BANGKOK — Medical workers in Thailand who have received two doses of China’s Sinovac coronavirus vaccine will be given a booster shot of AstraZeneca vaccine, Thai health authorities announced Monday.

Thailand is fighting a sharp surge in COVID-19 cases, and a nighttime curfew and other heightened measures began in Bangkok and several other provinces on Monday. The surge has been accompanied by the spread of the more contagious delta variant of the virus. A Thai Red Cross scientist, Dr. Thiravat Hemachudha, says Sinovac is less effective at fighting that variant.

The decision to provide AstraZeneca booster shots was made after a nurse who received two doses of Sinovac in May died last week, and more than 600 others who received Sinovac tested positive for COVID-19. Other Thais who have received only one dose of Sinovac will be able to get AstraZeneca for their second dose, Health Minister Anutin Charnvirakul said.

Thailand reported 8,656 new cases and 80 deaths on Monday, bringing its total since the pandemic began last year to 345,027 confirmed cases and 2,791 deaths. More than 90% of the cases and 95% of the deaths have occurred since the third surge began in early April.