(HealthDay)—About one-third of Princeton University students given a vaccine to combat a meningitis B outbreak on campus in 2013 didn't show signs of protection against the infection eight weeks later, according to a study published in the July 21 issue of the New England Journal of Medicine.

Researchers at Princeton University, the University of Minnesota, and Public Health England tested blood samples collected from students eight weeks after the second dose of vaccine. Four hundred ninety-nine students received the recommended two doses of vaccine. The first was given in December 2013 and the second in February 2014.

The researchers note that none of the vaccinated students developed a meningitis infection. However, blood samples revealed that 33.9 percent of the students who received the two doses had no evidence of antibodies to the infection.

The results indicate "that we need to go further to understand how broadly protective this vaccine might be against the diversity of strains that can cause meningococcal disease, and especially meningococcal outbreaks," lead author Nicole Basta, Ph.D., of the University of Minnesota School of Public Health in Minneapolis, told HealthDay.

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