To supplement household clusters identified from address matching, we reviewed GAS clusters and outbreaks recorded on HP Zone and the reference laboratory outbreak database over the same period.
All household clusters were composed of 1 scarlet fever case and 1 iGAS case and occurred after March 2014.
Coupled with our observation that household clusters had a median size of 4 (compared with 3.9 for all households in England), it is unlikely the uncertainty about numbers of contacts could account for the increase in risk observed.
Two-step cluster analysis produced five household clusters defined in Table 1.
In the case of Kaunas, the results of binary logistic regression analysis are much more mixed and diverse than in the case of Vilnius, because sociodemographic characteristics (education and age), city area type and the interaction of area types and household clusters are significant factors.
Prophylaxis may have prevented several secondary cases, "but we still think our data are reasonably robust and represent the largest series of household clusters
Risk factors associated with secondary transmission were assessed with logistic regression, with an exchangeable correlation matrix to account for household clusters