LIMA, Peru — Tour operator Marco Arellano’s business shuttling tourists to Machu Picchu and the Amazon jungle effectively ground to a halt during the coronavirus pandemic. Now, as this South American nation is caught in the throes of a brutal second wave, he and millions of other Peruvians are putting their faith in one country to turn the deadly tide.

Peru has joined developing nations from North Africa to the Andes in counting on China for help. For these customers, the vaccines developed in Chinese laboratories and now being distributed globally could hold the solution to a massive problem: how to inoculate their populations after bigger and richer nations have pushed them to the back of the line for the more reliable vaccines developed in the West.

For Beijing, which has invested heavily in a region seen by Washington as America’s backyard, its vaccine diplomacy could be a double win: a way to open new markets for its pharmaceutical products while building goodwill in Latin America, a region where it has long sought to expand its influence.

But the opacity of the Chinese operations and the lack of published clinical data on the vaccines are raising questions about effectiveness and safety — and about the ability of Chinese laboratories to deliver millions of doses in double-quick time. In some countries, complaints over delays are already building.

For countries such as Peru, however, the Chinese vaccine is offering a possible fast track toward reaching herd immunity, or about 70 percent the population.

Peru this month reached deals for significant supplies of Western vaccines after months of being largely shut out by wealthier countries. Yet even if all of those agreements pan out — a challenge, given the delays and complications being witnessed in advanced economies — this country of 33 million would still only be able to inoculate about half its population without Chinese vaccines.

“The Chinese vaccine is a solution for a country like Peru,” Arellano said. He’s counting on his government’s pledge that its Chinese deal will allow mass vaccinations in the coming months and begin to revive the economy. “It will restore confidence.”

As the pandemic spills into 2021, vaccine rollouts even in many wealthy countries are going slowly. But in many developing nations, they haven’t started at all.

Critics warn of a potentially devastating gap in vaccine access between richer and poorer countries. The World Bank has said small and medium-sized developing nations could end up six months to a year behind larger developing nations and advanced economies in reaching “widespread” vaccine coverage. That gap could allow the pandemic — and its painful economic effects — to rage on far longer in the countries than can least afford it.

The World Health Organization says a global effort to get vaccines to many of those countries, known as Covax, is now on track, and has struck enough deals to meet a goal of distributing 2 billion doses by year’s end.

Yet that goal still amounts to relatively modest coverage — about 20 percent of the population in most countries reliant on the program. And some international health officials concede privately that even that might not be reachable.

One big problem: Wealthier nations have locked up so many doses of Western vaccines — in some cases securing contracts for two or three times their populations — that they’ve effectively squeezed out countries with shallower pockets and less diplomatic might. The Economist Intelligence Unit says dozens of developing nations might have to wait until 2023 for widespread inoculations.

“We have countries that have purchased huge amounts of vaccine,” said Jarbas Barbosa, assistant director of the Pan American Health Organization. “We will need more international solidarity.”

The scarcity has left developing countries looking to China, and, to a lesser extent, Russia. China’s state-run Sinopharm and private Chinese lab Sinovac Biotech have begun global rollouts. Trial data from Brazil showed the Sinovac vaccine to be only slightly more than 50 percent effective — compared to, say, the 95 percent rate for the Pfizer-BioNTech vaccine. Nevertheless, it already has a queue of clients, including Indonesia, Brazil, Thailand and Turkey.

The Sinopharm vaccine, with a self-reported efficacy rate of 79 percent but none of the publicly released clinical data issued by several Western vaccines, is being purchased more widely, by nations including Egypt, Cambodia, Senegal and Peru.

“Covid can be a real game changer for China,” said Jennifer Huang Bouey, a China expert and epidemiologist at the RAND Corporation. “They have never seen such large international demand for their pharmaceutical products.”

Few countries are counting on China more than Peru, which as recently as September had the world’s highest coronavirus mortality rate. Lockdowns have slammed the economy, sparking a recession that drove unemployment to 16 percent and spiked the poverty rate by 10 percentage points to nearly a third of the population. President Francisco Sagasti has announced a 14-day lockdown for Lima and nine regional departments, closing down all but a handful of essential sectors for just over one-half the population.

“Don’t even mention [the pandemic running into] 2022,” said Julia Mamani, a 26-year-old peddling water at a Lima traffic light. She lost her full-time job at a phone supply store that shuttered amid last’s year’s lockdowns. “I want things back to normal.”

