Chile says COVID - 19 vaccine is less effective in preventing symptomatic illness

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SANTIAGO, Aug 3 - Sinovac's COVID-19 vaccination was 58.5% effective in preventing symptomatic illness among millions of Chileans who received it between February and July, the Chilean health authorities said on Tuesday, while Pfizer's COVID 19 shot was 87.7% effective and AstraZeneca's was 68.7% effective.

The data came in the recent real world data published by Chilean authorities into the effectiveness of a raft of COVID - 19 vaccines among its population.

Chile began one of the fastest vaccination campaigns against COVID, in December having now fully vaccinated more than 60% of its population, predominantly with Sinovac's CoronaVac.

That vaccine was 86% effective in preventing hospitalization, 89.7% effective in preventing admission to intensive care units and 86% effective in preventing deaths within the population between February and July, health official Dr Rafael Araos said at a press conference on Tuesday.

In April the same study found that CoronaVac was 67% effective in preventing symptomatic illness, 85% effective in stopping hospitalizations and 80% effective in preventing deaths, suggesting its capacity to prevent the more serious impacts of the virus has diminished while its capacity to stop symptomatic illness was reduced.

Araos said a reduction in protection from vaccines was inevitable over time, especially with the arrival and growing prevalence of more virulent strains such as the Delta variant

If Delta becomes more prevalent and vaccine has a weaker response, we could observe a faster fall he said, adding his voice to calls for a third booster dose to be issued.

The government also issued data on the effectiveness of other vaccines, made by Pfizer BioNTech and AstraZeneca in Chile.

Pfizer's vaccine was 87.7% effective in preventing symptomatic COVID 19 in the same period, 98% effective in preventing intensive care admission and 100% effective in preventing death, Araos said.

AstraZeneca's was 68.7% effective in preventing symptomatic COVID-19 in the same period, 98% effective in preventing intensive care admissions and 100% effective in preventing death, Araos said.

Chile's study looked at vaccines' effectiveness among different cohorts of people who received either two doses of the specified vaccine, partial doses of the vaccine or no vaccine at all.

The CoronaVac part of the study examined a group of 8.6 million people, the Pfizer BioNTech part examined a group of 4.5 million people and the AstraZeneca part looked at a group of 2.3 million people