Fig. 3: RT-qPCR Ct values in the randomly diagnosed (asymptomatic) SARS-CoV-2 infections.

Distribution of these Ct values (blue circles) in the six pairwise comparisons between primary infections in unvaccinated individuals, reinfections in unvaccinated individuals, BNT162b2-vaccine breakthrough infections, and mRNA-1273-vaccine breakthrough infections, a–f. A randomly diagnosed infection was defined as an RT-qPCR-positive test conducted with no prior reason to suspect infection and no reported presence of symptoms compatible with a respiratory tract infection. That is, the RT-qPCR test was conducted as part of a survey (random testing campaigns), for routine healthcare testing, for pre-travel requirement, or at port of entry upon arrival in Qatar. a includes, in each comparison group, n = 1584 biologically independent samples, b includes n = 158 biologically independent samples, c includes n = 140 biologically independent samples, d includes n = 987 biologically independent samples, e includes n = 421 biologically independent samples, and f includes n = 60 biologically independent samples, each over 1 experiment. Boxplots center lines indicate the median Ct values, box limits indicate the 25% and 75% quartiles, and whiskers indicate maximum and minimum observations within 1.5 of interquartile range. Paired t tests were used to compare the difference in means between study groups, with no adjustment for multiple comparisons. Two-sided p-values are reported.