Anthrax vaccination and risk of optic neuritis in the United States military, 1998-2003.

Background: Numerous case reports have suggested a possible association between optic neuritis and receipt of several different vaccines. The most frequently identified vaccines associated with optic neuritis in the literature are influenza and hepatitis B, and a report describing 2 US military cases suggests an association with the currently used anthrax vaccine (anthrax vaccine adsorbed).

Objective: To test the hypothesis that optic neuritis may be associated with anthrax, smallpox, hepatitis B, and influenza vaccines.

Design: We conducted a matched case-control study among US military personnel from January 1, 1998, through December 31, 2003, using the Defense Medical Surveillance System. Statistical associations between vaccine exposures and optic neuritis within 6-, 12-, and 18-week study intervals were estimated through multivariable conditional logistic regression analyses.

Subjects: A total of 1131 cases of optic neuritis and 3393 controls were matched by sex, military component, and deployment status.

Results: No statistically significant associations between optic neuritis and anthrax vaccine were observed for any of the 3 study intervals: 6-week interval (odds ratio [OR], 1.18; 95% confidence interval [CI], 0.74-1.87), 12-week interval (OR, 0.92; 95% CI, 0.63-0.35), and 18-week interval (OR, 0.81; 95% CI, 0.58-1.14). Furthermore, no difference in optic neuritis risk was detected when comparing those who received no dose, 1 dose, and 2 doses of anthrax vaccine. Similarly, no statistically significant associations were observed between optic neuritis and smallpox, hepatitis B, or influenza vaccines within any of the study intervals. No vaccine to vaccine interactions were statistically significant.

Conclusions: The results from this vaccine postmarketing surveillance investigation suggest that there is no association between optic neuritis and receipt of anthrax, smallpox, hepatitis B, or influenza vaccinations in the US military, whether these vaccines are administered alone or in combination. The negative findings presented here are important to the continuing discussions regarding the safety of these vaccines.