(Bloomberg) -- Uruguay will give a Pfizer Inc. booster shot to people who have already received two doses of the less-effective Sinovac Biotech Ltd. vaccine, less than two weeks after the delta variant was detected in the South American country.

After 90 days of the second Sinovac jab, people can receive the mRNA shot from Pfizer. The government will offer a third shot to increase the population’s immunity to Covid-19 variants such as delta, said Graciela Perez, who leads the Health Ministry’s immunization unit. The Ministry will start scheduling those shots in August.

“This vaccine isn’t obligatory,” she told reporters in Montevideo. Uruguay has purchased enough Pfizer doses to cover the almost 1.5 million people eligible for a booster shot, she added.

Uruguay joins countries including the Dominican Republic, Thailand and the United Arab Emirates that plan to backstop Chinese made shots with mRNA vaccines in the hope of providing better protection against the rapidly spreading delta strain. A Covid-19 variant that originated in Brazil known as gamma has also been widespread.

Read More: Countries Using China, Astra Shots Increasingly Eye Boosters

Uruguay, which has about 3.5 million people, has fully vaccinated more than 61% of its population using shots from Sinovac, Pfizer or AstraZeneca, according to Health Ministry data. Coronavac, the shot produced by Sinovac, accounts for almost two-thirds of the more than 5.9 million shots Uruguay has received during the pandemic.

(Updates second and third paragraphs with comments from Health Ministry official)

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