Chile weighing issue of third booster dose of COVID-19 vaccine

By Fabian Cambero

SANTIAGO, June 22 (Reuters) - Chile is studying the possibility of issuing a third, booster dose of COVID-19 vaccines, its president said on Tuesday, as the country seeks to beat back the latest wave of infections amid questions about how effective the widely used Sinovac vaccine is against more transmissible virus variants.

President Sebastian Pinera said health experts were examining "many scientific studies" to determine if a third dose would be necessary as he launched the rollout of vaccines among teenagers in Chile.

"As a government we are attentive to today's problems but also must anticipate and prepare to face the problems of tomorrow," he added.

Chile has relied heavily on the COVID-19 shot developed by China's Sinovac to roll out one of the world's fastest vaccination campaigns, administering 16.8 million doses, along with 3.9 million doses of the Pfizer/BioNTech vaccine and smaller amounts of inoculations from Cansino Biologics and AstraZeneca.

So far, 78% of Chile's target population has received at least one dose, and 61% are fully vaccinated.

Chile was an important early real-world test for the effectiveness of Sinovac's shot. In a study published in April, the Chinese vaccine proved minimally effective at preventing illness after one dose. With a second jab, it was 67% effective in preventing symptomatic infection, 85% effective in preventing hospitalizations and 80% in preventing deaths.

Public health chief Paula Daza told Chile's TVN news station that investigators were now examining how long Sinovac protection lasted, and would report back next month.

"We think that data will show that people who were vaccinated in February and had their second dose in March will likely need a third dose by September," she said.

With Chile predominantly relying on Sinovac, health officials are also facing questions about its ability to withstand some of the more contagious variants.

Earlier this week, more than 350 health workers who had been vaccinated with Sinovac's vaccine in an area of Indonesia hard-hit by the Delta variant fell ill with COVID-19.

No cases of the Delta variant, first identified in India, have been detected in Chile so far, though they have been in neighboring Peru and Argentina. (Reporting by Fabian Cambero, Writing by Aislinn Laing; Editing by Bill Berkrot)