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Highlights • Serum IgG antibody responses developed in 95% of mildly symptomatic individuals by day 14 and all subjects had seroconverted by day 30. • Serum IgM and IgA antibody responses were lower and less frequent than corresponding IgG responses, and peaked and declined earlier 100% of mild symptomatic individuals developed an IgG antibody response by day 30. • Fewer than 45% of asymptomatic infected individuals had seroconverted by day 30 post-PCR diagnosis. • Impact on modeling of herd immunity., Objectives Studies on serologic responses following COVID-19 have been published primarily in individuals who are moderately or severely symptomatic, but there are few data from individuals who are mildly symptomatic or asymptomatic. Methods We measured IgG, IgM, and IgA to the receptor-binding domain of SARS-CoV-2 by ELISA in mildly symptomatic (n = 108) and asymptomatic (n = 63) on days 1, 7, 14, and 30 following RT-PCR confirmation in Bangladesh, and compared with pre-pandemic samples, including healthy controls (n = 73) and individuals infected with other viruses (n = 79). Results Mildly symptomatic individuals developed IgM and IgA responses by day 14 in 72% and 83% of individuals, respectively, while 95% of individuals developed IgG response, and rose to 100% by day 30. In contrast, individuals infected with SARS-CoV-2 but who remained asymptomatic developed antibody responses significantly less frequently, with only 20% positive for IgA and 22% positive for IgM by day 14, and 45% positive for IgG by day 30 after infection. Conclusions These results confirm immune responses are generated following COVID-19 who develop a mildly symptomatic illness. However, those with the asymptomatic infection do not respond or have lower antibody levels. These results will impact modeling needed for determining herd immunity generated by natural infection or vaccination.