Table 3. Observed to Expected Analysis of Guillain-Barré Syndrome After the Ad26.COV2.S COVID-19 Vaccine^a.

Age groups, y	No.b	Vaccine doses administeredc	Person-yearsc	Background rate per 100 000 person-years	Expected cases	Rate ratio (95% CI)
Onset within 21 days after vaccination
All (≥18)	105	13 209 858	751 904	2	15.0	6.98 (5.71-8.45)
18-<65	91	11 169 018	635 740	2	12.7	7.16 (5.76-8.78)
18-29	3	2 388 973	135 980	0.88	1.2	2.51 (0.52-7.33)
30-39	10	2 277 609	129 641	1.07	1.4	7.21 (3.46-13.26)
40-49	22	2 345 471	133 504	1.29	1.7	12.77 (8.01-19.34)
50-64	56	4 156 965	236 614	2	4.7	11.83 (8.94-15.37)
≥65	14	2 040 840	116 164	2.4	2.8	5.02 (2.74-8.43)
Onset within 42 days after vaccination
All (≥18)	123	13 209 858	1 472 162	2	29.4	4.18 (3.47-4.98)
18-<65	105	11 169 018	1 244 722	2	24.9	4.22 (3.45-5.11)
18-29	4	2 388 973	266 237	0.88	2.3	1.70 (0.47-4.37)
30-39	12	2 277 609	253 826	1.07	2.7	4.42 (2.28-7.72)
40-49	25	2 345 471	261 389	1.29	3.4	7.41 (4.80-10.94)
50-64	64	4 156 965	463 270	2	9.3	6.91 (5.32-8.82)
≥65	18	2 040 840	227 440	2.4	5.5	3.30 (1.95-5.21)

^aIn this table, the results using the highest published background rates for each age group were used to illustrate the lowest observed to expected ratio, representing the most conservative estimate of the potential association with the vaccine.

^bReports with missing age, missing onset, or onset after 42 days are not included in these calculations. One report had missing age, sex, and onset information but was still deemed a valid report of Guillain-Barré syndrome. For 6 people, the onset time was more than 42 days: 62, 70, 75, 85, 89, or 94 days after vaccination.

^cCumulative Vaccine Administration Data.⁹ Please see the Methods section. Age-specific dose administration data were obtained from the Centers for Disease Control and Prevention and are shown with permission (F. Lee, MPH, statistician, Centers for Disease Control and Prevention, email September 3, 2021).