Figure 4. Household Secondary Attack Rates (SARs) by Contact Vaccination Status.

All index cases are included regardless of vaccination status. Point sizes (squares) are an inverse function of the precision of the estimates, and bars correspond to 95% CIs. Diamonds represent summary SAR estimates with corresponding 95% CIs. Heterogeneity indexes are as follows: Alpha (unvaccinated: I² = 92.5%; fully vaccinated: I² = 69.5%), Delta (unvaccinated: I² = 95.4%; partially vaccinated: I² = 30.4%; fully vaccinated: I² = 96.8%; booster vaccinated: I² = 76.5%), and Omicron (unvaccinated: I² = 97.1%; partially vaccinated: I² = 0.3%; fully vaccinated: I² = 60.1%; booster vaccinated: I² = 92.5%).