The Central Epidemic Command Center (CECC) on Thursday, Dec. 30, 2021, announced that it will not follow U.S. Centers for Disease Control and Prevention (CDC) guidance on shortened quarantines because some imported Omicron cases have been found to be infectious up to 12 days after testing positive.
On Monday (Dec. 27), the U.S. CDC shortened the recommended period that asymptomatic people should undergo quarantine after testing positive from 10 days to five, as long as they wear a mask for another five. It also shortened the isolation period for vaccinated people who have been exposed to the virus to five days.
During a press conference on Dec. 30, 2021, Philip Lo (羅一鈞), deputy head of the CECC’s medical response division, announced that a total of 59 imported Omicron cases have been detected in Taiwan. Of these cases, 55 were breakthrough infections, three had received one dose of a vaccine, and one had not been vaccinated.
More than 80% of these cases were detected upon arrival in Taiwan, while the rest tested positive within six days after entering the country.
CECC head Chen Shih-chung (陳時中) said that at present, it appears the incubation period of the Omicron variant is relatively short. Therefore, he stressed that the first seven days after entry are a very important line of defense.
He warned that if a cluster infection appears in a quarantine center or epidemic prevention hotel and is not detected in time, it could quickly spread into the community. If community transmission occurred, it would be a daunting task to contain, and the risk to society would increase substantially, Chen said.
A study by the New England Journal of Medicine released on Dec. 23 found vaccine recipients infected with COVID “may clear the infection more quickly than unvaccinated persons.” When asked to comment on this study, Lo explained that the research had been carried out on subjects infected with the Alpha and Delta variants and that vaccine efficacy with the Omicron strain remains to be seen.
Regarding the U.S. CDC’s recommendation to shorten quarantines from 10 to five days, Lo said 23 imported Omicron cases have been tracked for more than five days. He pointed out that of these cases, 17 had a Ct level of 30 or higher, meeting the standard to be released from quarantine.
Lo added that these cases did not reach this Ct level until at least eight days after they had fallen ill or tested positive. He said the longest it has taken for an Omicron case to reach the standard for release is 12 days after diagnosis.
Lo stated that after discussions with a panel of experts from the Ministry of Health and Welfare’s Advisory Committee for Immunization Practices (ACIP), the conclusion was that if quarantine stays were shortened to five days, there may still be a risk of infection and impact on community safety. Therefore, the experts advised that Taiwan not follow the U.S. guidance but continue to maintain the current quarantine regulations.
He explained that the current standard for releasing a COVID case from isolation is either 10 days after the onset of symptoms or a positive test followed by two consecutive tests resulting in a Ct value equal to or greater than 30.