Secondary attack rate of COVID-19 in household contacts: a systematic review

Abstract

Objective COVID-19 is a novel virus with continuously evolving transmission trends. Contact tracing and quarantining of positive cases are chief strategies of disease control that has been accepted globally. Though scientific knowledge regarding household transmission of the COVID-19 through contact of positive case is sparse. Current systematic review was planned to assess global statistics and characteristics of household secondary attack rate (SAR) of COVID-19. Methods Eligible articles were retrieved through search of – MEDLINE, SCOPUS and EMBASE for the period December 2019 to June 15th 2020. Search terms were developed to identify articles reporting household SARs in various countries. After initial screening of 326 articles, 13 eligible studies were included in the final evidence synthesis. Results We found that SAR varies widely across countries with lowest reported rate as 4.6% and highest as 49.56%. The rates were unaffected by confounders such as population of the country, lockdown status and geographic location. Review suggested greater vulnerability of spouse and elderly population for secondary transmission than other household members. It was also observed that quarantining and isolation are most effective strategies for prevention of the secondary transmission of the disease. Symptomatic status of the index case emerged to be a critical factor, with very low transmission probability during asymptomatic phase. Conclusion Present review findings recommend that adequate measures should be provided to protect the vulnerable population as only case tracing and quarantining might be insufficient. It should be combined with advisory for limiting household contacts and active surveillance for symptom onset.

Hospital and Population-Based Evidences for COVID-19 Early Circulation in the East of France

“…The generation interval computed from intra-household data is close to what is published elsewhere [22][23] and the secondary attack rate is in a range consistent with previously publications [32]. In comparison, the secondary attack rate for influenza is much lower and estimated at 8% [21].…”

Clinical and Epidemiological Data of COVID-19 from Regensburg, Germany – A Retrospective analysis of 1084 consecutive cases

“…The definition of a close contact person was applied quite restrictively, nonetheless infection numbers were decreasing by beginning of April. An almost linear increase in the attack rate with age is consistent with other data [22]. Of course, these data are based on the assumption of linear spreading from known cases, which is certainly debatable for SARS-CoV-2.…”

Household Transmission of COVID-19: A Cross-Sectional Study

“…The study finding can be supported by the similar findings in the systematic review of various studies across the world which states that a large proportion (50-95%) of persons in contact with a COVID-19-positive case did not develop an infection, which points toward a potential role of inborn resistance to disease or natural immunity. 19 The other possible reason for having less transmission in the family may be due to the strict adherence of isolation guidelines released by the Ministry of Health & Family Welfare, Government of India. The guidelines clearly mentioned that as soon as the result of RT-PCR of a person is received as positive, the person is either admitted to the isolation facility or if the adequate rooms are available in the house, maybe allowed home isolation.…”

“…[13][14][15] Literature shows that secondary transmission or infection of SARS-CoV-2 in household contacts ranges from 4.6% to 49.56%. [16][17][18][19][20] WHO states that overcrowding or inadequate shelter are major contributors to the transmission of diseases like acute respiratory infections which can result in outbreaks or epidemic. 21 Literature search has revealed only two studies from India determining the secondary attack rate (SAR) among COVID-19 patients.…”