Tourists visit the Senado Square in south China's Macao, on May 3, 2021, the third day of China's five-day May Day holiday. (Xinhua/Cheong Kam Ka)

The Macao Special Administrative Region on Wednesday reported its first infection involving a coronavirus variant that was first detected in India, with the patient traveling abroad three days after getting the second dose of Sinopharm's COVID-19 vaccine.

A mainland expert said Thursday this was normal as it takes time to produce antibodies and achieve protection.

The Macao COVID-19 response and coordination center said on Wednesday that a man was found to have been infected with a coronavirus variant from India, B.1.617, on Monday, the first time the variant was found in Macao, reported now.com in Hong Kong.

The patient had two doses of the Sinopharm vaccine administered in Macao, on February 11 and March 11 respectively. On March 15, the patient left Macao for Hong Kong, and then went to Nepal at the end of March. From May 17 to 19, the patient returned to Macao from Nepal via Turkey, Paris and the island of Taiwan.

The patient was infected less than 14 days after the vaccination, and there may not have been enough time to develop sufficient immunity. But the patient was asymptomatic, suggesting that the vaccine still offered some protection, the center pointed out. 

"None of the COVID-19 vaccines so far offer a 100 percent protection rate, and it's normal that after vaccination, some people will still have the possibility of getting infected," Yang Zhanqiu, a deputy director of the pathogen biology department at Wuhan University, told the Global Times on Thursday. 

Yang also noted that it takes time for people who have received vaccines to produce antibodies.

"In the case of a live virus infection, it takes about seven days to start producing antibodies, while in the case of injecting inactivated vaccines, it will take longer, starting about two weeks after the first dose and taking about a month to achieve protection," Yang explained.

Yang said that the Sinopharm COVID-19 vaccine had helped to prevent a severe illness in the case reported by Macao. 

"As the patient was asymptomatic, it could be said the vaccination might have provided some protection against the development of severe disease in this case." 

The WHO on May 10 classified the coronavirus variant first identified in India in 2020 as a "variant of global concern" after some preliminary studies showed that it spreads more easily, according to media reports. 

A report released by the WHO on Wednesday showed that the variant B.1.617, first detected in India, has spread to at least 53 countries and regions.

Yang said that people should always take preventive measures such as wearing facial masks if they plan to go high-risk areas or go abroad, whether vaccinated or not, as there would still be some risk.

"The chance of getting infected will be much smaller for people to go those high-risk areas two weeks after getting the second shot of the vaccine," Yang noted.