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Current SARS-CoV-2 containment measures rely on controlling viral transmission. Effective prioritization can be determined by understanding SARS-CoV-2 transmission dynamics. We conducted a systematic review and meta-analyses of the secondary attack rate (SAR) in household and healthcare settings. We also examined whether household transmission differed by symptom status of index case, adult and children, and relationship to index case. We searched PubMed, medRxiv, and bioRxiv databases between January 1 and July 25, 2020. High-quality studies presenting original data for calculating point estimates and 95% confidence intervals (CI) were included. Random effects models were constructed to pool SAR in household and healthcare settings. Publication bias was assessed by funnel plots and Egger's meta-regression test. 43 studies met the inclusion criteria for household SAR, 18 for healthcare SAR, and 17 for other settings. The pooled household SAR was 18.1% (95% CI: 15.7%, 20.6%), with significant heterogeneity across studies ranging from 3.9% to 54.9%. SAR of symptomatic index cases was higher than asymptomatic cases (RR: 3.23; 95% CI: 1.46, 7.14). Adults showed higher susceptibility to infection than children (RR: 1.71; 95% CI: 1.35, 2.17). Spouses of index cases were more likely to be infected compared to other household contacts (RR: 2.39; 95% CI: 1.79, 3.19). In healthcare settings, SAR was estimated at 0.7% (95% CI: 0.4%, 1.0%). While aggressive contact tracing strategies may be appropriate early in an outbreak, as it progresses, measures should transition to account for setting-specific transmission risk. Quarantine may need to cover entire communities while tracing shifts to identifying transmission hotspots and vulnerable populations. Where possible, confirmed cases should be isolated away from the household.

We report the transmission dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) across different settings in Brunei. An initial cluster of SARS-CoV-2 cases arose from 19 persons who had attended the Tablighi Jama'at gathering in Malaysia, resulting in 52 locally transmitted cases. The highest nonprimary attack rates (14.8%) were observed from a subsequent religious gathering in Brunei and in households of attendees (10.6%). Household attack rates from symptomatic case-patients were higher (14.4%) than from asymptomatic (4.4%) or presymptomatic (6.1%) case-patients. Workplace and social settings had attack rates of <1%. Our analyses highlight that transmission of SARS-CoV-2 varies depending on environmental, behavioral, and host factors. We identify red flags for potential superspreading events, specifically densely populated gatherings with prolonged exposure in enclosed settings, persons with recent travel history to areas with active SARS-CoV-2 infections, and group behaviors. We propose differentiated testing strategies to account for differing transmission risk.

Guidance from many health authorities recommend that social distancing measures should be implemented in an epidemic when community transmission has already occurred. The clinical and epidemiological characteristics of COVID-19 suggest this is too late. Based on international comparisons of the timing and scale of the implementation of social distancing measures, we find that countries that imposed early stringent measures recorded far fewer cases than those that did not. Yet, such measures need not be extreme. We highlight the examples of Hong Kong and Brunei to demonstrate the early use of moderate social distancing measures as a practical containment strategy. We propose that such measures be a key part of responding to potential future waves of the epidemic.

