Prevalence of Asymptomatic SARS-CoV-2 Infection in Japan.
JAMA Netw Open
; 5(12): e2247704, 2022 12 01.
Article
in English
| MEDLINE | ID: covidwho-2172229
ABSTRACT
Importance Real-world evidence of SARS-CoV-2 transmission is needed to understand the prevalence of infection in the Japanese population. Objective:
To conduct sentinel screening of the Japanese population to determine the prevalence of SARS-CoV-2 infection in asymptomatic individuals, with complementary analysis for symptomatic patients as reported by active epidemiologic surveillance used by the government. Design, Setting, andParticipants:
This cross-sectional study of a sentinel screening program investigated approximately 1 million asymptomatic individuals with polymerase chain reaction (PCR) testing for SARS-CoV-2 infection between February 22 and December 8, 2021. Participants included children, students, employed adults, and older individuals, as well as volunteers to broadly reflect the general Japanese population in the 14 prefectures of Japan that declared a state of emergency. Saliva samples and a cycle threshold (Ct) value of approximately 40 as standard in Japan were used. Polymerase chain reaction testing for symptomatic patients was separately done by public health authorities, and the results were obtained from the Ministry of Health, Labour, and Welfare of Japan to complement data on asymptomatic infections from the present study. Main Outcomes andMeasures:
Temporal trends in positivity and prevalence (including surges of different variants) and demographic associations (eg, age, geographic location, and vaccination status) were assessed.Results:
The positive rate of SARS-CoV-2 infection in 1â¯082â¯976 asymptomatic individuals (52.08% males; mean [SD] age 39.4 [15.7] years) was 0.03% (95% CI, 0.02%-0.05%) during periods without surges and a maximum of 0.33% (95% CI, 0.25%-0.43%) during peak surges at the Japanese standard Ct value of approximately 40; however, the positive rate would have been 10-fold less at a Ct value of 25 as used elsewhere in the world (eg, UK). There was an increase in patients with a positive PCR test result with a Ct value of 25 or 30 preceding surges in infection and hotspots of asymptomatic infections. Conclusions and Relevance In this cross-sectional study of asymptomatic SARS-CoV-2 infection in the general population of Japan in 2021, as investigated by sentinel surveillance, a low rate of infection was seen in the Japanese population compared with reported levels elsewhere in the world. This finding provides real-world data on the state of infection in Japan.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
COVID-19
Type of study:
Diagnostic study
/
Observational study
/
Randomized controlled trials
Topics:
Vaccines
/
Variants
Limits:
Adult
/
Child
/
Female
/
Humans
/
Male
Country/Region as subject:
Asia
Language:
English
Journal:
JAMA Netw Open
Year:
2022
Document Type:
Article
Affiliation country:
Jamanetworkopen.2022.47704
Similar
MEDLINE
...
LILACS
LIS