Table 1.

Quality of Published Observational Studies Included in the Review of 13-Valent Pneumococcal Conjugate Vaccine Effectiveness for Serotype 3 Invasive Pneumococcal Disease Using the Newcastle-Ottawa Scale

Study and Location	Study Design	Selection (x/4)	Comparability (x/2)	Exposure (x/3)	Overall (x/9)	Biasa
Study 1, United States [6]	Matched case-control	4	2	3	9	Low
Study 2, Spain [13]	Matched case-control	3	2	3	8	Low
Study 3, Germany [14]	Indirect cohort	4	2	2	8	Low
Study 4, United Kingdom [15]	Indirect cohort	4	2	2	8	Low

^aThe scale is categorized into 3 groups: selection, comparability, and outcome/exposure. A maximum of 9 points may be awarded to each study as follows: 4 for selection, 2 for comparability, and 3 for outcome/exposure. Bias was scored as high (0 in any of the categories), moderate (1 in any category), and low (≥2 in all categories).