. The company said it could produce a maximum of one billion doses this year.