Evaluating COVID‐19 Transmission in a Series of Cases and Contacts in Three Municipalities of Colombia: Insights From the WHO First Few X Protocol, August 2020–January 2021

BACKGROUND: As part of the framework of preparedness and response to influenza viruses with pandemic potential, the World Health Organization (WHO) has developed a protocol for the characterization of a series of first cases and contacts of an agent with pandemic potential (FFX). At the end of 2019, PAHO/WHO invited Colombia to be among the pilot countries for implementing this protocol. It was conducted by the National Institute of Health of Colombia. METHODS: The WHO generic protocol was reviewed and adapted to Colombia. In its implementation, a series of 99 cases of COVID-19 and 360 total contacts (159 positive contacts) were evaluated between August 2020 and January 2021 in three municipalities of Colombia. Surveys were conducted, along with RT-PCR and antibody titer tests. Sociodemographic, clinical, and virological transmission conditions were analyzed to calculate the main epidemiological indicators of viral transmission using measures of central tendency and absolute and relative frequencies. RESULTS: A total of 258 cases were confirmed to be positive for COVID-19 for a secondary attack rate of 43%. The most common symptoms were cough, fever, headache, and odynophagia. The percentage of symptomatic contacts, clinical attack rate, incubation period, and serial interval were 34%, 16.2%, 4.6 days, and 4.7 days, respectively. CONCLUSIONS: The significant rate of infection and incubation periods among contacts was similar to those reported worldwide. The implementation of the WHO FFX protocol in a novel context allowed the country to test its capacity to implement global studies to determine early public health interventions. The study faced limitations due to the selection bias towards severe cases and challenges in case recruitment and contact tracing.