Distributing vaccines to endemic areas challenging for health officials

ATLANTA — Increasing access to vaccines and implementing novel vaccination strategies may hold the key to reducing child mortality rates, according to a speaker here at the 2010 International Conference on Emerging Infectious Diseases.

Rana Hajjeh, MD, of the CDC, presenting on behalf of Carsten Mantel, MD, PhD, of WHO, said pneumonia alone causes about 2 million deaths annually in children aged younger than 5 years. Pneumococcal meningitis and meningitis caused by Haemophilus influenzae type b account for a considerable portion of these deaths, particularly in Asia and Africa, where vaccination rates remain low.

But data on vaccination rates are indicating some improvements.

Hib vaccines are being used in 165 countries compared with use in 120 countries 5 years ago. Many countries where Hib is endemic, including India, are introducing routine use of vaccine. Countries such as Indonesia and Nigeria are awaiting Global Alliance for Vaccines and Immunization approval but are taking steps toward introducing the pentavalent Hib vaccine.

The introduction of the pneumococcal conjugate vaccines is also benefiting developing countries, Hajjeh said.

A single-dose vial of the 10-valent pneumococcal conjugate vaccine was prequalified by WHO in 2009 but is not currently available through the Advance Market Commitments for vaccines; however, a two-dose vial is prequalified. The two-dose formulation does not contain a preservative, and it is unknown how this will affect its use. WHO also expects to prequalify a single-dose vial presentation of the 13-valent pneumococcal conjugate vaccine and aims to make it available through Advance Market Commitments by the fourth quarter of 2011. The difficulty with pneumococcal vaccines, however, is ensuring that the vaccine contains the predominant circulating serotypes of a given country, Hajjeh said, adding that storage and distribution pose challenges as well.

Health officials looking to routinely use rotavirus vaccines in developing countries face similar challenges.

Although the monovalent (RV1, RotaTeq, Merck) and the pentavalent (RV5, Rotarix, GlaxoSmithKline) rotavirus vaccines have led to reductions in severe disease, distributing the vaccine poses challenges to health care providers in the developing world. One problem is that rotavirus vaccines appear less effective in countries with the highest incidence of disease. Mitigating factors, including competing viruses, persistence of maternal antibodies and age of first dose, may affect the vaccines’ efficacy. However, Hajjeh said, several trials have indicated that even vaccines with reduced efficacy show promise in ameliorating severe illness.

Another vaccine that is “highly advocated” but not often administered in the developing world is the human papillomavirus vaccine. Despite efforts by public health officials, immunization rates remain low, with only 7% of the birth cohort having received the vaccine, Hajjeh said. High cost remains the major barrier to vaccination.

Typhoid and cholera vaccines, although less popular, also require discussion, Hajjeh said. Although both reduce disease burden, problems such as funding, limited duration of protection, identifying high-risk populations and strategies to reach them, or whether a vaccine is fit for routine use are preventing increased use of these vaccines.

Hajjeh said meningococcal serogroup A vaccine (MenAfriVac) has recently become available and aims to eliminate meningococcal disease in sub-Saharan Africa, where this disease is a “big problem.” – by Melissa Foster

For more information:

• Mantel C. B2. Presented at: 2010 International Conference on Emerging Infectious Diseases; July 11-14, 2010; Atlanta.