First Dose of Chinese Covid-19 Vaccine Offers Little Protection, Chile Learns
The country vaccinated at record clip with shots developed by China’s Sinovac, then cases and deaths rose. Health experts say Chile dropped precautions too soon.

Several days after receiving his first dose of a Chinese-made coronavirus vaccine, Rodrigo Jordán fell ill and tested positive for Covid-19. The 61-year-old was hospitalized near his home in the Chilean capital, Santiago, for nine days and needed supplemental oxygen to pull through.
Across Chile—which has mounted one of the world’s most rapid vaccination campaigns using the vaccine made by Chinese drugmaker Sinovac Biotech Ltd.—health authorities are scrambling to deal with a surge in new infections and deaths.
More than 7.6 million people, half of Chile’s adult population, have already received at least one vaccine dose, most made by the Chinese drugmaker, making the country a real-world testing ground for a vaccine that Beijing is supplying to countries across the developing world.
The problem, public-health officials say, was that people in general overestimated the effectiveness of the vaccine after only one of the two recommended doses and moved to ease up on pandemic-control restrictions too soon.
“With one dose, we know the protection is very weak,” said Claudia Cortés, an infectious disease expert at the Santa Maria Clinic in Santiago, where about 10% of the Covid-19 patients at her hospital have received one shot. “It was not clearly explained that you need two doses—that you need to wait.”
It is a cautionary tale for other countries—from Brazil to Colombia in Latin America; Turkey to Indonesia in other corners of the globe—that have started to roll out the Sinovac vaccine.
On Friday, Chilean authorities released the results of a study of 10.5 million people, showing the vaccine was 16% effective against infection after one dose and 67% effective after a second dose. The study also found it to be 80% effective in preventing death from Covid-19 two weeks after a second dose.
A vaccination center at a Santiago stadium last month. Chilean officials are weighing whether a third dose of China’s CoronaVac vaccine may be needed.
Photo: Matias Basualdo/Zuma Press
That is lower than the vaccine made by Pfizer Inc. and BioNTech SE, for example. Research published in February in the Lancet medical journal found that one dose of the Pfizer and BioNTech vaccine was 85% effective in preventing symptomatic disease 15 to 28 days after being given, according to a peer-reviewed observational study of about 9,000 people in Israel.
Research also found the vaccine’s efficacy to be 91.3% up to six months after getting the second dose, Pfizer and BioNTech said.
In response to a request for comment, Sinovac pointed to the results of Friday’s study.
The lower protection from Sinovac’s single shot means the benefits of the vaccination campaign could take longer but health officials think some level of herd immunity will be reached by June or July.
However, health professionals say the virus will probably be around indefinitely, given the potential for new variants, many of which are already prevalent in neighboring countries such as Brazil. They warn that further restriction and lockdowns could be required.
Despite the surge, Chilean officials defend the vaccine, saying it is effective after the full regimen of two doses and is already helping to protect the elderly, making this surge less deadly.
While severe cases and infections among older people have been dropping, countless Chileans let their guard down too soon, public-health experts say.
“As a country, we trusted that, because of the vaccine, we were sort of out of it. But of course we aren’t,” said Mr. Jordán, a businessman and prominent mountaineer who has scaled Mt. Everest and maintained precautions after his first vaccine dose.
Independent public-health experts say the Chilean government sent confusing messages as it celebrated the vaccine rollout, by far Latin America’s fastest, and eased social restrictions to help the economy.
Police officers in Santiago enforced a curfew this month, as Chile’s capital went into lockdown again amid a surge in Covid-19 cases.
Photo: Marcelo Hernandez/Getty Images
Millions of Chileans worn out by the pandemic saw that as a green light to travel within the country during the Southern Hemisphere’s summer holidays.
People flocked to bars, restaurants and crowded beaches, many not wearing masks. Theater resumed, with the virus sweeping through one play, infecting virtually all of the actors and killing two. Young people held house parties, even though such gatherings remained prohibited.
Jaime Mañalich, who was health minister at the start of the pandemic, said the full two-dose regimen must be completed. “The fundamental message is that the start of a vaccination campaign is a very good thing, but you can’t relax the health measures,” he said.
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Camila Moya, a 28-year-old doctor, found out just how little protection she had after receiving her first dose. Infected with Covid-19, she developed a cough that shot pains into her chest. She has recovered now, but still has trouble breathing.
“You can’t relax with this virus,” she said. “Everything is uncertain.”
After health authorities in China recently spoke about experimenting with different doses and possibly adding a third shot, health officials in Chile have begun weighing whether to provide Chileans with a third shot, said Rafael Araos, an adviser to Chile’s current health minister.
“It is always an option,” said Mr. Araos, though details on the deliberations haven’t been made public.
Chile began vaccinating in December, but didn’t ramp up the campaign until the start of February after receiving its first shipment of Sinovac’s CoronaVac vaccines, which account for about 90% of all the shots administered.
More than 5 million Chileans, including 85% of those who are over 70 years of age, have received two shots. Government data shows a recent decline in elderly patients in hospital intensive-care units, with fewer dying.
A nurse checked an intubated Covid-19 patient last week in a hospital ICU in Concepción, Chile.
Photo: guillermo salgado/Agence France-Presse/Getty Images
Dr. Rodrigo Cornejo, the head of the ICU at the University of Chile’s hospital, said that last year that more than a dozen close colleagues died of the virus. Since medical staff have been fully vaccinated, he hasn’t heard of any doctors dying from Covid-19, he said.
In his intensive-care unit, patients used to be mostly older. Today, just six of the people in the 58 beds are over 70. Those patients, he said, became ill after receiving one shot of the vaccine or before getting full protection after the second dose, which takes two weeks.
“The situation is dramatically different,” he said. “Today, the elderly are the exception in the intensive-care units.”
Dr. Cornejo recalled recently holding the hand of a 29-year-old patient before he was put on a mechanical ventilator and pledging he would do all he could.
“He cried, he told me he was really scared and asked what would happen,” said Dr. Cornejo. “He couldn’t understand that he was in this situation.”
As restrictions eased at the start of the year, 26-year-old Benjamin de la Barra got together for meals with friends he hadn’t seen in months, though he hadn’t been vaccinated.
They always complied with government rules stipulating how many people could get together, he said. In late January, he suddenly lost his sense of taste and couldn’t smell his morning coffee. He tested positive for Covid-19, along with his family.
“Everyone felt there was a light at the end of the tunnel, that we were coming out of this. You felt freer and no longer restricted by the virus,” he said from Santiago, now in lockdown. “It’s surprising to be back in this position now.”
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Corrections & Amplifications
Serbia is receiving China’s Sinopharm vaccine. An earlier version of this article incorrectly said Serbia is receiving the vaccine made by Sinovac. (Corrected on April 18)
Write to Ryan Dube at ryan.dube@dowjones.com
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Appeared in the April 19, 2021, print edition as 'Chile Gets Dose of Reality.'