Figure 6.

SIR of SARS-CoV-2 among household contacts, by age and SARS-CoV-2 lineage, California and Colorado, January to April 2021. To account for household clustering, ORs and 95% CIs were estimated using GEEs with an exchangeable correlation matrix and used to compare SIRs of household contacts to assess infection risk (the probability of infection among household contacts) by age group (pediatric vs adult) and lineage group (B.1.1.7 [Alpha] vs non-Alpha). Four pediatric and 45 adult household contacts reported prior SARS-CoV-2 infection or seropositivity and were excluded from the SIR calculations. Lineages were assigned to uninfected pediatric household contacts based on the lineage of the household primary case. Eleven uninfected pediatric household contacts did not have a lineage assigned because specimens from primary cases did not undergo sequencing.