WINDOW ROCK, Ariz. (AP) — All Navajo Nation executive branch employees will need to be fully vaccinated against the virus that causes COVID-19 by the end of September or be required to submit to regular testing, according to an executive order announced by President Jonathan Nez on Sunday.

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The new rules apply to full, part-time and temporary employees, including those working for tribal enterprises like utilities, shopping centers and casinos. Any worker who does not show proof of vaccination by Sept. 29 must be tested every two weeks or face discipline.

“The bottom line is that we do not want to have another large surge in new COVID-19 cases that would harm our health care system and lead to more lives lost,” Nez said in a statement.

More than 80% of the tribe’s workers are already fully vaccinated but Nez said getting the rest inoculated is needed to ensure the workforce on the reservation can serve tribal members.

The tribe that spans parts of New Mexico, Utah and Arizona reported just 30 news cases on Sunday and no new deaths. The Navajo Nation was hard hit by the virus and closed its reservation for months last year. The tribe has confirmed 32,252 COVID-19 cases and 1,397 deaths.

Vaccine appointments are widely available.