Table 2.

Comparison of studies assessing the degree of reduction in risk of breakthrough infection compared to primary infection (namely, the protective effects of vaccine-induced immunity).

Setting	Percent Reduction in Breakthrough Infection	Country	Sample Size	Follow-Up
Rovida et al. [43]	0.86	Italy	4066	3.7 months
Santacatterina et al. [44]	0.91	USA	3975	3.9 months
Fowlkes et al. [45]	0.8	USA	7112	8 months
Naito et al. [46]	0.765	Japan	8749	6 months
weighted average	0.8159