Index cases first identified by nasal-swab rapid COVID-19 tests had more transmission to household contacts than cases identified by other test types

Abstract

At-home rapid COVID-19 tests in the U.S. utilize nasal-swab specimens and require high viral loads to reliably give positive results. Longitudinal studies from the onset of infection have found infectious virus can present in oral specimens days before nasal. Detection and initiation of infection-control practices may therefore be delayed when nasal-swab rapid tests are used, resulting in greater transmission to contacts. We assessed whether index cases first identified by rapid nasal-swab COVID-19 tests had more transmission to household contacts than index cases who used other test types (tests with higher analytical sensitivity and/or non-nasal specimen types). In this observational cohort study, 370 individuals from 85 households with a recent COVID-19 case were screened at least daily by RT-qPCR on one or more self-collected upper-respiratory specimen types. A two-level random intercept model was used to assess the association between the infection outcome of household contacts and each covariable (household size, race/ethnicity, age, vaccination status, viral variant, infection-control practices, and whether a rapid nasal-swab test was used to initially identify the household index case). Transmission was quantified by adjusted secondary attack rates (aSAR) and adjusted odds ratios (aOR). An aSAR of 53.6% (95% CI 38.8–68.3%) was observed among households where the index case first tested positive by a rapid nasal-swab COVID-19 test, which was significantly higher than the aSAR for households where the index case utilized another test type (27.2% 95% CI 19.5–35.0%, P = 0.003 pairwise comparisons of predictive margins). We observed an aOR of 4.90 (95% CI 1.65–14.56) for transmission to household contacts when a nasal-swab rapid test was used to identify the index case, compared to other test types. Use of nasal-swab rapid COVID-19 tests for initial detection of infection and initiation of infection control may be less effective at limiting transmission to household contacts than other test types.

Association between COVID-19 Vaccination and SARS-CoV-2 Infection among Household Contacts of Infected Individuals: A Prospective Household Study in England

“…Older household contacts were more often vaccinated, which might have led to less stringent self-isolation measures in these households. We also found a lower risk of infection in household contacts from larger households than those from smaller households, which is consistent with our early reports [ 27 , 28 ] but not with other studies [ 23 , 60 , 61 ]. While a positive association between household crowding and increased risk of infection [ 61 ] is intuitive, the explanation of an inverse association is more challenging and might be related to socioeconomic status, COVID-19 risk perception and behaviors [ 62 ], but the exact mechanism remains unclear.…”

The Asymptomatic Proportion of SARS‐CoV‐2 Omicron Variant Infections in Households: A Systematic Review

“…The three included studies were all based in the United States and were conducted from November 2021 to March 2022 (Table 1 ) [ 24 , 25 , 26 ].…”

“…Two studies were assessed as having a moderate risk of bias [ 24 , 25 ], and one study was assessed as having a high risk of bias [ 26 ] (Supporting Information S1 : Figure 1).…”

“…Ji et al. recruited households through the California Institute of Technology in California, USA, between November 2021 and March 2022 [ 26 ]. Only household members aged 6 years and older were included.…”