So does most everyone else in Peru. Initial talks with Western laboratories were largely unsuccessful, hampered by its limited resources, the companies’ demands and the political turmoil that led to three presidents in nine days in November.

Sagasti has announced an agreement for 250,000 Pfizer doses in March and 300,000 more in April, part of larger deal for 20 million doses in “the coming months.”

He said another 517,000 doses — from both Pfizer and the Swedish-British firm AstraZeneca —would arrive via Covax by March, part of a pledge that includes 1.18 million more to come at some later date. Peru also has a private deal with AstraZeneca for 14 million doses due in September at the earliest.

Assuming all those doses arrive on time, they would cover a little more than half the population. Many would land after wealthier nations — including some of Peru’s better-off neighbors — are already well into their inoculation programs.

Enter China, a country that has displaced the United States as Peru’s top trading partner, and is now deeply involved in Peruvian mining, electricity distribution and shipping, including plans to build a gleaming new port near the capital.

Sinopharm started vaccine trials in Peru in September, using 11,800 volunteers. Last month, Sagasti announced a deal to buy 38 million doses of the two-shot vaccine, with the first million expected to arrive in the coming days. He suggested the vaccine, which does not require the specialized cold storage of others, would be delivered rapidly in the coming months, allowing the government to meet its target to vaccinate almost half the population before the start of the Southern Hemisphere winter in June.

Perhaps anticipating dissent, the president made a point of noting that it’s “perfectly safe.”

But critics say Peru, shut out of Western vaccines, has essentially been forced to buy a less trustworthy product.

“The fact that Peru and several other poorer countries are willing to enter these deals [with China] without full public transparency as to the vaccine’s effectiveness illustrates the mounting challenges they face in accessing the high-cost [Western] vaccines,” said Nicholas Lusiani, senior adviser at the anti-poverty group Oxfam America.

Without China’s vaccine, it could take Peru into distant 2022 before it reached herd immunity, prolonging both the pandemic and its economic pain. But doubts remain about China’s ability to deliver as fast as the Peruvian government hopes, and even Peruvian officials say they’re still working out a shipment timeline.

The Chinese Foreign Ministry has acknowledged the challenge.

“While striving to meet our huge domestic demand, we've been trying our best to advance vaccine cooperation with other countries through various means, especially with developing countries, to offer them much-needed support and help,” spokeswoman Hua Chunying told reporters in Beijing.

Sinopharm says it will make 1 billion doses this year for domestic and foreign use. Analysts estimate the firm’s current production capacity at 300 million doses, meaning it must build new factories or expand existing facilities to meet that target.

China National Pharmaceutical Group Corp. — Sinopharm — did not respond to a request for comment. Chinese media reports have not mentioned a delivery date for Peru’s 38 million doses, and state media have mentioned only the initial 1 million doses that have arrived.

“There are agreements, but we have to see when doses arrive and how they arrive,” said Angela Uyen, a Peruvian physician with Doctors Without Borders. “Will they come at once or in stages? Are we sure about the production capacity? These are questions that have not been answered.”

Peru faces a distribution challenge across a geography that ranges from soaring Andean peaks and remote villages along Amazon jungle rivers. The plans will be complicated by political instability and mounting allegations of corruption, which have further eroded trust in politicians, institutions and even vaccines.

Polls indicate any vaccine could be a hard sell here, particularly as conspiracy theories circulate — including false claims that the Sinopharm vaccine causes DNA mutations. According to Ipsos Peru, the percentage of Peruvians saying they would be vaccinated has fallen from 75 percent in August to 56 percent this month.

The rollout has now been marred by a scandal that media here have dubbed “vaccine-gate.” The country’s health minister and foreign affairs minister have stepped down after receiving Sinopharm’s vaccine in December and January while it was still in the experimental stage. The scandal began when former president Martín Vizcarra, who was impeached in November, admitted that he and his wife had been vaccinated in October.

Peruvian congressman and vaccine critic Posemoscrowte Chagua, a medical doctor, has objected to the Sinopharm deal.

“The Chinese vaccine should not be applied because it has not gone through rigorous clinical trials,” he said. “They have not finished Phase 3 of the trials and they want to start vaccinating people. This is unacceptable.”

The Peruvian Medical Federation, however, is on board. Infectious-disease specialist Ciro Maguiña, No. 2 at the federation, said he thinks the Sinopharm vaccine is safe.

“Sinopharm tests are above 75 percent, and a vaccine above 75 percent is successful,” he said.

Faiola reported from Miami. Dou reported from Seoul.