Vaccination against meningococcal C ineffective in less than 2 years

Vaccination against meningococcal type C gives a high level of protection among students but would have no efficacy in less than two years, according to results of a study published in the journal "Clinical Infectious Diseases ".
The occurrence of a large number of infections caused by a virulent clone of Neisseria meningitidis resulted in a mass vaccination campaign in Quebec in 1992, recall Dr. Philippe De Wals and colleagues at the University of Laval.

They have studied 74 individuals who had contracted invasive meningococcal type C between the beginning of the immunization campaign and in 1998, they were compared with 285 people of the same age who did not develop the disease.

Just over half of the patients had been vaccinated (58.1%), against nearly three quarters (71.6%) controls.

During the first two years after vaccination, efficacy was 95% among children aged 6 and over, she fell to 77.3% in the three years after.

In children aged 2 to 5 years, vaccine efficacy was only 62% in the two years following its injection and became negative (-73.8%) during the three years after. And in less than 2 years, the vaccine seems never to have been effective, since according to the authors' estimates, the efficiency was 7.9% during the first study period and -390.5% in the second!

"The possibility of increased infection with meningococcal C resulting from the polysaccharide vaccine at an early age sensitivity can not be ruled out," says Dr. De Wals, suggesting "that both antibodies protective missing inhibition of antibody response may cause increased sensitivity to invasive disease. "