On January 30, 2020, the World Health Organization (WHO) declared Coronavirus Disease 2019 (COVID-19) a “Public Health Emergency of International Concern”, and the disease now affects almost all countries and areas. Table 1 Challenges and opportunities of small countries in preparing for community transmission of COVID-19 Characteristics Challenges Opportunities Multiple land borders and high connectivity to other countries Vulnerable to multiple importation events Implementation of proportionate measures at point of entry Export of disease to other countries Travel and trade restrictions Collaboration with neighbouring countries for rapid exchange of information and joint risk assessment Lack of state capacity or prior experience in managing large outbreaks or natural disasters Infrequent activation of existing coordination mechanisms may result in over-reliance on strong interpersonal relationships for multi-agency working Ensure rationalisation of managerial responsibilities in crisis Institutional memory and resilience are more fragile Clarity on accountability for different plans and procedures, supplemented by documentation of processes to reinforce resilience Limited local health workforce and health service facilities Healthcare services may quickly become overwhelmed with demands for critical care beds and other equipment Health workforce can be redeployed in early phases of the epidemic to regain control Other non-COVID-19 health services may be neglected Contact tracing and quarantine measures can slow down epidemic progression Reliance on imports for PPE and essential medical supplies Supply chain disruptions and travel restrictions may limit availability of essential medical supplies to effectively manage the pandemic PPE and essential drug stockpiling during ‘peacetime’ can be augmented by regional collaboration and strong bilateral and multilateral relationships to ensure supply lines remain constant Information tends to spread quickly in smaller communities with multiple information sources False information may spread quickly and cause public panic, which can be difficult to control on unconventional platforms or social media Ensuring transparency and openness of information from health authorities that are responsive to public concerns Heterogeneous population and significant foreign worker population Different cultural expectations surrounding social distancing measures Engagement with community and religious leaders for targeted approaches Some groups such as foreign workers may be harder to reach Foreign missions can provide assistance in ensuring foreign worker access to health care PPE – personal protective equipment INCIDENT MANAGEMENT, PLANNING, AND MULTI-SECTORAL COORDINATION Brunei’s government is highly centralized and there is a dedicated budget allocation of BND15 million (US$10.5 million) for outbreaks and public health emergencies. [...]the lack of an updated resource map and resource-pooling arrangements hampered initial efforts. [...]there is a lack of clarity on responsibilities for securing operational logistic arrangements. The surveillance system leverages on digital patient records in the national health information management system database that links all health care facilities with near 100% penetration of the population.

IntroductionNeutralising antibodies (NAbs) have been shown to be correlative of immune protection against SARS-CoV-2. We report the protocol for a national longitudinal study to assess and compare the level of NAbs generated in response to COVID-19 vaccines in Brunei Darussalam in adults 2–6 weeks post primary series (BBIBP-CorV, AZD1222, or mRNA-1273 vaccines) and their subsequent follow-up after administration of a third (booster-1) dose (BBIBP-CorV, mRNA-1273, or BNT162b2).Methods and analysisParticipant data will be extracted and processed from the national electronic health record system (Bru-HIMS) and the national mobile health application (BruHealth) into a research data platform. Eligible adults who have received their primary or booster vaccine will be invited using a stratified random sampling strategy based on age, gender and vaccine type (baseline target population, n=3000; 2–6 weeks post last dose). Blood serum will be isolated, and NAb levels assessed using the cPass surrogate virus neutralisation test. Baseline participants will then be screened for eligibility for subsequent longitudinal analysis. Those who have received a third dose will be followed up at 1, 3, 6, 9 and up to 12 months. NAb levels will be evaluated across the participant population according to vaccine platform/booster type, time since the last dose and correlated with demographic data. The study period is from December 2021 to January 2023 and aims to evaluate how NAb levels wane following a third vaccine dose across different vaccine platforms and determine the impact and rate of breakthrough infections.Ethics and disseminationThis study has been approved by the Medical and Ethical Research Committee of Ministry of Health, Brunei Darussalam. Individual NAb test results will be shared with each participant by text message. The findings from this study will help policy-makers in Brunei develop future vaccination strategies and establish regulations across multiple agencies.

To the Editor Yu X & Yang R, and others have reported on asymptomatic transmission of SARS‐CoV‐2 at the familial level. 1‐3 We also note multiple reports of SARS‐CoV‐2–associated superspreading events (SSEs) arising from mass gatherings; however, the extent of transmission from asymptomatic carriers at these events has not been characterized. 4,5 Observational studies reporting a high household secondary attack rate and modest R0 suggest a transmission dynamic biased toward SSEs. 6 The presence of asymptomatic carriers could have implications for how relevant authorities handle mass gatherings. 9 Second, given the high proportion of asymptomatic individuals (models estimate 30%), our findings strengthen the argument for widespread testing at mass gatherings in areas of known community transmission. 10 These have the potential to become SSEs, and diagnostic delays can fuel exponential growth. 11 As countries begin to slowly relax restrictions from community “lockdowns,” widespread testing of participants at mass gatherings with consequent identification of asymptomatic carriers may allow for restrictions to be relaxed in a safe way. AUTHOR CONTRIBUTION Justin Wong: Conceptualization (lead); Data curation (lead); Formal analysis (equal); Investigation (equal); Supervision (lead); Visualization (supporting); Writing‐original draft (lead); Writing‐review & editing (equal).