Shorter Incubation Period among Unvaccinated Delta Variant Coronavirus Disease 2019 Patients in Japan

Tsuyoshi Ogata, Hideo Tanaka, Fujiko Irie, Atsushi Hirayama and Yuki Takahashi
Additional contact information
Tsuyoshi Ogata: Itako Public Health Center of Ibaraki Prefectural Government, Itako 311-2422, Japan
Hideo Tanaka: Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan
Fujiko Irie: Tsuchiura Public Health Center of Ibaraki Prefectural Government, Tsuchiura 300-0812, Japan
Atsushi Hirayama: Department of Public Health and Medical Affairs, Osaka Prefectural Government, Osaka 540-8507, Japan
Yuki Takahashi: Fujiidera Public Health Center of Osaka Prefectural Government, Fujiidera 583-0024, Japan

IJERPH, 2022, vol. 19, issue 3, 1-15

Abstract: Few studies have assessed incubation periods of the severe acute respiratory syndrome coronavirus 2 Delta variant. This study aimed to elucidate the transmission dynamics, especially the incubation period, for the Delta variant compared with non-Delta strains. We studied unvaccinated coronavirus disease 2019 patients with definite single exposure date from August 2020 to September 2021 in Japan. The incubation periods were calculated and compared by Mann–Whitney U test for Delta (with L452R mutation) and non-Delta cases. We estimated mean and percentiles of incubation period by fitting parametric distribution to data in the Bayesian statistical framework. We enrolled 214 patients (121 Delta and 103 non-Delta cases) with one specific date of exposure to the virus. The mean incubation period was 3.7 days and 4.9 days for Delta and non-Delta cases, respectively ( p -value = 0.000). When lognormal distributions were fitted, the estimated mean incubation periods were 3.7 (95% credible interval (CI) 3.4–4.0) and 5.0 (95% CI 4.5–5.6) days for Delta and non-Delta cases, respectively. The estimated 97.5th percentile of incubation period was 6.9 (95% CI 5.9–8.0) days and 10.4 (95% CI 8.6–12.7) days for Delta and non–Delta cases, respectively. Unvaccinated Delta variant cases had shorter incubation periods than non–Delta variant cases.

Keywords: COVID-19; delta variant; incubation period; transmission time relative to symptom onset; serial interval; unvaccinated; Japan; SARS-CoV-2 (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

Downloads: (external link)
https://www.mdpi.com/1660-4601/19/3/1127/pdf (application/pdf)
https://www.mdpi.com/1660-4601/19/3/1127/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jijerp:v:19:y:2022:i:3:p:1127-:d:729080

Access Statistics for this article

IJERPH is currently edited by Ms. Jenna Liu

More articles in IJERPH from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().