Chile will begin administering a booster shot to those already inoculated with Sinovac’s COVID-19 vaccine, President Sebastian Pinera said on Thursday, August 5, after studies showed the initial two doses lose some effectiveness after several months.

Chile launched one of the world’s fastest mass inoculation campaigns against COVID-19 in February and has now fully vaccinated more than 60% of its population, predominantly with Sinovac’s CoronaVac.

“We have decided to start a reinforcement of the vaccination of those who have already received both doses of the vaccine Sinovac,” Pinera said in a televised address.

The country will begin administering an additional dose of Oxford’s Astrazeneca vaccine on August 11, beginning with citizens over 55 who received their shots before March 31.

Chile joins the United States, Germany, France, and Israel in giving booster shots, despite a plea by the World Health Organization to hold off until more people around the world can get their first shot.

Health subsecretary Paula Daza said domestic and international studies suggested the boosters would help reinforce immunity, but that Chile had already donated vaccines to its neighbors and would continue to help as needed.

“We are always analyzing the recommendations, and obviously the possibility of cooperating with other Latin American countries,” she said.

The death toll in Chile from the pandemic stands at 35,806 and there have been about 1.6 million confirmed cases in total.

Data released by the Chilean government on Tuesday, August 3, suggested CoronaVac’s effectiveness at preventing symptomatic infection among its recipients fell from 67% when measured between February and April, to 58.5% when measured again at the start of July. – Rappler.com