Household transmission of the SARS-CoV-2 omicron variant in New Zealand, 2022

Nayyereh Aminisani; Q. Sue Huang; Lauren Jelley; Timothy Wood; Tineke Jennings; Danielle Currin; Ruth Seeds; Maritza Marull; Amanda Kvalsvig; Michael G. Baker; Nhung Nghiem; Paul G. Thomas; Richard J. Webby

doi:10.1016/j.jvacx.2025.100638

Household transmission of the SARS-CoV-2 omicron variant in New Zealand, 2022

Nayyereh Aminisani^*, Q. Sue Huang, Lauren Jelley, Timothy Wood, Tineke Jennings, Danielle Currin, Ruth Seeds, Maritza Marull, Amanda Kvalsvig, Michael G. Baker, Nhung Nghiem, Paul G. Thomas, Richard J. Webby,

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Background: Studying the transmissibility of the SARS-CoV-2 and its driving factors is valuable due to the ongoing emergence of new variants. We examined the household transmission characteristics of the Omicron-dominant variant.

Methods: The study took place in Wellington, New Zealand, from 7-February to 2-October 2022. When an individual had a confirmed case of SARS-CoV-2, all household members were instructed to take a swab every 3rd day until two consecutive negative swabs were obtained from the last person with SARS-CoV-2. Participants were monitored daily for acute respiratory symptoms until no further symptoms.

Results: We enrolled 75 households with confirmed cases of SARS-CoV-2 (total enrolled individuals = 306). The median serial interval was 4 days, and the secondary attack rate (SAR) was 60.6 % (95 % confidence interval (CI) 54.1–66.7). The SAR was higher for older household contacts and lower for contacts of fully vaccinated index cases. The SAR was highest when both the index case and the contacts were unvaccinated or received only one vaccine dose (88 %).

Conclusions: In this household cohort, the SARS-CoV-2 Omicron variant showed a high SAR which was modifiable by vaccination; the vaccination status of the index case and household members significantly reduced this.

Original language	English
Article number	100638
Pages (from-to)	1-7
Number of pages	7
Journal	Vaccine: X
Volume	24
Early online date	6 Apr 2025
DOIs	https://doi.org/10.1016/j.jvacx.2025.100638
Publication status	Published - Jun 2025
Externally published	Yes

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title = "Household transmission of the SARS-CoV-2 omicron variant in New Zealand, 2022",

abstract = "Background: Studying the transmissibility of the SARS-CoV-2 and its driving factors is valuable due to the ongoing emergence of new variants. We examined the household transmission characteristics of the Omicron-dominant variant. Methods: The study took place in Wellington, New Zealand, from 7-February to 2-October 2022. When an individual had a confirmed case of SARS-CoV-2, all household members were instructed to take a swab every 3rd day until two consecutive negative swabs were obtained from the last person with SARS-CoV-2. Participants were monitored daily for acute respiratory symptoms until no further symptoms. Results: We enrolled 75 households with confirmed cases of SARS-CoV-2 (total enrolled individuals = 306). The median serial interval was 4 days, and the secondary attack rate (SAR) was 60.6 % (95 % confidence interval (CI) 54.1–66.7). The SAR was higher for older household contacts and lower for contacts of fully vaccinated index cases. The SAR was highest when both the index case and the contacts were unvaccinated or received only one vaccine dose (88 %). Conclusions: In this household cohort, the SARS-CoV-2 Omicron variant showed a high SAR which was modifiable by vaccination; the vaccination status of the index case and household members significantly reduced this.",

keywords = "Household transmission, SARS-CoV-2 omicron variant, Secondary attack rate, Serial interval",

author = "Nayyereh Aminisani and Huang, {Q. Sue} and Lauren Jelley and Timothy Wood and Tineke Jennings and Danielle Currin and Ruth Seeds and Maritza Marull and Amanda Kvalsvig and Baker, {Michael G.} and Nhung Nghiem and Thomas, {Paul G.} and Webby, {Richard J.}",

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year = "2025",

month = jun,

doi = "10.1016/j.jvacx.2025.100638",

language = "English",

volume = "24",

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journal = "Vaccine: X",

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AU - Aminisani, Nayyereh

AU - Huang, Q. Sue

AU - Jelley, Lauren

AU - Wood, Timothy

AU - Jennings, Tineke

AU - Currin, Danielle

AU - Seeds, Ruth

AU - Marull, Maritza

AU - Kvalsvig, Amanda

AU - Baker, Michael G.

AU - Nghiem, Nhung

AU - Thomas, Paul G.

AU - Webby, Richard J.

PY - 2025/6

Y1 - 2025/6

N2 - Background: Studying the transmissibility of the SARS-CoV-2 and its driving factors is valuable due to the ongoing emergence of new variants. We examined the household transmission characteristics of the Omicron-dominant variant. Methods: The study took place in Wellington, New Zealand, from 7-February to 2-October 2022. When an individual had a confirmed case of SARS-CoV-2, all household members were instructed to take a swab every 3rd day until two consecutive negative swabs were obtained from the last person with SARS-CoV-2. Participants were monitored daily for acute respiratory symptoms until no further symptoms. Results: We enrolled 75 households with confirmed cases of SARS-CoV-2 (total enrolled individuals = 306). The median serial interval was 4 days, and the secondary attack rate (SAR) was 60.6 % (95 % confidence interval (CI) 54.1–66.7). The SAR was higher for older household contacts and lower for contacts of fully vaccinated index cases. The SAR was highest when both the index case and the contacts were unvaccinated or received only one vaccine dose (88 %). Conclusions: In this household cohort, the SARS-CoV-2 Omicron variant showed a high SAR which was modifiable by vaccination; the vaccination status of the index case and household members significantly reduced this.

AB - Background: Studying the transmissibility of the SARS-CoV-2 and its driving factors is valuable due to the ongoing emergence of new variants. We examined the household transmission characteristics of the Omicron-dominant variant. Methods: The study took place in Wellington, New Zealand, from 7-February to 2-October 2022. When an individual had a confirmed case of SARS-CoV-2, all household members were instructed to take a swab every 3rd day until two consecutive negative swabs were obtained from the last person with SARS-CoV-2. Participants were monitored daily for acute respiratory symptoms until no further symptoms. Results: We enrolled 75 households with confirmed cases of SARS-CoV-2 (total enrolled individuals = 306). The median serial interval was 4 days, and the secondary attack rate (SAR) was 60.6 % (95 % confidence interval (CI) 54.1–66.7). The SAR was higher for older household contacts and lower for contacts of fully vaccinated index cases. The SAR was highest when both the index case and the contacts were unvaccinated or received only one vaccine dose (88 %). Conclusions: In this household cohort, the SARS-CoV-2 Omicron variant showed a high SAR which was modifiable by vaccination; the vaccination status of the index case and household members significantly reduced this.

KW - Household transmission

KW - SARS-CoV-2 omicron variant

KW - Secondary attack rate

KW - Serial interval

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M1 - 100638

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Household transmission of the SARS-CoV-2 omicron variant in New Zealand, 2022

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