Dataset Information

Serial Intervals and Incubation Periods of SARS-CoV-2 Omicron and Delta Variants, Singapore.

ABSTRACT: We compared serial intervals and incubation periods for SARS-CoV-2 Omicron BA.1 and BA.2 subvariants and Delta variants in Singapore. Median incubation period was 3 days for BA.1 versus 4 days for Delta. Serial interval was 2 days for BA.1 and 3 days for BA.2 but 4 days for Delta.

SUBMITTER: Zeng K

PROVIDER: S-EPMC10045676 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature

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Serial Intervals and Incubation Periods of SARS-CoV-2 Omicron and Delta Variants, Singapore.

Zeng Kangwei K Santhya Santhya S Soong Aijia A Malhotra Nitika N Pushparajah Dhanushanth D Thoon Koh Cheng KC Yeo Benny B Ho Zheng Jie Marc ZJM Cheng Mark Chen I MCI

Emerging infectious diseases 20230306 4

We compared serial intervals and incubation periods for SARS-CoV-2 Omicron BA.1 and BA.2 subvariants and Delta variants in Singapore. Median incubation period was 3 days for BA.1 versus 4 days for Delta. Serial interval was 2 days for BA.1 and 3 days for BA.2 but 4 days for Delta. ...[more]

PMID: 36878009

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Project description:Background The serial interval is the period of time between symptom onset in the primary case and symptom onset in the secondary case. Understanding the serial interval is important for determining transmission dynamics of infectious diseases like COVID-19, including the reproduction number and secondary attack rates, which could influence control measures. Early meta-analyses of COVID-19 reported serial intervals of 5.2 days (95% CI: 4.9–5.5) for the original wild-type variant and 5.2 days (95% CI: 4.87–5.47) for Alpha variant. The serial interval has been shown to decrease over the course of an epidemic for other respiratory diseases, which may be due to accumulating viral mutations and implementation of more effective nonpharmaceutical interventions. We therefore aggregated the literature to estimate serial intervals for Delta and Omicron variants. Methods This study followed Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A systematic literature search was conducted of PubMed, Scopus, Cochrane Library, ScienceDirect, and preprint server medRxiv for articles published from April 4, 2021, through May 23, 2023. Search terms were: (“serial interval” or “generation time”), (“Omicron” or “Delta”), and (“SARS-CoV-2” or “COVID-19”). Meta-analyses were done for Delta and Omicron variants using a restricted maximum-likelihood estimator model with a random effect for each study. Pooled average estimates and 95% confidence intervals (95% CI) are reported. Results There were 46,648 primary/secondary case pairs included for the meta-analysis of Delta and 18,324 for Omicron. Mean serial interval for included studies ranged from 2.3–5.8 days for Delta and 2.1–4.8 days for Omicron. The pooled mean serial interval for Delta was 3.9 days (95% CI: 3.4–4.3) (20 studies) and Omicron was 3.2 days (95% CI: 2.9–3.5) (20 studies). Mean estimated serial interval for BA.1 was 3.3 days (95% CI: 2.8–3.7) (11 studies), BA.2 was 2.9 days (95% CI: 2.7–3.1) (six studies), and BA.5 was 2.3 days (95% CI: 1.6–3.1) (three studies). Conclusions Serial interval estimates for Delta and Omicron were shorter than ancestral SARS-CoV-2 variants. More recent Omicron subvariants had even shorter serial intervals suggesting serial intervals may be shortening over time. This suggests more rapid transmission from one generation of cases to the next, consistent with the observed faster growth dynamic of these variants compared to their ancestors. Additional changes to the serial interval may occur as SARS-CoV-2 continues to circulate and evolve. Changes to population immunity (due to infection and/or vaccination) may further modify it. Supplementary Information The online version contains supplementary material available at 10.1186/s12879-023-08407-5.

Project description:In this study involving a cohort of employees of the National Airline company in Lebanon, we assessed humoral immunity levels and the effectiveness of two COVID-19 vaccines, Gam-COVID-Vac versus BNT162b2, after two doses and after a homologous and heterologous BNT162b2 booster, in addition to the impact of hybrid immunity. Vaccine effectiveness (VE) was retrospectively determined against laboratory-confirmed SARS-CoV-2 infection during the periods of Delta and Omicron variants' predominance, separately, and was calculated based on a case-control study design. The humoral immune response, measured by a SARS-CoV-2 anti-spike receptor-binding domain (RBD) IgG titer, was prospectively assessed after the aforementioned vaccination schemes at different time points. This study showed higher effectiveness of BNT162b2 after two doses (81%) compared to two doses of Gam-COVID-Vac (41.8%) against the Delta variant of SARS-CoV-2, which correlated with anti-spike antibody levels. Regarding the Omicron variant, protection against infection and antibody levels were severely compromised and the correlation between an anti-spike IgG titer and effectiveness was lost, unlike the situation during the Delta wave. Considering the booster vaccination schemes, a homologous BNT162b2 booster after a BNT162b2 primary vaccination induced a higher humoral immune response when compared to that induced by a heterologous BNT162b2 booster after a Gam-COVID-Vac primary vaccination. However, the VE of both booster regimens against the Omicron variant was almost equal (64% in the homologous regimen and 57% in heterologous regimen). Hybrid immunity evidenced a better humoral response and a greater and longer protection against Delta and Omicron infections compared to vaccination-induced immunity in COVID-19-naïve individuals. Finally, the findings show that VE waned with time during the same wave, highlighting the importance of reinforcing primary and booster COVID-19 vaccination mainly at the beginning of each wave during the surge of a new variant of concern.

Dataset Information

Serial Intervals and Incubation Periods of SARS-CoV-2 Omicron and Delta Variants, Singapore.

Publications

Serial Intervals and Incubation Periods of SARS-CoV-2 Omicron and Delta Variants, Singapore.

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