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Chile shifts Covid vaccine drive to second doses amid concerns over first shot's protection

The shift comes after data showed scant protection from one dose of the Sinovac Biotech (SVA.O) vaccine.
Image: A homeless man shows an ID reading 'I got vaccinated' after receiving a dose of Sinovac's CoronaVac vaccine in Santiago
A homeless man shows an ID reading 'I got vaccinated' after receiving a dose of Sinovac's CoronaVac vaccine in Santiago, Chile, March 26, 2021.Ivan Alvarado / Reuters file

Chile is shifting its Covid-19 vaccination strategy toward issuing second doses, while slowing administration of new shots, due to concerns over supply shortages and data showing scant protection from one dose of the Sinovac Biotech (SVA.O) vaccine that formed the backbone of its campaign.

The Andean nation, which has had one of the world's leading Covid-19 vaccination programs, has put more than 13 million shots into arms, and by Monday had about 2 million doses left in its warehouses, according to official figures.

At present, clinics are doling out an average of 153,000 vaccinations per day — well below March levels — as Chile aims to reach 15 million people, about 80% of its target population, and generate some level of herd immunity by mid-year.

That involves getting 2.3 million more people vaccinated with second doses of either of the two vaccines currently being used in Chile - from China's Sinovac and Pfizer Inc (PFE.N) - and inoculating another 7.3 million people.

In recent days, however, according to Reuters witnesses, clinics around Santiago, the capital, ran low of both vaccines, turning people away or asking them to wait several hours until more arrived.

More than 280,000 doses of the Pfizer/BioNTech shot and the first batch of 800,000 AstraZeneca Plc (AZN.L) doses that Chile will receive from the COVAX vaccine program are due to arrive in the coming week, the government said.

Beyond that, Chile is working to firm up other supply deals to keep its vaccination program on track.

The country is due 700,000 remaining doses from the 14.2 million it ordered of Sinovac's CoronaVac vaccine, which helped drive a mass inoculation campaign launched in February that has become the envy of Latin America.

Chile is waiting on just shy of 8 million Pfizer/BioNTech doses from a supply deal for more than 10 million. The government said the bulk would be delivered before the end of September, but could not provide fixed delivery dates.

Health Minister Enrique Paris said a strict vaccination calendar according to age groups was drawn up weekly to ensure Chile did not use up its supply before more arrived.

"I think we have to remain calm about this," Paris told reporters at a briefing on Monday. "We have a load of agreements with many different companies and the vaccines will keep coming."

Chile, which was vaccinating up to 430,000 people a day in March, has reached more than 50% of the 15 million people it aims to vaccinate by July with a single shot, while 36% have received both doses.

However, the country was hit by a second coronavirus wave in March with the end of the southern hemisphere summer holidays and more contagious virus variants first discovered in the UK and Brazil circulating.

Santiago and swathes of the country are under strict lockdown, with around 7,000 confirmed new COVID-19 cases reported each day.

"Could be much worse"

Unlike nations that are extending the gap between first and second doses to get more people some protection, Paris said Chile is now prioritizing second doses over firsts. The country aims to administer 760,000 second shots this week because of data showing a single dose of the Sinovac shot provides little protection.

Chile published its own analysis of the limited efficacy of Sinovac's CoronaVac vaccine on its population last week. The shot was only 16% effective in preventing infection and 36% effective at keeping people out of the hospital after one dose.

"If we don't administer the second dose, the situation could be much worse," Paris said.

By comparison, the risk of infection fell by 80% two weeks or more after the first Pfizer/BioNTech shot, according to the U.S. Centers for Disease Control and Prevention.

In addition to the first AstraZeneca doses expected to arrive through COVAX, the health minister said Chile has signed a deal to buy 1.8 million doses of a single-shot vaccine from CanSino Biologics (6185.HK).

Rodrigo Yanez, the Chilean trade vice minister in charge of acquisition of Covid-19 vaccines, told Reuters on Friday that the nation's rapid inoculation campaign made it "an attractive springboard" for vaccine manufacturers to test their wares. He said he was confident he could keep the supply taps open.

Yanez said his team was pushing Sinovac to deliver another 4 million doses, and that the first of 4 million doses purchased directly from AstraZeneca should begin arriving in May.

He said Chile was also speaking to Sinopharm and India about acquiring a supply of its Covaxin vaccine, and was in "advanced" talks with the Russian Direct Investment Fund to buy 5 million doses of the Sputnik V vaccine for delivery this year or next.

"We were planning to have different vaccines phasing in and out," Yanez said, adding that Pfizer will be prevalent in the program. "We are confident and positive we can reach herd immunity by the middle of the year."

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