Low vaccine efficacy of mumps component among MMR vaccine recipients in Chennai, India
Introduction of MMR vaccine was believed to have resulted in a decline in the incidence of measles, mumps and rubella infections. However, recent reports suggest the re-emergence of mumps infection worldwide in the vaccinated populations. It was proposed that the reason for this re-emergence was poor efficacy of MMR vaccine. The present study was aimed to investigate mumps infection in MMR vaccinated and non-vaccinated populations in Chennai, India. Blood samples were collected from acute mumps cases (n=74, 42<12 yr age, 54% males) and investigated for IgM antibody against mumps, IgG antibody against measles, mumps and rubella viruses by ELISA. Sixty seven (91%) patients had received MMR vaccine. All the 67 vaccinated cases were positive for parotitis, and mumps IgM. However, only 10 (15%) were positive for IgG. All samples (100%) were positive for rubella and measles IgG. These findings showed the occurrence of mumps infection among MMR vaccinated individuals in Chennai, India. The MMR vaccine failed to generate anti-mumps IgG. The reason may be low vaccine efficacy of the mumps component of the MMR vaccine used.