At age 18 weeks , there were no differences in opsonophagocytic activity between the 2 +1 and 3 +0 groups for reciprocal titres of at least 8 , but at age 10 months , proportions with an opsonophagocytic reciprocal titre of at least 8 for serotypes 1 , 4 , 5 , 6B , 18C , 19F and 23F were higher in the 2 +1 group than in the 3 +0 group .