In a Facebook post, Vichaiyut Hospital’s Dr Manoon Leechawengwongs cited the case of a 27-year-old nurse who had received two Sinovac jabs and two Pfizer boosters.
She developed a sore throat and tested positive for Covid-19 on February 19. She had contracted the virus from a family member and improved after spending 10 days in quarantine.
“However, she tested positive again on March 23 with a sore throat, cough and runny nose,” Dr Manoon said, adding that the patient recovered again after 10 days.
He said receiving four jabs can reduce the risk of developing severe symptoms and death even though it cannot protect people from contracting the virus.
He added that the nurse had received her fourth jab in January and a month later she contracted the virus. He believes the patient was infected by the Omicron BA.1 subvariant the first time and the BA.2 subvariant the second time.
“Normally, people who have been infected by BA.1 will have developed immunity against other subvariants, but some people can still contract the Omicron BA.2 because they are only immune to BA.1,” he said.
He added that this can happen to one in 4,000 people.