COVID-19 research briefs: rapid control of outbreak in Beijing; antibodies estimate infection fatality ratio in Iceland

Reference

Wu Z, Wang Q, Zhao J, et al. Time course of a second outbreak of COVID-19 in Beijing, China, June-July 2020. JAMA. Published online August 24, 2020. doi:10.1001/jama.2020.15894.

Synopsis

Research Brief #55: This research brief describes the response to an outbreak of COVID-19 in Beijing, China, that began in early June 2020. After 56 days of no new cases in Beijing, 3 people exposed to SARS-CoV-2 at a seafood market on June 3-4 were diagnosed as confirmed cases on June 11-12. The first case triggered an immediate response that included aggressive contact tracing, testing, movement restrictions, and quarantine of cases in a hospital. The seafood market was shut down on June 12, and all workers and residents of the surrounding community were tested. A total of 335 confirmed cases were identified, as were 33 asymptomatic infections; 93 persons were presymptomatic at the time of diagnosis. The peak of diagnosed cases was on June 13-14, and the last case was reported on July 5 after a period of relatively steady decline. The combination of a rapid response, extensive testing, quick results reporting, and comprehensive contact resulted in an impressive and rapid end to the outbreak. It is impossible to imagine this happening in the United States with our fragmented health system and underfunded public health infrastructure. Wu Z, Wang Q, Zhao J, et al. Time course of a second outbreak of COVID-19 in Beijing, China, June-July 2020. JAMA. Published online August 24, 2020. doi:10.1001/jama.2020.15894. Research Brief #56: This Icelandic study measured a variety of IgG and IgM antibodies to SARS-CoV-2 in 6 groups of Icelanders who had either never been tested or had tested negative, and 2 groups of Icelanders who had tested positive and had recovered. The authors weighted the sample by age and sex to estimate the number of Icelanders who had been infected, and used that to estimate the infection fatality ratio (deaths/[symptomatic + asymptomatic positives]) and case fatality ratio (deaths/symptomatic positives). Among patients who had experienced a symptomatic infection, IgG antibody levels remained stable over a 4-month period, which is encouraging in terms of at least medium-term immunity. Patients who smoked and those taking anti-inflammatory medications had lower antibody levels, although it is not clear whether this difference is clinically significant. This was not the case for IgM and IgA antibodies, which is what you would expect. The authors also estimate that the infection fatality ratio was 0.3% (95% CI 0.2% - 0.6%) and the case fatality ratio was 0.6% (0.3% - 1.0%). The infection fatality ratio was 0.1% (0.0% - 0.3%) in persons 70 years or younger, and 4.4% in those older than 70 years (1.9% - 8.4%). Gudbjartsson DF, Norddahl GL, Melsted P, et al. Humoral immune response to SARS-CoV-2 in Iceland. N Engl J Med. Published online August 24, 2020. doi: 10.1056/NEJMoa2026116.