Meningococcal Disease in US Military Personnel before and after Adoption of Conjugate Vaccine

To the Editor: In their recent letter (1), Broderick et al. provided useful information about the remarkable declines in incidence of meningococcal disease among active-duty US military personnel since the early 1970s, when meningococcal vaccination began within that population. The authors reported that the incidence of meningococcal disease from vaccine-covered serogroups was 0.183 cases/100,000 persons during 2006–2013 among persons vaccinated with quadrivalent conjugate meningococcal vaccine (MCV-4), compared with 0.307 cases/100,000 persons during 2000–2013 among persons vaccinated with quadrivalent polysaccharide meningococcal vaccine (MPSV-4). They stated that, because these rates did not differ significantly, case rates were similar in personnel vaccinated with MCV-4 and MPSV-4. Although statistically correct, this comment might mislead the unwary reader.