Meningococcal combo vaccine not successful in U.K. infants

May 2005

A combination vaccine developed to reduce the number of vaccines infants receive appears to provide less immunity than the vaccines administered individually, according to a study in the Journal of the American Medical Association (JAMA).

The researchers concluded, “These results highlight the unpredictability of immune responses to individual vaccine antigens after incorporating multiple antigens into combination vaccines and underline the importance of assessing the immunogenicity of all coadministered vaccine antigens in prelicensure trials. The Pnc9-MenC vaccine as tested may not be a suitable replacement for individual MenC or pneumococcal glycoconjugate vaccine.”

Jim P. Buttery, FRACP, formerly of the University of Oxford, Churchill Hospital, Headington, Oxford, U.K., and colleagues, conducted a study to determine the immunogenicity and safety of a combination nine-valent pneumococcal-group C meningococcal conjugate candidate vaccine (Pnc9-MenC). The phase 2 randomized controlled trial was conducted from August 2000 to January 2002 and enrolled 240 healthy infants ages 7 to 11 weeks from two centers in the United Kingdom, with home follow-up visits at ages 2, 3, 4, and 5 months.

Individual vaccine proves better

Infants received Pnc9-MenC (n = 120) or monovalent group C meningococcal conjugate vaccine (MenC) (n = 120) administered in addition to routine immunizations (diphtheria and tetanus toxoids and whole-cell pertussis [DTwP], Haemophilus influenzae type b (Hib) polyribosylribitol phosphate-tetanus toxoid protein conjugate, oral polio vaccine).

The researchers concluded “Pnc9-MenC combination vaccine administered to infants at ages 2, 3, and 4 months demonstrated reduced group C meningococcal immunogenicity compared with MenC vaccine. The immunogenicity of concomitantly administered Hib and DTwP vaccines was also diminished. The Pnc9-MenC vaccine was safe and immunogenic for all contained pneumococcal serotypes.”

The researchers concluded that, “These results highlight the unpredictability of immune responses to individual vaccine antigens after incorporating multiple antigens into combination vaccines and underline the importance of assessing the immunogenicity of all coadministered vaccine antigens in prelicensure trials. The Pnc9-MenC vaccine as tested may not be a suitable replacement for individual MenC or pneumococcal glycoconjugate vaccines.”

Combo vaccines

Since the introduction of a MenC vaccine into routine immunization schedule in the United Kingdom in November 1999, group C meningococcal disease has decreased by 87% in the ages targeted for vaccination, with estimated vaccine efficacy of 90%, according to a JAMA press release.

Within two years of the introduction of a seven-valent pneumococcal glycoconjugate vaccine (PCV7, Prevnar, Wyeth) into the recommended infant schedule in the United States, there was a 69% reduction in culture-positive invasive pneumococcal disease in children younger than age 2.

The advent of these vaccines has increased pressure on crowded infant immunization schedules. Infants in the United States receive up to 20 separate vaccine injections over five immunization encounters at ages 2, 4, 6, 12, and 18 months to protect against disease.

The combining of pneumococcal and meningococcal conjugate vaccines has the potential to spare U.S. infants up to four extra injections by age 18 months and to decrease parental and clinician concerns about the number of vaccinations.

For more information:

• Buttery JP, Riddell A, McVernon J, et al. Immunogenicity and safety of a combination pneumococcal-meningococcal vaccine in infants. JAMA. 2005:293(14);1751-1758.