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Volume 30, Number 7—July 2024
Dispatch

Vaccine Effectiveness against SARS-CoV-2 among Household Contacts during Omicron BA.2–Dominant Period, Japan

Tsuyoshi OgataComments to Author , Hideo Tanaka, Akemi Kon, Noriko Sakaibori, and Emiko Tanaka
Author affiliations: Itako Public Health Center of Ibaraki Prefectural Government, Itako, Japan (T. Ogata, A. Kon, N. Sakaibori, E. Tanaka); Public Health Center of Neyagawa City, Neyagawa, Osaka, Japan (H. Tanaka)

Main Article

Table 2

Household contact attack rates by vaccination status in a study of vaccine effectiveness against SARS-CoV-2 among household contacts during Omicron BA.2–dominant period, Japan*

Vaccination status of household contacts Vaccination status of index patients Total no. household contacts No. infected contacts Contact attack rate, % Risk ratio (95% CI)
No. vaccine doses
0–1 0–1 256 136 53.1 Referent
2 105 45 42.9 0.81 (0.63–1.03)
3 38 17 44.7 0.84 (0.58–1.22)
2–3 143 62 43.4 0.82 (0.66–1.02)
2 0–1 111 55 49.5 Referent
2 108 39 36.1 0.73 (0.53–0.997)
3 27 8 29.6 0.60 (0.32–1.10)
2–3 135 47 34.8 0.70 (0.52–0.95)
3 0–1 148 47 31.8 Referent
2 88 28 31.8 1.00 (0.68–1.47)
3 71 20 28.2 0.90 (0.57–1.38)
2–3
 159
 48
 30.2
 0.95 (0.68–1.33)
Vaccination status†
No recent vaccination 0–1 365 190 52.1 Referent
2 213 81 38.0 0.73 (0.60–0.89)
3 59 22 37.3 0.71 (0.51–1.01)
2–3 272 103 37.9 0.73 (0.61–0.87)
Recent vaccination 0–1 150 48 32.0 Referent
2 88 31 35.2 1.10 (0.76–1.59)
3 77 23 29.9 0.93 (0.62–1.41)
2–3 165 54 32.7 1.02 (0.74–1.41)

*Risk rates are stratified by vaccination doses or recent vaccination for household contacts or index patients. †Recent vaccination indicates last vaccine dose <3 months before illness.

Main Article

Page created: May 10, 2024
Page updated: June 22, 2024
Page reviewed: June 22, 2024
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